Sentinel-5/UVNS
Author(s):
J. Irizar;
M. Melf;
P. Bartsch;
J. Koehler;
S. Weiss;
R. Greinacher;
M. Erdmann;
V. Kirschner;
A. Perez Albinana;
D. Martin
Show Abstract
Sentinel-5/UVNS instrument is an Earth atmospheric monitoring spectrometer developed within the Copernicus program. The mission objective is to monitor the chemical composition of the Earth’s atmosphere on a daily basis. Airbus Defense and Space GmbH acts as the prime contractor for the instrument under a European Space Agency contract.
The current paper will focus on four themes. First it will provide a brief historical and technical overview of the Sentinel-5/UVNS instrument. Second, the key design drivers will be described. Third, the key optical technologies carried on board the instrument will be elaborated. Finally, the paper concludes with a short look at the current state of the instrument’s development cycle.
IASI-NG development status
Author(s):
Bertrand Calvel;
Frederic Bernard
Show Abstract
The Infrared Atmospheric Sounding Interferometer New Generation (IASI-NG) is a key payload element of the second generation of European meteorological polar-orbit satellites (METOP-SG) dedicated to operational meteorology, oceanography, atmospheric chemistry, and climate monitoring.
It will continue and improve the IASI mission in the next decades (2020-2040) in the field of operational meteorology, climate monitoring, and characterization of atmospheric composition related to climate, atmospheric chemistry and environment. The performance objective is mainly a spectral resolution and a radiometric error divided by two compared with the IASI first generation ones.
The measurement technique is based on wide field Fourier Transform Spectrometer (operating in the 3.5 - 15.5 μm spectral range) based on an innovative Mertz compensated interferometer to manage the so-called self-apodisation effect and the associated spectral resolution degradation.
We present here the design of the instrument, the development status of the main units, critical technologies and subsystems and the first test results performed on engineering models.
The hyperspectral instrument onboard EnMAP: overview and current status
Author(s):
Manuela Sornig;
Sebastian Fischer;
Christian Chlebek;
Martin Muecke;
Hans-Peter Honold;
Brian Heider
Show Abstract
The Environmental Mapping and Analysis Program (EnMAP) is a German spaceborne science mission that aims at characterizing the Earth’s environment on a global scale. The single payload of the satellite is the hyperspectral imager (HSI). It is capable of measuring the solar radiance reflected from the Earth’s surface as a continuous spectrum in the spectral range of 420nm to 2450nm, with a spectral sampling of 6.5nm (VNIR) and 10nm (SWIR). The EnMAP on ground swath of 30km is sampled with 30m.
The instrument features a telescope with a 18cm aperture. A double-slit splits the field of view into the two separate fields for VNIR and SWIR. Two spectrometers disperse the light using large, curved prisms and collect the light in an Offner configuration onto the VNIR and the SWIR detector. In addition, the instrument features calibration capabilities using a deployable, full aperture solar diffuser in front of the telescope and on-board calibration sources that can be fed into the spectrometers. The instruments demanding requirements on thermal stability are covered by an active thermal control of the whole instrument using loop-heat pipes.
In this proceeding, we give a short overview on the design, application and current integration status of the mission, which is currently in Phase D. The focus is on the important steps recently accomplished or currently ongoing, specific on the:
• completion of the telescope setup
• assembly of the spectrometers with the optical components of both spectrometer paths already in place, aligned and successfully characterized
• setup and characterization of the on-board calibration source OBCA
• integration of the calibration chain including the above mentioned OBCA into the spectrometer
• implementation of the first of the two front end devices, the VNIR camera and the SWIR camera
• assembly of the platform
The present situation suggests an EnMAP launch by the end of 2020.
Active optics for next generation of space observation instruments
Author(s):
T. Viard;
J. -F. Blanc;
C. Devilliers;
F. Champandard;
B. Bailly;
F. Falzon;
J. -B. Ghibaudo;
D. Sucher;
G. Briche;
V. Costes;
C. Du Jeu
Show Abstract
Thales Alenia Space has been involved in the design and the development of space observation instruments for over 40 years. This paper will explain why active optics is needed for next generation of instruments for Earth observation. We will also describe what kind of solution is preferred and why. We will give an overview of the development status on the associated technologies. Indeed, the future missions will have to deal with better performance, better optical quality while from manufacturing point of view, the total mass, the development schedule and the final cost have to be reduced. These constraints induce a new generation of solutions based on large entrance optics associated to high lightweight ratio which naturally provide solutions sensitive to gravity deformation. In these conditions, the enhancement of the final performance can only be guaranteed by using active optics in flight. A deformable mirror is therefore foreseen to be implemented in future large telescopes in order to correct manufacturing residues, ground/flight evolution including gravity. Moreover, low mass and low cost require more compact designs which entail solutions more sensitive to misalignment. An active positioning mechanism is then also needed in order to correct the telescope alignment during operation conditions. Thales Alenia Space has been selected by CNES to develop and qualify active optics building blocks and then to test and demonstrate the improvement that new active technologies can bring in a full size instrument representative of the next generation of observation instruments. An overview of the current development status and the achievable performances is given.
A novel deployable telescope to facilitate a low-cost <1m GSD video rapid-revisit small satellite constellation
Author(s):
David Gooding;
Guy Richardson;
Andrew Haslehurst;
David Smith;
Chris Saunders;
Guglielmo Aglietti;
Roy Blows;
Jason Shore;
Karen Hampson;
Martin Booth
Show Abstract
The multi-billion dollar Earth observation applications market continues to demand better spatial and temporal resolution; simply put, this means bigger apertures and more satellites. This paper describes a novel deployable telescope that addresses the market needs for a <1m GSD imager in a small launch volume. This system will allow many identical satellites to be launched into a constellation from a single launch vehicle, providing a low-cost solution to rapid-revisit high resolution imaging requirements. Alternatively, two or three satellites could be launched in a dedicated small satellite launch vehicle, where previously only one would have fit.
Surrey Satellite Technology Ltd. (SSTL) has already demonstrated low-cost 1m GSD imagery from the Carbonite-2 platform, but the deployable telescope solution presented here provides the opportunity to build on this capability by significantly improving revisit time, without the typical increase in cost.
SSTL is developing, alongside the Surrey Space Centre (SSC) and the Dynamic Optics and Photonics Group at the University of Oxford, a telescopic deployable structure and a fine alignment system to align the Cassegrain-type telescope in-orbit. The three-concentric barrel deployable structure and mechanisms are discussed including the associated requirements and trade-off study that led to this design.
The dynamic nature of this system exacerbates traditional optical challenges such as alignment and stray light control; solutions to these are proposed, the optical design rationale is explained and predicted imaging performance shown. The novel autonomous fine alignment system, both algorithms and mechanisms, is presented. The last section deals with the spacecraft level implications and accommodation. Then finally the constellation level system design is shown with regards to the launch vehicle options and orbit configuration for coverage optimization; both global and target-specific.
Active correction system of a deployable telescope for Earth observation
Author(s):
Dennis Dolkens;
Gijsbert Van Marrewijk;
Hans Kuiper
Show Abstract
Deployable optics can bring major cost reductions to the field of Earth Observation. One of the key challenges in the development of a deployable optical system, however, is making sure that it can meet its performance targets following its deployment. In this paper, a novel active correction system for a deployable telescope is described. The correction system co-aligns and phases the primary mirror segments and subsequently corrects remaining aberrations using a deformable mirror. A novel phasing sensor called PistonCam can bring telescope segments into phase while the telescope is staring at extended scenes. By only sampling segment boundaries, PistonCam is able to isolate piston and tip/tilt errors which allows the errors to be corrected more effectively. After phasing process has been completed, a moving scene sharpness optimization technique is used to correct the remaining aberrations with a deformable mirror, The technique does not require a constant scene, unlike existing sharpness optimization techniques. As such, the telescope does not need to track a ground scene during the correction process. The technique can also be used for continuous correction of telescope deformations. The active optics system offers robust aberration correction, is computationally inexpensive and requires limited additional optical hardware.
On orbit real-time position and attitude metrology of long focal length optical system
Author(s):
Yun Wang;
Xiaoyong Wang;
Yongli Hu;
Shaoyuan Cheng
Show Abstract
The urgent need for the precise, real-time position metrology between the optical components in a modern space camera is becoming more critical with the increased resolution, aperture, focal length, and light-weighted structure. Gravity offload, composite material humidity desorption, temperature cyclical variation with the illumination, and micro-vibration on platform would introduce unpredictable affect to decrease the imaging quality. The solution of the optical system disorders would mainly rely on the ground-based stimulation and on that basis, active optics compensation, which could not be accurate. This influence expands within the opto-mechanical structure complexity. This paper represents an implement solution for position and attitude metrology used for on-orbit real-time measurement. To deal with the contradiction of system accuracy and simplicity, we simplified the system to a measurement model equivalent to 6 degree of freedom Stewart Platform structure. The works on this paper tightly coupled to the accuracy requirement of a long focal length optical system. After carefully compare the systematic requirement and balance the implementation costs, we applied the common-path, multi-channel heterodyne interferometers to accomplish the large-scaled coarse measurement for the step disturbance and small-range fine measurement to sense the ambient vibration. The metrology accuracy analysis and error evaluation indicated an effectiveness of this metrology system, which met the requirement of our given optical system. It was indicated in this paper that the metrology method could be generalized in other optical systems and similar long focal length optical systems in the future.
A new laser technology for LISA
Author(s):
Katrin Dahl;
Pelin Cebeci;
Oliver Fitzau;
Martin Giesberts;
Christian Greve;
Markus Krutzik;
Achim Peters;
Sana Amairi Pyka;
Jose Sanjuan;
Max Schiemangk;
Thilo Schuldt;
Kai Voss;
Andreas Wicht
Show Abstract
Within the European Space Agency (ESA) activity “Gravitational Wave Observatory Metrology Laser” we designed a laser head to fulfill the LISA laser requirements using a non-NPRO seed laser technology: an external cavity diode laser (ECDL) with resonant optical feedback from an external cavity as master oscillator for further linewidth narrowing. Furthermore, our design features a single-stage fiber amplifier with an amplification factor of about 20 dB. This paper covers the requirements on the laser source for LISA, the design and first results of performance characterization of the laser head breadboard.
LISA laser system and European development strategy
Author(s):
B. Shortt;
L. Mondin;
P. McNamara;
K. Dahl;
S. Lecomte;
Pedro Duque
Show Abstract
The Laser Interferometer Space Antenna (LISA), with its extreme distance measurement requirements (pm over arm lengths of 2.5 million km), imposes many stringent requirements on the laser systems used for the distance metrological measurements. In particular, frequency and power stability, sideband phase noise, and frequency reproducibility, the need of manufacturing multiple laser systems and extremely challenging lifetime (extended mission duration of 12.5 years) which demand a streamlined laser design and a particular attention to reliability and procurement strategy, all pose a significant challenge. The main requirements will be presented and analysed. Some preliminary strategies as it pertains to procurement and lot screening shall also be approached.
The current configuration and break-down of the future on-board laser systems shall be provided detailing in particular the critical interfaces.
Existing space heritage hardware (such as the LISA Pathfinder Master Oscillator) and new specialized developments are under study in both Europe and the US. European industry is developing custom Power Amplifiers to reach the end-of-life requirement of 2W (in Continuous Wave operation). In parallel alterative possible sources for a back-up Master Oscillator are also being investigated, based on off the shelf components and proprietary technologies. An overview of the development strategy shall be presented as well as some details on the specific hardware.
Progress and plans for a U.S. laser system for the LISA mission
Author(s):
Kenji Numata;
Anthony Yu;
Hua Jiao;
Scott Merritt;
Frankie Micalizzi;
Molly Fahey;
Jordan Camp;
Michael Krainak
Show Abstract
NASA Goddard Space Flight Center is developing a master oscillator power amplifier (MOPA) laser transmitter for the ESA-led Laser Interferometer Space Antenna (LISA) mission. Taking advantage of our space laser experience and the emerging telecom laser technology, we are developing a full laser system for the LISA mission. Our research effort has included both master oscillator (MO) and power amplifier (PA) developments, and their environmental testing and reliability for space flight. Our current baseline for the MO is a low-mass, compact micro non-planar ring oscillator (m- NPRO) laser. The amplifier uses a robust mechanical design based on fiber components. We have performed laser system noise tests by amplitude- and frequency-stabilizing the PA output. We will describe our progress and plans to demonstrate a TRL 6 laser system, which is an essential step toward qualifying lasers for space applications, by 2021.
Diode-pumped Alexandrite laser instrument for next generation satellite-based Earth observation
Author(s):
Michael Strotkamp;
Alexander Munk;
Bernd Jungbluth;
Hans-Dieter Hoffmann;
Josef Höffner
Show Abstract
In this work the first diode-pumped Alexandrite ring laser in Q-switched single-longitudinal mode (SLM) operation is presented. A carefully designed and complex ring resonator with several functional components is combined with an innovative pumping scheme with high-power red laser diodes.
The spectral and energetic suitability of a first laser was demonstrated in hundreds of operating hours and, with a novel mobile lidar system, by the first measurements in the atmosphere by means of a diode-pumped Alexandrite laser, yielding data from the stratosphere to the mesosphere.
An improved laser yields a pulse energy of 1.7 mJ at a repetition rate of 500 Hz with an excellent beam quality of M
2 < 1.1. By seeding the resonator with a narrow-band diode laser, SLM operation with a linewidth below 4 MHz is achieved. The electro-optical efficiency of 2 % is the highest archived for all Alexandrite lasers in SLM operation and reasonable for space-operation.
The performance analysis as well as benchmarking with the space-qualified mounting technology point out the TRL and the remaining effort of development of the technology.
ESAs ScyLight Programme: activities and status of the high throughput optical network "HydRON"
Author(s):
Harald Hauschildt;
Carlo Elia;
Andrew Jones;
Hermann Ludwig Moeller;
Josep Maria Perdigues Armengol
Show Abstract
ESA's Telecommunications and Integrated Applications Directorate (TIA) runs a dedicated programmatic framework to Optical Communication Technologies, called ARTES ScyLight (SeCure and Laser communication Technology, pronounced "skylight").
ScyLight supports the development and deployment of innovative optical technologies for satellite communication as well as assisting industry to develop new market opportunities for optical communication technologies.
The ScyLight programme focuses the efforts of European and Canadian industry on optical communication technologies in the following areas:
•Optical Communication Technology at System Level
•Optical Communication Terminal Technology
•Intra-Satellite Photonics/Optical Payloads
•Quantum Cryptography Technologies in Space and initial services demonstration
The paper will give an overview of the programme status and an outlook on its evolution.
The paper will inform about the status of a new proposed ESA project on optical communications called “High thRoughput Optical Network” (HydRON), which aims to demonstrate European and Canadian capabilities in all fields of optical communications and with the seamless integration into terrestrial network structures, via a dedicated mission.
Optical communications systems for NASA's human space flight missions
Author(s):
Antonios Seas;
Bryan Robinson;
Tina Shih;
Farzana Khatri;
Mark Brumfield
Show Abstract
The Laser-Enhanced Mission Communications Navigation and Operational Services (LEMNOS) office at Goddard Space Flight Center (GSFC) manages two NASA optical communication related projects, the Orion EM-2 Optical Communications Terminal (O2O) and the Integrated Laser Communications Relay Demonstration (LCRD) Low-Earth Orbit (LEO) User Modem and Amplifier Terminal (ILLUMA-T) projects. The main goal of LEMNOS is the advancement and implementation of optical communications systems and technologies for NASA missions. The O2O mission is sponsored by NASA’s Human Exploration and Operations (HEO) Mission Directorate. The O2O project will provide optical communications capability to the Orion series of spacecraft, starting with the demonstration of operational utility on EM-2. It will be the first time a human exploration mission will rely on optical communications for its high-bandwidth link. ILLUMA-T is sponsored by the Space Communications and Navigation (SCaN) Program Office. It is destined for the International Space Station (ISS) as an external payload attached to the Japanese Experiment Module - Exposed Facility (JEM-EF). The ILLUMA-T project is developing an optical communications user terminal to demonstrate high bandwidth data transfer between LEO and the ground through the geosynchronous LCRD relay. ILLUMA-T will be the first demonstration of a LEO user of the LCRD system, pointing and tracking from a moving spacecraft at LEO to GEO satellite and vice versa, end-to-end operational utility of optical communications, and 51 Mbps forward link to ISS from ground. Both projects are collaborations between GSFC, Massachusetts Institute of Technology – Lincoln Laboratory (MIT-LL), and a number of contractors.
Update on DLR's OSIRIS program
Author(s):
Christian Fuchs;
Christopher Schmidt
Show Abstract
Optical satellite downlinks have gained increasing attention throughout the last years. Especially for the application of optical satellite downlinks, DLR's Institute of Communications and Navigation is developing a number of payloads for various satellites. Within the OSIRIS program, DLR develops experimental optical terminals and systems which are optimized for small satellites.
This presentation will give an update on DLR's existing payloads (i.e. on the satellites Flying Laptop and BIROS, which have been launched in 2017 and 2016, respectively). First results will be presented. Furthermore, an outlook to planned missions will be given. This includes OSIRIS4Cubesat, which is planned for launch in Q4/2018, and OSIRISv3, which will be installed at the Airbus DS Bartolomeo platform aboard the ISS in 2019.
Optical communications downlink from a 1.5U Cubesat: OCSD program
Author(s):
T. S. Rose;
D. W. Rowen;
S. LaLumondiere;
N. I. Werner;
R. Linares;
A. Faler;
J. Wicker;
C. M. Coffman;
G. A. Maul;
D. H. Chien;
A. Utter;
R. P. Welle;
S. W. Janson
Show Abstract
In this presentation, we discuss the first demonstration of a lasercom downlink from a LEO 1.5U 2.3 kg CubeSat to our optical ground station at The Aerospace Corporation in El Segundo, CA. Two vehicles, AC7-B&C, built under NASA’s Optical Communications and Sensors Demonstration (OCSD) program and described in previous presentations, were launched in November 2017 and placed in a 450-km circular orbit. Following on-orbit checkouts and preliminary pointing calibration utilizing on-board star trackers, we have demonstrated (at the time of this manuscript submission) communications links up to 100 Mbps with bit error rates near 10-6 without any forward error correction. Further optimization of the vehicle pointing and detection electronics and operating the transmitter at its full power capacity should enable performance improvements and potential for higher data rates.
Optical satellite communication space terminal technology at TNO
Author(s):
Rudolf Saathof;
Will Crowcombe;
Stefan Kuiper;
Nick van der Valk;
Federico Pettazzi;
Dorus de Lange;
Peter Kerkhof;
Martijn van Riel;
Harry de Man;
Niel Truyens;
Ivan Ferrario
Show Abstract
Optical communications will complement radio frequency (RF) communications in the coming decades to enhance throughput, power efficiency and link security of satellite communication links. To enable optical communications technology for intersatellite links and (bi-directional) ground to satellite links, TNO develops a suite of technologies in collaboration with industry, which comprises of terminals with different aperture sizes, coarse pointing assemblies and fast steering mirrors. This paper presents the current state of the development of TNO technology for optical space communications. It mainly focuses on the development of an optical head with an entrance aperture of 70 mm, an optical bench for CubeSats and coarse pointing assemblies (CPAs). By continuing these steps, world wide web based on satellite communications will come closer.
SPEXone: a compact multi-angle polarimeter
Author(s):
Aaldert van Amerongen;
Jeroen Rietjens;
Jochen Campo;
Ersin Dogan;
Jos Dingjan;
Raj Nalla;
Jerome Caron;
Otto Hasekamp
Show Abstract
We have developed a 6 dm3-sized optical instrument to characterize the microphysical properties of fine particulate matter or aerosol in the Earth atmosphere from low Earth orbit. Our instrument can provide detailed and worldwide knowledge of aerosol amount, type and properties. This is important for climate and ecosystem science and human health [1, 2]. Therefore, NASA, ESA and the European Commission study the application of aerosol instruments for planned or future missions. We distinguish molecular Rayleigh scattering from aerosol Mie-type scattering by analyzing multi-angle observations of radiance and the polarization state of sun light that is scattered in the Earth atmosphere [3]. We measure across the visible wavelength spectrum and in five distinct viewing angles between -50° and +50°. Such analysis has been traditionally done by rotating polarizers and band-filters in front of an Earth observing wide-angle imager. In contrast, we adopt a means to map the linear polarization state on the spectrum using passive optical components [4]. Thereby we can characterize the full linear polarization state for a scene instantaneously. This improves the polarimetric accuracy, which is critical for aerosol characterization, enabling us to distinguish for example anthropogenic from natural aerosol types. Moreover, the absence of moving parts simplifies the instrument, and makes it more robust and reliable. We have demonstrated this method in an airborne instrument called SPEX airborne [5, 6] in the recent ACEPOL campaign together with a suite of state-of-the art and innovative active and passive aerosol sensors on the NASA ER-2 high-altitude research platform [7]. An earlier report on the SPEX development roadmap was given in [8]. In this contribution we introduce SPEXone, a compact space instrument that has a new telescope that projects the five viewing angles onto a single polarization modulation unit and the subsequent reflective spectrometer. The novel telescope allows the observation of five scenes with one spectrometer, hence the name. We describe the optical layout of the telescope, polarization modulation optics, and spectrometer and discuss the manufacturability and tolerances involved. We will also discuss the modelled instrument performance and show preliminary results from optical breadboards of the telescope and polarization modulation optics. With SPEXone we present a strong and new tool for climate research and air quality monitoring. It can be used to study the effect of atmospheric aerosol on the heating/cooling of the Earth and on air quality. Also, SPEXone can improve the accuracy of satellite measurements of greenhouse gas concentrations and ocean color that rely on molecular absorption of reflected sunlight by providing detailed knowledge of the aerosol properties, required to accurately trace the light path in presence of scattering.
SPEXone is developed in a partnership between SRON Netherlands Institute for Space Research and Airbus Defence and Space Netherlands with support from the Netherlands Organisation for Applied Scientific Research (TNO) as a Dutch contribution to the NASA PACE observatory launching in 2022.
The European CO2 Monitoring Mission: observing anthropogenic greenhouse gas emissions from space
Author(s):
Bernd Sierk;
Jean-Loup Bézy;
Armin Löscher;
Yasjka Meijer
Show Abstract
Responding to plans of the European Commission for extending the observation capabilities of the Copernicus programme, the European Space Agency (ESA) has initiated Phase A industrial (technical feasibility) studies for several new space-borne Earth Observation missions. High priority is given to a constellation of LEO satellites in Sunsynchronous orbit with the purpose of observing anthropogenic carbon dioxide (CO2) emissions [European Commission, 2017]. The observing system shall acquire images of CO2 concentration in terms of dry air column-averaged mole fractions (XCO2), providing complete global land coverage at high spatial resolution (4 km2) within five days. The demanding requirements call for a payload comprising a combination of multiple instruments, which perform simultaneous measurements. The XCO2 is inferred from reflectance measurements in the Near-Infrared (NIR) and Short-Wave Infrared spectral regions (SWIR). This requires at least three spatially co-registered push-broom imaging spectrometers, measuring spectral radiance and solar irradiance in the NIR (747-773 nm), SWIR-1 (1595-1675 nm) and SWIR-2 (1990-2095 nm) at moderate spectral resolving power (R~5000-7000). In addition, the observations for CO2 concentration will be complemented by Differential Optical Absorption Spectroscopy (DOAS) measurements of nitrogen dioxide (NO2) over the same area. The NO2 measurements in the visible region (400-500 nm) are expected to serve as a tracer for plumes of high CO2 concentration resulting from high temperature combustion, which will facilitate plume identification and mapping. The third component of the payload is a multiple-angle polarimeter (MAP), performing high-precision measurements of aerosol (and cloud) properties. Its measurements of polarized radiance under various observation angles are expected to reduce XCO2 bias error and significantly increase the yield of useful retrievals from the NIR and SWIR spectra. The complex observation architecture, involving multiple instruments and platforms, call for optimized observational requirements, driven by the primary goal of detecting and quantifying point-sources of greenhouse gas emissions. In particular, high single-sounding precision is essential for identifying plumes of elevated CO2 concentration from instantaneous image acquisitions without regional and temporal averaging. This translates into stringent requirements for Signal-to-noise ratio (SNR), as well as spatial co-registration and spectral stability, which drive the instrument design. The presentation will introduce the different elements of the candidate Copernicus mission, in view of the ambitious mission goals. The payload components and observation requirements are addressed with special emphasis on the derivation of the SNR and spectral resolution requirements, which determine the instrument sizing.
In-flight validation of SPEX airborne spectro-polarimeter onboard NASA's research aircraft ER-2
Author(s):
J. Martijn Smit;
Jeroen H. H. Rietjens;
Antonio di Noia;
Otto P. Hasekamp;
Wouter Laauwen;
Brian Cairns;
Bastiaan van Diedenhoven;
A. Wasilewski
Show Abstract
High accuracy multi-angle polarimetry is of crucial importance for remote sensing of aerosol and cloud properties with accuracies demanded by climate and air quality studies. In this contribution, we provide an detailed description of the multi-angle spectro-polarimetric instrument “SPEX airborne” that was developed to operate from NASA’s high altitude research aircraft ER-2. SPEX airborne delivers measurements of radiance and linear polarization at nine fixed viewports with angles equally distributed over at total angular range of 112°, at visual wavelength in the range 400-760nm. Each viewport acts as a pushbroom spectrometer with a swath of 6°. SPEX airborne participated in the recent the ACEPOL campaign in October-November 2017 when it flew together with NASA’s Research Scanning Polarimeter (RSP), the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI), and the Airborne Hyper-Angular Rainbow Polarimeter (AirHARP). We compare polarimetric and radiometric measurements from SPEX airborne with those collected by RSP at four visible wavelength bands. Simultaneous measurements were made while flying over widely different scenes, under different illumination and meteorological conditions. This provided a large dynamic range in radiometric and polarimetric values. We find that the Degree of Linear Polarization (DoLP) measured by both instruments agrees well with a RMS differences of ~0.005 as the best result for 555nm. For radiance measurements excellent agreement is obtained with a RMS difference of ~4%. The in-flight comparison results provide verification of SPEX airborne’s capability to deliver high-quality data.
Integration and testing of an imaging spectrometer for earth observation
Author(s):
Thomas Peschel;
Matthias Beier;
Christoph Damm;
Johannes Hartung;
Robert Jende;
Sandra Müller;
Mathias Rohde;
Andreas Gebhardt;
Stefan Risse;
Ingo Walter;
Ilse Sebastian;
David Krutz
Show Abstract
The DLR Earth Sensing Imaging Spectrometer (DESIS) is a space-based hyperspectral instrument developed by Deutsches Zentrum für Luft- und Raumfahrt (DLR). The optical system of the spectrometer was fabricated and prealigned by the Fraunhofer-Institut für Angewandte Optik und Feinmechanik (IOF).
The paper describes the manufacturing, integration, and testing of this optical system. It was realized as an all reflective system using metal-based mirrors and a modular, so-called snap-together approach, which allows to simplify the integration of optical systems considerably. Measured r.m.s. wavefront errors of the complete system are in the range of 63 nm to 120 nm, which is compliant with the instrument’s requirements.
Freeform optics design, fabrication and testing technologies for Space applications
Author(s):
Roland Geyl;
Eric Ruch;
Remi Bourgois;
Renaud Mercier-Ythier;
Hervé Leplan;
Francois Riguet
Show Abstract
The introduction of freefrom optical surfaces in a space instrument offers the possibility to improve its performance, its volume and weight or a combination of both. This is shown to be valid for either imaging systems or spectroscopic systems. At Safran Reosc we master freeform robotic polishing technology since more than 25 years and we will show how we continue to improve it in term of quality, productivity and adequacy to ceramic materials like Silicon Carbide. Surprisingly, the conservative space industry evolved slowly from spherical to rotationnally symmetric aspherical and off-axis optics during the last decades. This is no more valid today and we are proud to contribute to MicroCarb and IASI NG, two recent innovative projects taking benefit of such freeform optics designs enabling more cost-effective advanced missions. These projects will be briefly presented with their status of progess of work at the company. We will also take this opportunity to present our work on the extreme off-axis optics used within the MERLIN lidar project, produced with the same freeform technology.
Development of a low cost space telescope for Earth remote sensing from a 12U CubeSat
Author(s):
Helcio Vieira Jr.;
Manoel N. D. Barcelos Jr.
Show Abstract
The purpose of this work is to develop a low-cost space telescope for Earth remote sensing that could be housed in a 12U CubeSat with a GSD of 25 meters at LWIR. It will be used the Three Mirror Anastigmatic concept and Commercial Off- The-Shelf components whenever it is possible.
The telescope main mission is the oil spill detection, mainly in ocean environment. Beyond the obvious functionality of this main mission, the oil spill detection can be very useful to detect crashed aircrafts in the ocean.
As secondary missions, this telescope can be used to map deforestation, finding lost ships in the ocean and help the drug smuggling by finding camouflaged man-made objects.
The Project current stage consists in preliminaries optical and mechanical projects in which the mirrors follow ITAR regulation.
The telescope will operate in LWIR frequencies and will extract polarization information from the target.
The preliminary optical project indicates that the telescope optical performance has Modulation Transfer Function greater than 45% at Nyquist frequency, native GSD of 25 meters and that the telescope is diffraction limited (wavefront error of 0.012 wavelengths and Strehl ratio of 99.38%).
The preliminary mechanical project indicates that the maximum deflection caused by gravity induces to a despicable error (smaller than one over one hundred and forty) when compared to the mean wavelength of operation.
The preliminary radiometric analyses indicates that the telescope has a NETD of 0.90 K.
Design of all-reflective space-borne 1-m aperture solar optical telescope
Author(s):
Y. Suematsu;
H. Hara;
Y. Katsukawa;
R. Kano;
T. Shimizu;
K. Ichimoto
Show Abstract
A 1-m aperture optical telescope is planned for a future Japanese solar mission. The telescope is designed to provide high spatial resolution data of solar lower atmosphere from the photosphere to the uppermost chromosphere with enhanced spectroscopic and spectro-polarimetric capabilities covering a wide wavelength region from UV to near IR where many useful spectral lines and continua exist for physical diagnosis of the solar magnetized atmosphere. We designed an allreflective telescope to fulfill the scientific and engineering requirements. From a thermal view point, a Gregorian telescope is the most suitable. To avoid chromatic aberration, a tri-aspheric-mirror collimator coupling to the Gregorian was designed to give a diffraction-limited performance over the FOV by allowing a field curvature. The field curvature can be compensated by an off-axis Ritchey Chretien reimaging optics at an entrance of focal plane instrument, which has an opposite sign in the field curvature to the Gregorian. We also briefly studied structural design of all-reflective 1-m aperture solar optical telescope for the space solar mission.
Design and manufacture of 1.3 meter large caliber light-weighted Space optical components
Author(s):
Xiaoyong Wang;
Chongling Guo;
Yong Liu;
Jiayi Chen;
Yonggang Wang;
Yongli Hu
Show Abstract
The large-caliber light-weight reflector assembly is the core optical component of the large-size space camera. It needs to be highly light-weight to meet the constraint of emission weight. At the same time, the on-orbit reflector assembly needs to have extremely high force and thermal stability, be able to withstand the changes in the in-orbit temperature environment and the resulting stress changes and maintain the profile quality. This paper introduces the development of 1.3m caliber space mirror module. The reflector adopts the uniform thickness back arc design and the positioning support adopts the six-bar Bipod support technology. The simulation analysis verifies that the reflector component has good force and heat stability. The optical axis vertical test is carried out on the surface of the reflector assembly which has been processed and adjusted. The test results are consistent with the mechanical analysis results of the reflector assembly under the condition of gravity field, which meets the technical requirements of the spatial reflector.
Compact and Transportable Iodine Frequency-stabilized laser
Author(s):
J. Barbarat;
J. Gillot;
H. Alvarez-Martinez;
M. Lours;
D. Holleville;
R. Le Targat;
P. -E. Pottie;
P. Wolf;
P. Tuckey;
O. Acef;
F.-X. Esnault;
Thomas Leveque
Show Abstract
We report on a compact optical frequency standard (OFS) based on a Telecom laser diode operating at ~ 1542 nm, frequency stabilized to a narrow iodine transition located in the green range of the visible domain (~514 nm), after a highly efficient frequency tripling process. We use two cascaded waveguide Lithium Niobate nonlinear crystals for the third harmonic generation process (THG), resulting in a harmonic power of 300 mW in the green range (@3ω) using 800 mW of infrared power (@ω ). This result corresponds to an optical conversion efficiency Pω/Pω 36 % which is -to our knowledge- the best result ever reported for a third harmonic process in continuous wave regime (CW). This process uses only 20 W of total consumption power, which can be drastically reduced, knowing that less than 10% of that green power level is needed for the iodine Doppler free spectroscopy, and consequently for the frequency stabilization purpose. We have already demonstrated a frequency stability of 2.9 x10
-14 τ
-1/2 conferred to a laser diode operating at ~ 1542 nm, using the a1 hyperfine component of the R34 [44-0] located at ~ 514 nm. This corresponds to an amplitude spectral density of the residual frequency fluctuations < 10 Hz/√Hz.
We plan to extend this approach to set up a new OFS by using a narrow linewidth fiber-laser emitting at ~1597 nm, which will be used for the phase-locking of a 1064 nm laser. Thus, this OFS, compact and mainly fibered, will perform the same role as that of a rigid optical cavity, widely used to stabilize 1064 nm lasers, involved in various terrestrial applications or space missions. The compact design of the whole setup will make it easily transportable to different sites and could be readily used as an ultra-stable frequency reference.
2.0 micron wavelength injection seed semiconductor laser for lidar transmitter for global-scale measurements of CO2
Author(s):
Siamak Forouhar;
Ryan Briggs;
Mahmood Bagheri;
Clifford Frez;
Mathieu Fradet
Show Abstract
Many of the high accuracy Earth science survey missions are planned to use laser-based remote sensing instruments. The 2-μm laser wavelength is of particular interest due to the presence of many CO2 and H20 absorption lines in its vicinity1. Transmitter architectures are typically composed of an optically pumped, frequency-stable, solid-state seed laser and a high-power optical amplifier.2, 3 Taking advantage of the reliability and relative simplicity of semiconductor lasers, this architecture can substantially improve by replacing the solid-state light source with semiconductor lasers of comparable performance. This approach will greatly improve the system reliability, and will simplify instrument integration and space qualification. There are currently very limited semiconductor lasers operating in the 2-μm range with performance satisfactory enough for use as an injection seed in a laser absorption spectrometer. Optimally, seed lasers producing greater than 50 mW of continuous-wave (CW), with frequency jitter of less than 1 MHz are desired to reliably resolve the CO2 absorption lines near 2-μm. In this paper, we report the demonstration of high-power, single-longitudinal-mode laterally coupled distributed feedback (LC-DFB) lasers at 2.05 μm wavelength. We measured more than 80 mW of CW power at -10 ºC for devices with a 4-μm-wide ridge and 2-mm-long cavity.
Stable and high power 515-nm lasers for the space gravitational wave detector: DECIGO
Author(s):
Aru Suemasa;
Ayumi Shimo-oku;
Shunsuke Ohtsuka;
Masaki Nakamori;
Mitsuru Musha
Show Abstract
We have developed the frequency-stabilized lasers for gravitational wave detector DECIGO, whose short-term and long-term frequency stability is required to be df/f=10-15 level with the high output power of 10 W. The short- and long-term frequency stability is realized by using frequency reference of an iodine absorption signal at 515 nm. We made two Breadboard models to evaluate the frequency stability of the laser. The short-term frequency stability is improved to 30 Hz/√Hz at 1 Hz by suppressing the intensity noise of the laser at modulation frequency of 200 kHz, and long-term frequency stability also improved by suppressing residual amplitude modulation (RAM). For increasing the output power with keeping its frequency stability, a 2-stage cascade fiber amplifier has been developed. In the current presentation, we report the status of our frequency stabilized lasers and the schematic of its higher power unit.
Correlated atom accelerometers for mapping the Earth gravity field from Space
Author(s):
T. Lévèque;
C. Fallet;
M. Mandea;
R. Biancale;
J. M. Lemoine;
S. Tardivel;
M. Delpech;
G. Ramillien;
J. Panet;
S. Bourgogne;
F. Pereira Dos Santos;
Ph. Bouyer
Show Abstract
The emergence of quantum technologies, including cold atom based accelerometers, offers an opportunity to improve the performances of space geodesy missions. In this context, CNES initiated an assessment study called GRICE (GRadiométrie à Interféromètres quantiques Corrélés pour l’Espace) in order to evaluate the impact of cold atom technologies to space geodesy and to the end users of the geodetic data. In this paper, we present a specific mission scenario for gravity field mapping based on a twin satellite concept. The mission uses a constellation of two satellites each equipped with a cold atom accelerometer. A laser link measures the distance between the two satellites and couples these two instruments in order to produce a correlated differential acceleration measurement. The main parameters, determining the performances of the payload, have been investigated. In addition, a preliminary study of mass, consumption and volume has been conducted to ensure the onboard feasibility of these instruments. A general study of the satellite architecture, including all the subsystems, has also been realized and is presented here.
Global quasi-real-time-services back to Europe: EDRS Global
Author(s):
Harald Hauschildt;
Nicolas le Gallou;
Silvia Mezzasoma;
Hermann Ludwig Moeller;
Josep Perdigues Armengol;
Michael Witting;
Jörg Herrmann;
Cesar Carmona
Show Abstract
The Public-Private-Partnership between ESA and Airbus Defense and Space (Germany) has created the European Data Relay System (EDRS), which is operational since 2016.
The joint teams are running the Phase B of the globalisation of the European Data Relay System (EDRS) with an addition to the programme called EDRS Global (former GlobeNet).
EDRS Global is planning to increase the capacity of EDRS by adding a geostationary data relay payload, called EDRSD, over the Asia-Pacific region – in cooperation with Airbus DS partner JSAT (Japan). The heart of the system will be multiple laser terminals, based on TESATs upgraded design, featuring also a dual wavelength capability (1064 nm and 1550 nm) to serve more customers at the same time. The 1550 nm capabilities will be implemented in a cooperation between Airbus and TESAT (Germany), and NEC (Japan).
The evolution of the service will also aim for security sensitive user missions, including RPAS missions. The Laser Communication Technology on-board EDRS-D will be the starting point for the world’s first global laser based network in space, providing Global Secure Quasi-Real- Time-Services at Gigabit per second speed back to Europe by connecting its EDRS GEO nodes (EDRS-A/-C and EDRS-D) over 80,000 km distance by the means of optical communication.
The paper will provide details of the project and information about the latest status.
The CubeSat Laser Infrared CrosslinK Mission (CLICK)
Author(s):
Kerri Cahoy;
Peter Grenfell;
Angela Crews;
Michael Long;
Paul Serra;
Anh Nguyen;
Riley Fitzgerald;
Christian Haughwout;
Rodrigo Diez;
Alexa Aguilar;
John Conklin;
Cadence Payne;
Joseph Kusters;
Chloe Sackier;
Mia LaRocca;
Laura Yenchesky
Show Abstract
The CubeSat Laser Infrared CrosslinK mission is a joint Massachusetts Institute of Technology (MIT), University of Florida (UF), and NASA Ames Research Center effort to develop laser communications (lasercom) transceivers. The terminals demonstrate full-duplex intersatellite communications and ranging capability using commercial components to enable future large constellations or swarms of nanosatellites as coordinated distributed sensor systems.
CLICK will demonstrate a crosslink between two CubeSats that each host a < 2U lasercom payload. Range control is achieved using differential drag in Low Earth Orbit (LEO), with attitude controlled using a three-axis reaction wheel assembly and attitude sensors, including star trackers.
The lasercom terminals are direct-detect and rate scalable, designed to achieve a 20 Mbps crosslink at ranges from 25 km to 580 km and operate full-duplex at 1537 nm and 1563 nm with 200 mW of transmit power and a 14.6 arcscecond (0.07 milliradian) full width half max (FWHM) beamwidth. The terminals also use a 976 nm, 500 mW, 0.75 degree FWHM beacon and a quadcell for initial acquisition, and a low-rate radio crosslink for exchanging orbit information.
The payload transmitter is a master oscillator power amplifier (MOPA) with fiber Bragg grating for pulse shaping and MEMS fast steering mirror (FSM) for fine pointing, modeled after the MIT Nanosatellite Optical Downlink Experiment. The transceiver leverages UF’s Miniature Optical Communications Transmitter (MOCT) including a chip-scale atomic clock (CSAC). The receiver implements both a time to digital converter (TDC) as well as pulse recovery and matched filtering for precision ranging.
Optical intersatellite links for navigation constellations
Author(s):
Herwig Zech;
Philipp Biller;
Frank Heine;
Matthias Motzigemba
Show Abstract
Satellite constellations are used for navigation purposes since long. Connecting the satellites in a constellation by intersatellite links (ISLs) offers a full range of new possibilities. Ranging and time synchronization information can be exchanged between the satellites to improve the in orbit SC positioning knowledge. Besides ranging and time synchronization, ISLs can be used for service channel purposes or to distribute SW updates for the spacecrafts in a short period of time. ISLs improve the navigation constellations autonomy properties being less vulnerable to ground station unavailabilities.
For ISLs, radio frequency (RF) and optical technologies have been investigated. Due to the shorter wavelength, a better ranging resolution can be achieved with optical than with RF ISL solutions. Optical ISLs (OISLs) offer a very attractive solution for intersatellite links in terms of size, weight and power while providing multi gigabit per second data rate capabilities. In addition, optical communication links offer high operational security and immunity to interference sources while benefitting from a non-regulated optical frequency spectrum. For those reasons, optical intersatellite links for navigation constellations have been investigated in several studies supported by DLR and ESA. TESAT with partners have investigated the benefit of OISLs for navigation systems and on the Galileo OISL Terminal design.
In this paper, the results of these studies will be presented. Various OISL connection schemes in a navigation constellation are compared. The key design parameters of a Laser Communication Terminal for navigation systems will be given. Furthermore, the results of a lab demonstration showing the parallel distribution of ranging and communication data will be summarized. The focus of the investigation is on the Galileo navigation constellation.
1550-nm combined transmission booster amplifier and receiver preamplifier for satellite to satellite laser communication
Author(s):
François Gonthier;
Viorel Poenariu;
Jian Chu;
Dmitri Snejko;
Jonathan Lavoie;
Piotr Murzionak;
Emile Haddad
Show Abstract
Satellite-to-satellite laser communication technology underpins high-speed l0-Gbps optical links for the new generation of satellite constellations that will serve as global telecommunications networks. LEO satellite-to-satellite links may extend over distances of >5000 km, necessitating an optical-power budget of ~70 dB to compensate for diffraction-limited opticalbeam divergence. This can be achieved by boosting the transmitted laser diode signal to around 1 W, and by amplifying the received signal by 40 dB. Such performances are attained by terrestrial fiber amplifiers, operating in the telecom 1550- nm wavelength window, which are produced in volume of thousands and are (in relative terms) of low cost. Based on MPBC’s large volume production experience of fiber amplifiers and its heritage of space system design and manufacturing, a new product line of Laser Communication Terminals (LCTs) for space is presented. It is designed to be lower cost, exploiting commercial off-the-shelf (COTS) components whenever possible. Most of these fiber-optic components are extensively employed in large terrestrial telecom equipment and are already qualified to telecommunications standards. However, additional tests are required to ensure reliable long-term operation in a space environment. We have subjected the components, both active and passive, to gamma- and proton-radiation tests including total ionization doses of up to 100 kRad, Temperature vacuum cycling over extended temperature range have been performed and are still ongoing. Finally, considering manufacturing costs, we are packaging both the transmission optical booster unit and receiver optical amplification unit in the same housing, in order to co-locate both the transmit and receive functions of the link. These units are compact and stackable and save on the enclosure weight.
An all-silicon, high precision double-slit device for hyperspectral imager EnMAP
Author(s):
G. Huber;
B. Sang;
M. Erhard;
G. Staton;
H. -P. Honold;
Stefan Schmitt;
Christoph Zauner;
Manuela Sornig;
Sebastian Fischer
Show Abstract
Modern space-born spectrometer applications more and more rely on highest-precision slit devices defining the spectrometer entrance aperture. Reason for this is the increasing demand for broadband and high-resolving spectrometer or imaging spectrometer applications. High-NA optics necessitate very thin (microns) and accurate slit structures, whose manufacturing is demanding or impossible with common technology. In addition, they must withstand harsh environmental loads like shock, vibration and thermal cycling.
The hyperspectral imager of the Environmental Mapping and Analysis Program (EnMAP) satellite mission comprises two spectrometers whose entrance slits are realized by an all-silicon, highly integrated double slit device. It is manufactured by use of micro-machining and lithographic processes, reaching sub-micron geometric precision. Each slit aperture is 24 μm x 24 mm large, corresponding to an aspect ratio of 1:1000. In some critical respects – such as planarity or coalignment – the technology excells established manufacturing technologies like metal electroforming, milling and others.
In addition to slit aperture definition, the double slit device achieves field separation for the two imaging spectrometers. One of the two transmitted light beams is deflected by a flat mirror. The minute silicon mirror is completely integrated into the device. The EnMAP slit assembly has undergone an intensive qualification test program. Included were vibrational, shock and thermal load tests as well as a more specific sun intrusion test. The results of these tests are briefly presented and discussed.
Slit homogenizers for Earth observation spectrometers: overview on performance, present and future designs
Author(s):
Jérôme Caron;
Bob Kruizinga;
Rob Vink
Show Abstract
Tropomi, successfully launched in October 2017, and Sentinel-5, with launch due in 2021, are two pushbroom spectrometers measuring Earth’s radiance from a Low Earth Orbit (LEO) at a high spectral resolution. Both instruments have strongly overlapping spectral channels (UV-VIS, NIR, SWIR-3). While the Tropomi spectrometers are designed with standard slits, all Sentinel-5 channels make use of complex slit assemblies called “slit homogenizers” that aim at mitigating the slit heterogeneous illumination that results from the along track spatial non-uniformity of the observed scenes, and is known to distort the instrument spectral response function (ISRF). The similarity between the two missions will allow, in a few years from now, to evaluate the performance gain resulting from these devices. If their expected success is confirmed, slit homogenizers may become standard components of future space missions. This paper aims at providing a comprehensive, yet as simple and accessible as possible, overview of the slit homogenizer performance. The Sentinel-5 slit homogenizers, based on two parallel mirrors will be discussed, and a new and promising family of slit homogenizer designs will be presented for the first time. The new designs offer several advantages in terms of performance and manufacturability.
Optical performance of NISP grisms flight models for EUCLID mission
Author(s):
Anne Costille;
A. Caillat;
C. Rossin;
S. Pascal;
P. Sanchez;
B. Foulon;
C. Pariès;
S. Tisserand;
Y. Salaun;
T. Weber
Show Abstract
The launch of ESA EUCLID mission is foreseen in 36020. The goal of the mission is to understand the nature of the dark energy and to map the geometry of the dark matter. The EUCLID telescope will be equipped with two instruments working in the visible range (VIS) and in the IR range (NISP) to investigate the distance-redshift relationship and the evolution of cosmic structures. The NISP (Near Infrared Spectro-Photometer) will operate in the near-IR spectral range (0.9-2μm) with two observing modes: the photometric mode for the acquisition of images with broadband filters, and the spectroscopic mode for the acquisition of slitless dispersed images on the detectors. NISP is then using four low resolution grisms to acquire spectroscopic image in different orientations to better distinguish the spectra observed and to cover two spectral ranges: 1250-1850nm range, and 920-1300nm range. Since 2010, Laboratoire d’Astrophysique de Marseille is working on the development and the test of the NISP grisms, that are complex optical components. The grism combines four main optical functions: a grism function done by the grating on the prism hypotenuse, a spectral filter done by a multilayer filter deposited on the first face of the prism, a focus function done by the curved filter face of the prism and a spectral wavefront correction done by the grating which grooves paths are nor parallel, neither straight. The NISP instrument is now entering in the integration phase of the proto flight model of the instrument. Therefore, the NISP grism flight models have been manufactured and delivered to the grism wheel assembly for integration by end of 2017. In this paper, we present the optical performance and characteristics of the four EUCLID NISP grisms flight models that have been developed and manufactured by four different industrial partners then integrated and tested by LAM. We focus on the performance obtained on the optical performance of the component; wavefront error of the components, the spectral transmission and groove profiles. The test results analysis show that the grisms flight models for NISP are well within specifications with an efficiency better than 70% on the spectral bandpass and a wavefront error on surfaces better than 30nm RMS. The results on the component show a good control of the manufacturing and integration process despite the difficulties at the beginning of the project to manufacture these components.
All-dielectric prism-grating-prism component realized by direct hydrophilic bonding technology for optical applications in space
Author(s):
Thomas Flügel-Paul;
Carolin Rothhardt;
Tino Benkenstein;
Kevin Grabowski;
Stefan Risse;
Ramona Eberhardt;
Benedikt Guldimann;
Uwe D. Zeitner
Show Abstract
Here, we report on the approach of realizing an all-fused-silica PGP disperser (prism + grating + prism) by low temperature direct bonding. A surface relief grating with period 660nm and overall depth of approximately 2000nm is sandwiched between two equal prisms. Direct bonding of glass relies on the formation of covalent bonds between hydrophilic silicon-oxide surfaces. Compared to other joining technologies, like adhesive bonding or optical contacting, the established connection is stiff, shows no outgassing, is highly resistant against chemical and radiative degradation and the established optical interface is intrinsically impedance-matched. In summary, two prototypes were realized, optically characterized and successfully underwent environmental testing. The overall diffraction efficiency of the PGP is larger than 90%.
Additive manufacturing of an AlSi40 mirror coated with electroless nickel for cryogenic space applications
Author(s):
Sebastian Eberle;
Arnd Reutlinger;
Bailey Curzadd;
Michael Mueller;
Mirko Riede;
Christoph Wilsnack;
Ana Brandão;
Laurent Pambaguian;
André Seidel;
Elena López;
Frank Brueckner;
Eckhard Beyer;
Christoph Leyens
Show Abstract
Advanced Manufacturing (AM) has the potential to improve existing technologies and applications in terms of performance, light-weighting and costs. In the context of the SME4ALM initiative, launched by DLR and ESA, the company Kampf Telescope Optics GmbH (KTO) in cooperation with the Fraunhofer Institute for Material and Beam Technology (IWS) have assessed the feasibility of AM to build a high-performance optical mirror for space applications.
For the assessment of the AM potentials, a mirror design concept for cryogenic instruments for observations in the IR and NIR range was baselined. In a second step, Nickel-Phosphorus (NiP) was selected as optical coating. The combination of coating and mirror material is a primary design driver for optical performance. Both materials must have a very similar CTE as well as be compliant to modern optical manufacturing (diamond turning, polishing). As a promising candidate for NiP coating the AlSi40 was selected for the mirror structure.
The potential advantages of AM for optical mirrors in terms of mechanical performance, cost, and manufacturing time were exploited. The achievement of those objectives was / will be demonstrated by:
1. verifying AM material properties and manufacturability of AM mirrors by material sample tests and subcomponent tests
2. designing AM mirror demonstrator by structural, thermal, and optical performance analysis
3. applying and elaborating AM specific design methods (topology optimization, sandwich structures with internal microstructures, monolithic design, etc.)
4. manufacturing, assembling, and testing AM mirror demonstrator to verify manufacturability and optical performance
5. comparing optical and mechanical performance of the AM mirror demonstrator to a conventional mirror by numerical analysis to exploit potential advantages of AM
Manufacturing of thin glass shells for future space telescopes
Author(s):
G. Vecchi;
S. Basso;
M. Civitani;
M. Ghigo;
G. Pareschi;
B. Salmaso
Show Abstract
We present a method for the manufacturing of thin shells of glass, which appears promising for the production of lightweight mirrors for future space telescopes. The method exploits the synergy of different mature technologies, while it takes advantage of the commercial availability of large, high-quality sheets of glass, with thickness up to few millimeters. The first step of the method foresees the pre-shaping of flat substrates of glass by replicating the accurate shape of a mold via hot slumping technology. The replication concept can be strongly beneficial for making large optics composed of many identical or similar segments. After the hot slumping, the shape error residual on the optical surface is addressed by applying a deterministic sub-aperture technology as computer-controlled bonnet polishing and/or ion beam figuring. Here we focus on the bonnet polishing case, during which the thin, deformable substrate of glass is temporary stiffened by a removable holder. In this paper, we report on the latest results achieved on a 130 mm glass shell case study.
ZERODUR as a dimensionally stable mirror substrate material for spaceborne telescopes
Author(s):
Tony Hull;
Antoine Carre;
Ralf Jedamzik
Show Abstract
Demanding new environmental requirements for earth observation, and for astrophysics, may impose ultrastability requirements on telescope mirrors. Dimensional stability of the mirror material under environmental boundary conditions is as important to the success of a mission, if not more so, than considerations of strength and stiffness. Among these characteristics is the response of the mirror material to variable thermal stimulus. It is found that not only the mirror material’s coefficient of thermal expansion (CTE) is important, but also the homogeneity of the material characteristics. Furthermore the match of thermal characteristics between the mirror material and those of metering structure contributes to maintaining a manageable error budget for operations under various view factors to sun and earth.
Metal mirror based VIS freeform telescope with smart integration approach
Author(s):
Matthias Beier;
Stefan Risse;
Wolfgang Holota;
Christoph Straif;
Sebastian Fischer
Show Abstract
Modern optical telescopes for Earth observation and remote sensing operations often rely on off-axis mirror designs with aspheric or free-shaped surfaces in order to generate an unobscured image while at the same time covering a large field of view and maintaining an excellent system quality. Continuous improvements in manufacturing and test methods allow for the fabrication of freeform surfaces with low tolerances on figure and roughness. We describe the development, fabrication, and testing of an anamorphic imaging four mirror freeform telescope that operates diffraction limited at visible wavelengths. Based on fabrication and test techniques developed, figure errors of each optical freeform surface were reduced to < 12 nm rms. Roughness values < 0,5 nm rms have been realized based on the applied polishing processes. The optomechanical design of the telescope aims at a minimum of integration effort, reducing the relevant degrees of freedom during mirror alignment from 24 to 3 only and thus allowing for a total system integration within one single day. The telescope concept ensures a reproducible integration and therefore allows for a multi-stage integration after different manufacturing steps in order to correlate surface errors of different spatial frequency with observed wave aberrations on system level. The final experimentally obtained wave aberration is in excellent agreement to the optical design.
Space- and ground-based non-accelerated long lifetime data for ruggedized commercial NPRO lasers
Author(s):
C. G. Asbury;
L. I. Dorsky;
N. M. Nerheim;
S. Forouhar;
D. M. Rider;
E. Y. Chu;
B. M. Fisher;
R. S. Valencia;
M. R. Montero;
T. J. Kane
Show Abstract
Lifetime data is presented for ruggedized commercial NPRO lasers used in the Tropospheric Emission Spectrometer (TES) Instrument on NASA’s Aura Earth-orbiting spacecraft, including 20 years of data from two life test units on the ground, 12 years of on-orbit data from TES Laser A, and 2 years of on-orbit data from TES Laser B. The TES lasers are diode-pumped Non-Planar Ring Oscillator (NPRO) lasers using Nd:YAG crystals. Since accelerated life testing was not possible on the complete laser, early prototype lasers that had gone through thermal cycling and vibration testing were placed on non-accelerated life tests with the hope of gathering at least a couple of years of data before launch. Long-term lifetime data for hybrid laser systems in space applications is not abundant, and out of necessity, accelerated reliability testing is usually done over a relatively short time with a large number of devices. The data presented in this paper is unique as it tracks the optical power output over time of a total of four lasers on the order of decades rather than months or years. Two of the lasers have each been on life test for over 20 years on the ground and are still operating, and the other two lasers have been on-orbit for 14 years. TES Laser A was still operating when the TES Instrument was decommissioned in January 2018. Therefore, the data presented covers over 450,000 non-accelerated device-hours, with 23% of those hours being in space.
Laser source electronics (LASE) for the infrared atmospheric sounder interferometer next generation (IASI-NG)
Author(s):
Lars Lierstuen;
Sedsel F. Thomassen;
Eystein T. Saether;
Steinar Johnsen;
Benjamin Hagaas;
Cathrine Brecht;
Rune Raknerud;
Yngve Lien;
Ivar Miljeteig;
Even Frøen;
Terrence Lockey
Show Abstract
The MetOp-SG satellite program is an EUMETSAT/-ESA cooperation with the objective to obtain long-term collection of remotely sensed data of uniform quality for meteorology and climate monitoring state analysis and forecast. A series of three satellite pairs (MetOp-SG-A1, -A2 and –A3) are to be launched, ensuring continuity of data to beyond 2045.
The Infrared Atmospheric Sounder Interferometer Next Generation (IASI-NG), being developed by CNES, is one of the instruments on the MetOp-SG-A’s. The IASI-NG is a Fourier Transform Infrared Spectrometer scanning the atmosphere to provide data for atmospheric gas characterisation.
Kongsberg Defence and Aerospace (KDA) has developed the LAser Source Electronics (LASE) for the IASI-NG instrument. The LASE provides a wavelength-stabilized optical source to be injected into the IASI-NG with a wavelength stability within ± 0.00015 nm throughout the instrument lifetime. The wavelength is locked and controlled using a feedback-loop containing a gas cell filled with
13C
2H
2. The LASE shall in addition perform the conversion of the optical signal from the interferometer into analogue electrical signal which can be further processed. The lifetime includes 15.75 years of storage and 7.75 years in space.
The challenge of meeting the required Polarisation Extinction Ratio (PER) for a fiber optical system, as the one in LASE, is discussed.
UV-DPSS laser flight model for the MOMA instrument of the ExoMars 2020 Mission
Author(s):
Peter Weßels;
A. Büttner;
M. Ernst;
M. Hunnekuhl;
R. Kalms;
L. Willemsen;
D. Kracht;
J. Neumann
Show Abstract
The flight model of the laser system for the Mars Organic Molecule Analyzer (MOMA) instrument within the ExoMars 2020 mission for Martian planetary surface exploration has been developed, assembled, tested, and finally integrated to the NASA Goddard Space Flight Center (GSFC) mass spectrometer. The nanosecond laser system consists of a longitudinally pumped, passively Q-switched Nd:YAG based laser oscillator with a two-stage frequency doubling to 266 nm. The laser design was implemented in robust and lightweight models of the laser head (LH) with the pump unit in a separate electronics box.
In parallel to the laser head integration and testing, materials and optics qualification and acceptance tests have been performed, e.g. to determine the optical damage threshold or the susceptibility to laser induced contamination processes.
Before delivery to the NASA GSFC for integration to the mass spectrometer (MS) flight model (FM), the laser system has been qualified in an environmental test campaign including vibration, shock and thermal-vacuum testing. After delivery to GSFC and integration to the FM MS, the system has been successfully re-tested on the instrument level.
Highly efficient mJ level laser amplifiers at 2 microns for frequency comb spectroscopy
Author(s):
Sébastien Vidal;
Alain Jolly;
Philippe J. Hébert;
Benoit Faure;
Johan Boullet
Show Abstract
Over the last decade, frequency comb spectroscopy have led to significant developments in view of the identification of varied species and of the understanding of the structure of matter.
Highly efficient amplification of frequency comb femtosecond oscillators in the high pulse energies regime should allow future applications using this approach to Lidar-type measurements.
We report on the millijoule level design of femtosecond amplifiers near 2 μm wavelength having a great optical efficiency and compactness in order to be carrier in satellites. In addition to space applications, laser systems at 2 μm become more and more popular because they offer elegant solutions to generate ultra-broad band super-continuum in the mid-infrared and for material processing.
Our study helps to compare the optical performance of Tm:YAG, Tm:YAP and Tm:YLF crystals as active media, for designing ultrashort pulse regenerative amplifiers with a high gain and wall-plug efficiencies up to 10%. We will present our approach to ensure the conservation of the initial phase shift between the envelope and the carrier of pulses during amplification.
We primarily discuss an innovative model which proposes a gradual path towards the optimization of any regenerative amplifier using crystalline thulium-based, end-pumped doped rods. This also involves the analysis of sizing criteria based on the assumption of rod-based active media, including the doping content, the length of the rod and the beam size inside.
Three years of optical satellite to ground links with the T-AOGS: data transmission and characterization of atmospheric conditions
Author(s):
K. Saucke;
R. Mahn;
P. Martin Pimentel;
F. Heine;
R. Mata-Calvo;
J. Surof;
Ricardo Barrios;
A. Reeves;
H. Bischl;
H. Brandt;
B. Matuz
Show Abstract
After more than 3 years of operational experiences with the Transportable Adaptive Optical Ground Station (T-AOGS) it is not any more the question whether optical communication through atmosphere is possible for Geo to ground applications. It is important to understand the performance of optical communication under different atmospheric-conditions and which the key parameters are to improve simplicity, robustness and availability of optical bi-directional satellite to ground links (SGL). We report within this paper on the characterization of the atmospheric channel for ground to GEO optical communication without adaptive optics correction in the uplink. Besides the telemetry data of the space segment and the T-AOGS, also a special measurement campaign was carried out using the 1m telescope of the ESA-OGS in parallel. An outlook for further analysis and activities is given.
Demonstrated pre-compensation of a focused laser beam with up to 0.27 mrad point-ahead-angle over a 1-km horizontal communication path
Author(s):
A. Brady;
N. Leonhard;
C. Rößler;
M. Gier;
P. Böttner;
C. Reinlein
Show Abstract
In the development of laser communication networks, atmospheric turbulence remains an obstacle in the efficiency optimisation of bidirectional optical links. Post-compensation of the downlink signal through adaptive optics (AO) has been verified as a method of increasing the efficiency of satellite-to-ground optical links, however, similar efficiencies have yet to be achieved in the opposite direction (uplink) largely due to the shower curtain effect and the consequent impossibility of conducting post-compensation over the smaller receiver aperture at the satellite terminal. Pre-compensation is anticipated to be a promising method of increasing the efficiency in uplink communications for Earth-to- GEO optical feederlinks, by pre-distorting the uplink wavefront prior to propagation through the atmosphere using measurements of the downlink. Here, we present the recent modifications to our current experimental setup and initial results of a pre-compensation experiment conducted over a 1 km horizontal path. The experiment aimed to investigate pre-compensation under a point-ahead-angle for the special case of a focussed uplink beam. Two optical terminals were developed, a “ground terminal breadboard” (GTB) consisting of a commercially available 30 cm reflective telescope in combination with an AO-box [3] capable of simultaneous post-and pre-compensation and a “satellite terminal breadboard” (STB) with separate transmission and receiving apertures for measurement of the uplink beam under a point-ahead-angle (PAA). We present a first look at and discussion of the experimental results which show that AO pre-compensation increased the measured intensity of the uplink beam over the receiving aperture of the STB for a PAA of up to 0.27 mrad.
Impact of molecular absorption on the design of free space optical communications
Author(s):
G. Artaud;
B. Benammar;
D. Jouglet;
L. Canuet;
J. Lacan
Show Abstract
Free space optical communications systems have to deal with several impairments originating from the interaction of optical signals with the local environment and the atmosphere. These impairments include cloud blockage, aerosols scattering, molecules absorption and turbulence. In this paper, we focus on the impact of molecular absorption bands on the choice of uplink/downlink data wavelength division multiplexing grids (WDM) as well as uplink Pointing/Acquisition and Tracking (PAT) beacon wavelength.
Cloud free line of sight prediction modeling for low earth orbit optical satellite networks
Author(s):
Nikolaos K. Lyras;
Charilaos I. Kourogiorgas;
Athanasios D. Panagopoulos
Show Abstract
In this paper, a methodology for the generation of cloud free line of site time series for low earth orbit optical satellite communication systems is presented. The proposed methodology is based on the synthesis of 3D cloud fields employing Integrated Liquid Water Content (ILWC) statistics. The methodology captures the temporal and spatial variability of cloud coverage and takes into account the varying elevation angle of the LEO optical link with each optical ground station (OGS) and the altitude of each OGS for the estimation of the CFLOS probability. The ILWC statistical parameters required for the CFLOS time series are taken from ERA Interim data base, European Centre for Medium- Range Weather Forecasts (ECMWF). Finally CFLOS numerical results are reported and some significant conclusions are drawn.
Binary blazed reflection grating for UV/VIS/NIR/SWIR spectral range
Author(s):
Frank Burmeister;
Thomas Flügel-Paul;
Uwe D. Zeitner;
Mane-Si-Laure Lee Bouhours;
Gaëlle Lehoucq;
Julie Cholet;
Brigitte Loiseaux;
Nicolas Tetaz;
Roman Windpassinger;
Matteo Taccola
Show Abstract
We report on the design and fabrication of a reflection grating for hyperspectral applications operating in the range from 340 nm to 1040 nm wavelength. The blazed grating is based on an effective medium approach, where the desired functionality is realized using a binary surface relief structure. For each period, a gradient in size of the local grating features mimics an interface which adds a linear phase profile to the illuminating beam – thus introducing diffraction. The surface relief structure is composed of 2D structures - pillars with diameters from 200 nm to 350 nm to voids with diameters from 300nm to 120 nm. Overall, an entire number of ~50 such features are arranged to establish an overall unit cell of the grating over a length of 30 μm. By purposeful design of size, shape and arrangement of the sub-wavelength features such gratings offer novel opportunities in tailoring the spectral response, i.e. particular broadband efficiency or the enhancement of the efficiency in specific sub-domains of the spectrum. We will present measured performance results of a grating covering a circular area of 80mm in diameter manufactured on a 4inch-wafer. Finally, we will give an outlook on how such structures can be applied to curved surfaces and even ultra-broadband operation.
Tailored dispersive elements for adapted spectrometric sensing
Author(s):
Torsten Diehl;
Peter Triebel;
Tobias Moeller;
Alexandre Gatto;
Dennis Lehr;
Alexander Pesch;
Lars H. Erdmann;
Matthias Burkhardt;
Alexander Kalies;
Felix Koch
Show Abstract
Dispersive elements are in general the key components of spectrometers and define mainly their performance. Prisms and filters are typically used for lower resolution applications, e.g. color measurement for industrial applications. Many high performance spectrometer applications are using gratings as dispersive elements instead. Different spectrometer layouts require various grating approaches in order to maintain the optical imaging performance. A frequent aim is a progressively optimization of the optical performance in balance to the mechanical parameters like weight, volume or robustness against variations of environmental conditions of a spectrometer module as well. Thus, the optical designer has to draw on additional design degrees of freedom. This in turn results often in more and more complex grating types featuring curved substrates and/or variable and bended grating lines. Especially the trend toward hyperspectral imaging applications demands appropriate options for enhanced field correction. The main ZEISS technology chain for grating manufacturing includes holography and reactive ion etching is a flexible base for these special types of gratings. A close entanglement between holography and accurate test procedures for the optical functionality of the holographic grating is a pre-condition for the ability to meet the often challenging specifications. Therefore, beside the brief description of the manufacturing technology in this text we show a set of newly developed measuring procedures supporting the holographic surface patterning approach.
Manufacturing and optical performance of silicon immersed gratings for Sentinel-5
Author(s):
Ralf Kohlhaas;
Paul Tol;
Ruud Schuurhof;
Robert Huisman;
Stephen J. C. Yates;
Geert Keizer;
René Wanders;
Sander van Loon;
Tonny Coppens;
Mustafa Kaykisiz;
Phillip Laubert;
Peter Paul Kooijman;
Aaldert van Amerongen;
Luc Dubbeldam
Show Abstract
In this article the immersed gratings for the ESA Copernicus Sentinel-5 mission are presented. The manufacturing approach is shown and the optical performance of the SWIR-3 immersed gratings as well as the results of the environmental tests are discussed. The immersed gratings show an average efficiency of 60% and a wavefront error of 200 nm rms. The total integrated scatter over the complete stray-light hemisphere excluding ghosts from internal reflections is found to be 0.2% using a conservative estimate. A method for the derivation of the wavefront error from separate surface measurements is presented and the results are compared to measurements with an experimental Shack- Hartmann setup. The immersed gratings are produced by bonding a prism to a wafer with a grating. Environmental tests and testing at operational temperatures show the suitability of this approach for complex space optical components. The article concludes with possible improvements in the optical performance of future immersed gratings.
UV Ruled Grating for the Mars atmosphere and Volatile EvolutioN (MAVEN) mission
Author(s):
A. Cotel;
A. Liard;
F. Desserouer;
Y. Bernard;
P. Pichon
Show Abstract
NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) mission advances the understanding of planetary habitability and climate change by investigating how Mars lost its early atmosphere and abundant liquid water. We will present here the UV ruled master diffraction grating design, development and performances provided for the MAVEN mission. We will firstly focus introduce HORIBA Scientific capabilities and heritage for low groove density ruled blazed grating development. Then, we will introduce the grating design with the blazed profile and efficiency optimization and finally the performances characterization we obtained on the flight model gratings.
ATHENA Telescope: alignment and integration of SPO mirror modules
Author(s):
G. Valsecchi;
F. Marioni;
G. Bianucci;
F. E. Zocchi;
D. Gallieni;
G. Parodi;
M. Ottolini;
M. Collon;
G. Pareschi;
D. Spiga;
M. Bavdaz;
E. Wille;
V. Burwitz;
G. Hartner;
C. Pelliciari
Show Abstract
ATHENA (Advanced Telescope for High-ENergy Astrophysics) is the next high-energy astrophysical mission of the European Space Agency currently planned to be launched in the early 2030s, as part of its Cosmic Vision program, on the scientific topic of “Hot and Energetic Universe”. The optics technology is based on the Silicon Pore Optics (SPO). About 678 SPO mirror modules will have to be integrated and co-aligned onto the optical bench of the Mirror Assembly Module (MAM) of ATHENA. This activity will have to be completed in about two years. Media Lario leads an industrial and scientific team that has developed the process to align and integrate the SPO Mirror module with an accuracy better than 1 arcsec. The process is based on position of the centroid of the point spread function produced by each mirror module when illuminated by a collimated planewave at 218 nm taken at 12 m focal length. Experimental tests, using two SPO mirror modules, and correlation with X-ray measurement at the PANTER test facility in Münich have demonstrated that this process meets the accuracy requirement. It was also demonstrated, that a mirror module can be removed again from the MAM, and re-installed, without compromising the adjacent mirror modules. This technique allows arbitrary integration sequence and integration of two Mirror Modules per day. Moreover, it enables monitoring the telescope point spread function during the whole integration phase.
Optical alignment of the Solar Orbiter EUI flight instrument
Author(s):
A. Mazzoli;
J. -P. Halain;
F. Auchère;
J. Barbay;
S. Meining;
A. Philippon;
G. Morinaud;
S. Roose;
M. -L. Hellin;
L. Jacques;
U. Schühle;
C. Dumesnil;
R. Mercier;
E. Renotte;
P. Rochus
Show Abstract
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter mission will image the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). It is composed of three channels, each one containing a telescope.
Two of these channels are high resolution imagers (HRI) at respectively 17.1 nm (HRI-EUV) and 121.6 nm (HRI-Ly∝), each one composed of two off-axis aspherical mirrors. The third channel is a full sun imager (FSI) composed of one single off-axis aspherical mirror and working at 17.1 nm and 30.4 nm alternatively. This paper presents the optical alignment of each telescope.
The alignment process involved a set of Optical Ground Support Equipment (OGSE) such as theodolites, laser tracker, visible-light interferometer as well as a 3D Coordinates Measuring Machine (CMM).
The mirrors orientation have been measured with respect to reference alignment cubes using theodolites. Their positions with respect to reference pins on the instrument optical bench have been measured using the 3D CMM. The mirrors orientations and positions have been adjusted by shimming of the mirrors mount during the alignment process.
After this mechanical alignment, the quality of the wavefront has been checked by interferometric measurements, in an iterative process with the orientation and position adjustment to achieve the required image quality.
Full-SiC EUCLID's very large telescope
Author(s):
Michel Bougoin;
Florent Mallet;
Jérôme Lavenac;
Alexandre Gerbert-Gaillard;
Dirk Ballhause;
Frédéric Chaumeil
Show Abstract
Euclid is a part of the European Space Agency Cosmic Vision Medium Class program. This mission’s goal is to investigate the nature of dark energy, dark matter and gravity by observing the geometry of the Universe and the formation of structures over cosmological timescales.
Euclid Payload Module (PLM) includes a large three mirrors anastigmatic Korsch telescope feeding a visible imager (VIS) and a near-infrared spectrometer and photometer (NISP). The hardware of all of them will be mainly made of Boostec® SiC material.
The SiC telescope has been designed by Airbus Defence and Space team in Toulouse (France).
The PLM is divided in two cavities which are separated and hold by a very large SiC baseplate; the front one includes the primary and secondary mirrors and the associated support structure while the back one consists of the telescope folding mirrors, the tertiary mirror, the two instruments (VIS and NISP) and other optical devices. The focal length is 24.5 m and the useful pupil diameter is 1.2 m. A passive thermal concept has been developed, thus requiring minimum heating power and providing best thermal stability. The telescope will operate at ≈130 K.
In addition to its high thermal conductivity, the Boostec® SiC has been chosen for its mechanical properties and its ability to greatly reduce mass. The full SiC telescope architecture gives high optical stability.
The present paper describes the very large full-SiC telescope and the manufacturing process of its SiC parts, in particular the mirrors, the lightweight baseplate and the spider.
Development of the wide-swath and high-resolution optical imager onboard advanced optical satellite (ALOS-3)
Author(s):
Hidenori Watarai;
Haruyoshi Katayama;
Tomoya Niwa;
Masakazu Sagisaka
Show Abstract
JAXA has developed the Advanced Optical Satellite (ALOS-3) as a successor to the optical mission of the Advanced Land Observing Satellite (ALOS) "Daichi" (2006 - 2011) since FY 2016. The wide-swath and high-resolution optical imager (WISH) is the main instrument of ALOS-3 and equipped with a panchromatic (Pa) band and 6 multispectral (MS) bands. For the optics of WISH, a large off-axis four mirror anastigmat type has been selected to achieve both highresolution (0.8 m Pa, 3.2 m MS) and wide-swath (70 km). The proto-flight model (PFM) of all mirrors has already in the precision polishing process, and highly accurate measurements of large off-axis aspherical surfaces (primary and tertiary mirror) are carried out both in a contact and a non-contact method. The verification concerning the high precision assembly of the large off-axis optical system was also carried out using the structural model which is manufactured with the same design for the PFM. Manufacture and test of the PFM of WISH would be conducted over the next one year and the PFM would be delivered to the ALOS-3 satellite system within FY 2019. ALOS-3 is scheduled to be launch from Tanegashima Space Center in FY 2020.
Aeolus first light: first glimpse
Author(s):
T. Kanitz;
J. Lochard;
J. Marshall;
P. McGoldrick;
O. Lecrenier;
P. Bravetti;
O. Reitebuch;
M. Rennie;
D. Wernham;
A. Elfving
Show Abstract
ESA deployed the first Doppler Wind lidar in space within its Earth Explorer Mission Aeolus. The objective of Aeolus is to provide tropospheric and lower stratospheric wind profiles globally for the improvement of weather forecasts on short and medium term. Spin-off products are profiles of atmospheric backscatter and extinctions coefficients and lidar ratio. The observations will also be used as input to air quality models and to verify climate model parameterization and predictability. After the successful launch in late August this year an intensive commissioning phase is taking place in the first three month of the mission, including the first switch on of the instrument ALADIN and its calibration in flight. First preliminary results will be presented during the talk.
ATLID, ESA atmospheric LIDAR: integration of instrument and tests
Author(s):
G. de Villele;
J. Pereira do Carmo;
A. Helière;
A. Lefebvre;
L. Barbaro;
T. Belhadj;
F. Chassat;
B. Corselle;
R. Evin;
M. Feral;
I. Levret;
P. Lingot;
F. Olivier;
S. Pelletier;
J. Pochet;
A. Schaube;
F. Varlet;
P. Vlimant
Show Abstract
The ATmospheric LIDar (Light Detection and Ranging), ATLID, is part of the payload of the Earth Cloud and Aerosol Explorer (EarthCARE) mission, the sixth Earth Explorer Mission of the European Space Agency (ESA) Living Planet Program. After the successful major step of optical and electrical integration, ATLID has started its performance and functional testing in Toulouse Airbus Defence and Space. The emission part of the instrument has been operated with both TxA (Laser transmitter units) delivered from Leonardo team: as major achievement the main performance of both flight lasers have been tested and confirmed with more than 40mJ UV emission @51Hz with operation via instrument control ACDM flight unit (ATLID control and data management). Tests are parallelized with on one side the EFM test (Electrical Flight Model), and on the other side the OFM tests (Optical flight model). The EFM tests aim at validating the functional and electrical architecture via functional testing on each nominal and redundant path with all the flight electronic units and laser sources. The OFM tests aims validating the receiver alignment from telescope input till fiber detectors, the field of view of the three detection channels and their radiometric performance. OFM vibration tests have been performed and have validated design stability against mechanical loads. End of OFM and EFM tests is planned at summer 2018 and will give go ahead for instrument assembly in its final ATLID PFM configuration with laser cooling system integration. After Ambient performance testing, the environmental test campaign immediately start with EMC, mechanical and thermal vacuum testing.
SCALE: validations and prospects for a novel type of sounding lidar using short frequency combs
Author(s):
Philippe J. Hébert;
François Lemaître
Show Abstract
As compared to near InfraRed passive instruments, lidars reduce the biases on the measurement of concentrations in the presence of diffusion by aerosols, but until recent days they were limited to one active wavelength at a time.
CNES and ONERA conceived a novel type of lidar based on short frequency combs that provides the spectrum of a complete absorption line of the target molecule. The technique of Dual Comb Spectroscopy is adapted to short (up to 13 teeth) combs, as a compromise between spectral richness and Signal to Noise Ratio. The advantages of DCS remain: reduction of the impact of scene evolutions and spectral mis-calibration. The latter will make the high power laser emitters easier. Above all, the acquisition of a complete absorption line opens the path to the retrieval of two or more independent elements in the vertical profile of molecule concentration.
We describe the technique of comb generation, the layout of the emitter section and the detection principles. Then we introduce the Short Comb Atmospheric Lidar Experiment (SCALE) project led by CNES in the frame of a new advance “phase 0” study. We expose the preliminary performances of this space lidar that could fit on a microsatellite platform in the case of CO
2 sounding at 1.57 or 2 μm.
Results of CNES-ONERA four-year R&T activities are also presented that validate in the laboratory and in open space the short comb lidar.
Finally first results of retrieval simulations are exposed.
LIDAR echo emulator
Author(s):
Pawel Adamiec;
Alvaro Machon;
Monica Rodriguez Cortina;
Alejandro Lopez Moya;
Enrique Cordero;
Juan Barbero
Show Abstract
The LIDAR Echo Emulator (LEE) emulates the returned signals from a Lidar system. As the return signal of a Lidar system depends on the target, this implies the capability of shaping the lasers returns. In brief, long echo corresponds to a natural or diffusive object (canopy, clouds) and short echoes to a hard object like roofs, ground, etc. Such signals are necessary to be simulated to study and validate new detectors and detection systems without developing/procuring entire Lidar system. LEE consists of pulse shaping electronics to drive independently the lasers for each echo and internal detection system to monitor the pulses. The short echoes can be in the range from 5 ns to hundreds of ns and the long echoes from 1 μs up to hundreds of μs. The repetition rates of the developed emulator are from 100 Hz to 10 kHz with limitation that the longest pulse does not exceed 10% of the duty cycle. The power difference between both echoes can be set and is as high as 60 dB. The dynamics of the echoes is better than 50 dB within the 8 ns in the rising/falling edge of the pulse (echo). The output power can be tuned by means of variable attenuators giving a range of the incoming echoes from -35 dBm to -100 dBm. The LEE can also emulate multiple returns with aforementioned dynamics.
Feasibility of a 3U CubeSat for uplink quantum communications
Author(s):
Sebastian P. Neumann;
Siddarth K. Joshi;
Thomas Scheidl;
Roland Blach;
Carsten Scharlemann;
Sameh Abouagaga;
Daanish Bambery;
Erik Kerstel;
Mathieu Barthelemy;
Rupert Ursin;
Matthias Fink
Show Abstract
In the absence of technically mature quantum repeaters, losses in optical fibers limit the distance for ground-bound quantum key distribution (QKD). One way to overcome these losses is via optical links to satellites, which has most prominently been demonstrated in course of the Chinese-Austrian QUESS mission. Though its findings were impressive, such a large-scale project requires massive financial and time resources. We propose a 34x10x10cm³ nanosatellite orders of magnitude cheaper which is able to perform QKD in a trusted-node scenario, using only commercially available components.
We have performed a detailed analysis of such a CubeSat mission (“Q
3Sat”), finding that cost and complexity can be reduced by sending the photons from ground to satellite, i.e. using an uplink. Calculations have been done for a prepare-and- send protocol (BB84 with decoy pulses) using polarization as information carrier. We have created a preliminary design of a 3U CubeSat including a detailed size, weight and power budget and a CAD to account for the assembly of the components. Deploying a 10 cm long mirror telescope covering the small surface of the satellite leaves enough space for a polarization analysis module and housekeeping, communication and computing electronics.
For one such CubeSat, we estimate the quantum secure key to be acquired between two ground stations during one year to be about 13 Mbit. A Bell test between ground and satellite would also be feasible. The uplink design allows to keep the more sensitive, computation-intensive and expensive devices on ground. The experiment proposed by us therefore poses a comparably low-threshold quantum space mission. For a two-year lifetime of the satellite, the price per kilobit would amount to about 20 Euro. In large constellations, Q
3Sats could be used to establish a global quantum network, which would further lower the cost. Summarizing, our detailed design and feasibility study can be readily used as a template for global-scale quantum communication.
Space-to-ground quantum key distribution
Author(s):
T. Scheidl;
J. Handsteiner;
D. Rauch;
R. Ursin
Show Abstract
Quantum key distribution (QKD) can in principle offer unconditional security by making use of the fundamental laws of quantum mechanics. In practice, this is typically achieved by preparing individual photons in quantum superposition states and sending them to a remote receiver. To date, most commercially available QKD systems rely on the transmission of the photons via optical fibers, which, due to channel loss and detector noise, limits the distance over which QKD is feasible to a few hundred kilometers. Alternatively, satellite-based QKD facilitates low photon loss and negligible signal disturbance and offers a viable solution for establishing a global scale quantum network. Recently, a quantum science mission of the Chinese Academy of Sciences (CAS) in collaboration with the Austrian Academy of Sciences (AAS) and the University of Vienna aimed at a satellite-based intercontinental quantum-key relay. Using the Chinese Quantum Science Satellite “Micius” as a trusted relay, a quantum network consisting of three optical ground stations located in China (Xinglong, Nanshan) and Austria (Graz-Lustbühel) has been demonstrated successfully. Here we report on the development of a quantum receiving module, installed at the Satellite Laser Ranging Station in Graz (Austria) capable of implementing the so-called decoy-state QKD protocol in a downlink scenario from the LEO satellite “Micius”. Furthermore, we will present the experimental results obtained during several downlinks from the Chinese satellite focusing on the performance of the Austrian receiving station.
Effects of atmospheric turbulence and misalignment-induced fading on the secrecy performance of IM/DD free-space CV-QKD systems using a Gaussian beam
Author(s):
Phuc V. Trinh;
Alberto Carrasco-Casado;
Anh T. Pham;
Morio Toyoshima
Show Abstract
This paper explores the secrecy performance of the recently proposed intensity modulation/direct detection (IM/DD) terrestrial free-space quantum key distribution (QKD) system, by using a Gaussian-beam propagation model and considering the combined effects of atmospheric turbulence and legitimate transceivers’ misalignment. Secrecy performance metrics including quantum bit error rate (QBER) and ergodic secret-key rate are newly derived in closedform expressions, taking into account all combined effects of turbulence- and misalignment-induced fading channels, the eavesdropper’s location relative to the legitimate receiver, and receiver noises. To satisfy security constraints, the system designs based on the intensity modulation depth and beam waist of the Gaussian beam at the transmitter, and dualthreshold (D-T) selection at the receiver, are comprehensively discussed under turbulence and misalignment conditions as well as different eavesdropper’s locations. Monte-Carlo (M-C) simulations are also implemented to verify the analytical results. Remarkably, this paper also offers the first framework in the literature to evaluate the secrecy performance of free-space optical (FSO) systems considering the eavesdropper’s location under the effect of misalignment between legitimate transceivers.
Technologies and designs for small optical missions
Author(s):
A. Zuccaro Marchi;
L. Maresi;
M. Taccola
Show Abstract
ABSTRACT The worldwide growing interest in small payloads and platforms require the use of solutions that are compact, cost effective and simple to align and test. In particular, the possibility to use constellations of small satellites require the payloads to be easily built in a relatively large number compared to typical space missions where only the flight model and possibly few flight spares need to be procured. This clearly drives the payload architecture towards solutions that can be easily manufactured, and in large quantities.
The recent progress of manufacturing techniques favours this rapid change. For instance, for some applications the possibility to use a spectrometer with a magnification different from one is a key factor to enable instrument designs that are compact, cost effective and with high performance. This can be for instance achieved by using freeform or aspheric mirrors and freeform or spherical gratings. Other compact designs use instead linearly variable filters as dispersive devices, pointing to a different set of applications and performance.
The progress on small satellites and payloads, especially in the vision of large constellations, also benefits from the rapid development of imaging processing and deep learning machines, for instance equipping the payloads with powerful onboard data processor for real time generation of Level 2 data to face the challenge of handling the huge amount of data that is produced on-board.
By combining all these developments, it is possible to produce a portfolio of innovative multi/hyperspectral payloads covering a broad range of applications, spanning from high spatial resolution to large swath width, from minisatellite to cubesat format. Exploiting the flexibility and interoperability of these payloads, the users will be provided with turnkey solutions and real time response to their specific needs.
The European Space Agency is leading several R&D activities in the field of compact multispectral and hyperspectral payloads, fit for small platforms. These activities encompass technology development of novel optical designs, materials and processes, including also engineering of detectors, EEE components and dedicated data processing to achieve innovative and cost-effective solutions.
The paper provides an overview of the technology developments, the status of the instruments manufactured so far and those in operation, their performance and their expected applications. An example of an imaging spectrometer design that is extremely compact, realized with only two spherical optical elements and with a magnification different from one (1:3) is also addressed.
In-orbit demonstration of the first hyperspectral imager for nanosatellites
Author(s):
M. Esposito;
A. Zuccaro Marchi
Show Abstract
HyperScout-1 is the first smart hyperspectral imager for nanosatellites. It has been launched on the 2
nd of February 2018 at 8:51 CET, from the Jiuquan Satellite Launch Center in China. The launch vehicle Long March 2D lifted off on schedule and the satellite was separated from the launch vehicle minutes later. Approximately after 6 hours the first contact was established.
HyperScout-1 is based on a long line of development led by cosine measurement systems. The project to develop, build and launch the first HyperScout-1 was funded by ESA, with support from the Dutch, Belgian and Norwegian national space organizations: Netherlands Space Office, BELSPO and Norsk Romsenter. cosine, as the prime contractor, enlisted the help of consortium partners S&T, TU Delft, VDL and VITO.
The aim of the demonstration mission is to assess the quality of the data that will be acquired and the consequent suitability for the intended applications. Furthermore, the basic functionalities of the instrument as well as the onboard processing in real time will be demonstrated. The demonstration is divided in three operational blocks, during which HyperScout® will be operated to acquire data from invariant sites for vicarious calibration, from application sites to qualify HyperScout® for all the applications it has been conceived for, and to perform software experiments to demonstrate the novel approach to overcome the bandwidth limitation on small platforms.
NanoCarb part 1: compact snapshot imaging interferometer for CO2 monitoring from space
Author(s):
Yann Ferrec;
Guillaume Bonnery;
Laure Brooker;
Laurence Croizé;
Silvère Gousset;
Etienne Le Coarer
Show Abstract
Nanocarb is a snapshot imaging interferometer concept dedicated to the measurement of CO2. Thanks to its very compact design, it is a good candidate for small satellites, which would pave the way to a constellation of satellites to monitor emission of anthropogenic greenhouse gases from space. Nanocarb is based on a multiaperture design, with a stepcase interferometric plate to measure partial interferograms. It is developed in the framework of the Scarbo project, an European project involving several partners, the aim of which being to design and analyse the performances of the Nanocarb concept, complemented by collocated compact aerosol sensor and CO2 reference instruments. The overall measurement concept will be experimentally validated through a dedicated airborne campaign featuring instrument prototypes.
Freeform optics design tool for compact spectrometers
Author(s):
M. David Nijkerk;
J. Michael Gruber;
Bart Boonacker
Show Abstract
We present a novel optical design tool that makes use of an evolutionary global optimization algorithm. The algorithm has several characteristics that make it well-suited for freeform optics design. With the design tool it is no longer necessary to make the distinction between paraxial degrees of freedom and degrees of freedom related to freeform surface description. The design process, which typically involves a multi-stage scheme consisting of finding an optimal paraxial starting layout, optimization, gradually including freeform degrees of freedom to yield an optimal nominal design, and finally a step in which the as-built design is optimized, is shortened because optimal paraxial starting point and optimal freeform shapes are combined to a single optimization step. Optionally, as-built performance can be included in this step as well. The design tool is applied to the design of a compact spectrometer.
X-ray testing at PANTER of optics for the ATHENA and Arcus Missions
Author(s):
Vadim Burwitz;
Marcos Bavdaz;
Eric Wille;
Max Collon;
Giuseppe Vacanti;
Nicolas Barriere;
Giuseppe Valsecchi;
Fabio Marioni;
Dervis Vernani;
Thibault Seure;
Steffen Blum;
Richard Willingale;
Randall Smith;
Casey de Roo;
Ed Hertz;
Gisela Hartner;
Marlis-Madeleine La Caria;
Carlo Pelliciari;
Andreas Langmeier;
Stefan Felix Hartl
Show Abstract
Currently for the European Space Agency (ESA) ATHENA [1,2] mission Silicon Pore Optic (SPO) [3-8] Mirror Modules (MM) with a focal length of f = 12 m, are being developed and tested. The SPO MMs are also the baseline optic for the NASA medium explorer high-resolution spectroscopy mission Arcus [9-10] with f = 12 m that is currently undergoing a phase A study. SPOs are currently being tested at both the PTB laboratory of the BESSY synchrotron facility in Berlin using an X-ray pencil beam and the PANTER X-ray test facility in Neuried of the Max-Planck-Institut für extraterrestrische Physik, Garching using a long vacuum beamline (distance source to optic ~120 m). The different types of measurements performed at PANTER to characterise the ATHENA and Arcus optics will be discussed. This will be done on the level of an X-ray optical unit (XOU) composed of both a primary and secondary High Performance Optic (HPO) stack, a mirror module (MM) composed of two XOUs, small (<4 MMs) and large (< 25 MM) petals, and the complete integrated optic Athena (700-1000 MMs) and Arcus (4 petals each with 38 MMs). The main set of tests that are currently done at PANTER make full use the possibility to fully-illuminate single XOUs, MMs, and petals to determine their optical characteristics such as the half energy width of the point spread function as well as the effective area and the vignetting function at different energies. To ensure that the measurements, that are required to demonstrate the performance of ATHENA, are possible, a description of recent and upcoming upgrades to the PANTER X-ray test facility will be given. Finally, a status update on the progress on designing the new facility to be used to test and calibrate the complete ATHENA mirror will be presented.
A vertical facility based on raster scan configuration for the x-ray scientific calibrations of the ATHENA optics
Author(s):
G. Pareschi;
A. Moretti;
B. Salmaso;
G. Sironi;
G. Tagliaferri;
M. Uslenghi;
M. Fiorini;
P. Attinà;
R. Bressan;
G. Marchiori;
M. Tordi;
F. Marioni;
G. Valsecchi;
F. Zocchi
Show Abstract
The ATHENA X-ray observatory is a large-class ESA approved mission, with launch scheduled in 2028. The technology of Silicon Pore Optics (SPO) was selected since 2004 as the baseline for making the X-ray Mirror Assembly. Up to 700 mirror modules to obtain a nested Wolter like optics. The maximum diameter of the shells will be 2.5 m while the focal length is 12 m. The requirements for on-axis angular resolution and effective area at 1 keV are 5 arcsec HEW and 1.4 m2, while the field of view will be 40 arcmin in diameter (50 % vignetting). While in this moment there an on-going effort aiming at demonstrating the feasibility of a so large optics with so stringent scientific requirements, an important aspect to be considered regards the scientific calibrations of the X-ray optics. In this respect, the Point Spread Function and effective area have to be correctly measured and calibrated on-ground at different energies across the entire field of view, with a low vignetting. The approach considered so far foresees the use of a long (several hundreds of meters) facility to allow a full illumination with low divergence of the entire optics module (or at least of large sections of it). The implementation of similar configurations in a completely new facility to be realized in Europe (friendly called "super Panter") or the retrofitting existing facilities like the XRCF at NASA/MSFC are being considered. In both cases the costs and the programmatic risks related to the implementation of these huge facilities, with their special jigs for the alignment of the ATHENA optics, represent important aspects to be considered. Moreover, the horizontal position of the optics to be used in full illumination facilities would determine gravitational deformations, not easy to be removed with actuators or by modeling. In this talk we will discuss a completely different concept, based on the mount of the optics in vertical position and the use of a raster scan of the ATHENA optics with a small (a few cm2 wide) highly collimated (1 arcsec or so) white beam X-ray. This system will allow us to operate a much compact system. The use of a vertical configuration will imply smaller gravitational deformations, that can be controlled with actuators able to compensate them. A proper camera system with a sufficient energy resolution will be able to grant a correct measurement of both PSF and effective area of the Mirror Assembly within the calibration requirements and in a reasonable integration time. Moreover, it may allow us also to perform end-to-end tests using the two flight focal plane instruments of ATHENA. The cost and risks for the implementation would be much lower than for the full illumination systems. The conceptual configuration and preliminary expected performance of the facility will be discussed.
BEaTriX (Beam Expander Testing X-ray facility) for testing ATHENA's SPO modules: advancement status
Author(s):
B. Salmaso;
S. Basso;
M. Ghigo;
E. Giro;
G. Pareschi;
D. Spiga;
G. Tagliaferri;
G. Vecchi;
C. Pelliciari;
V. Burwitz;
M. Sanchez del Rio;
C. Ferrari;
A. Zappettini;
M. Uslenghi;
M. Fiorini;
G. Parodi;
M. Ayre;
M. Bavdaz;
I. Ferreira;
E. Wille
Show Abstract
ATHENA Silicon Pore Optics (SPO) Mirror Modules (MM) have to be tested and accepted prior to integration in the full ATHENA Mirror Assembly (MA). X-ray tests of the MMs are currently performed at the PTB laboratory of the BESSY synchrotron facility in pencil beam configuration, but they require a PSF reconstruction. Full illumination X-ray tests could be performed using a broad, low-divergent X-ray beam like the one in use at PANTER (MPE, Neuried, Germany), but the large volume to be evacuated makes it impossible to perform the functional tests at the MMs production rate (3 MM/day).
To overcome these limitations, we started in 2012 to design a facility aimed at generating a broad (170 x 60 mm2), uniform and low-divergent (1.5 arcsec HEW) X-ray beam within a small lab (∼ 9 x 18 m2), to characterize the ATHENA MM. BEaTriX (the Beam Expander Testing X-ray facility) makes use of an X-ray microfocus source, a paraboloidal mirror, a crystal monochromation system, and an asymmetrically-cut diffracting crystal for the beam expansion. These optical components, in addition to a modular low-vacuum level (10-3 mbar), enable to match the ATHENA SPO acceptance requirements.
The realization of this facility at INAF-OAB in Merate (Italy) is now on going. Once completed, BEaTriX can be used to test the Silicon Pore Optics modules of the ATHENA X-ray observatory, as well as other optics, like the ones of the Arcus mission. In this paper we report the advancement status of the facility.
The challenges of measuring methane from space with a lidar
Author(s):
H. Riris;
K. Numata;
S. Wu;
M. Fahey;
B. Gonzalez;
X. Sun;
J. Mao;
M. Rodriguez
Show Abstract
The global and regional quantification of methane fluxes and identification of its sources and sinks has been highlighted as one of the goals of the NASA 2017 Earth Science Decadal Survey. Detecting methane from space and airborne platforms with an active (laser) remote sensing instrument presents several unique technology and measurement challenges. The instrument must have a single frequency, narrow-linewidth light source, and photon-sensitive detector at the right spectral region to make continuous measurements from orbit, day and night, all seasons and at all latitudes. It must have a high signal to noise ratio and must be relatively immune to biases from aerosol/cloud scattering, spectroscopic and meteorological data uncertainties, and instrument systematic errors.
At Goddard Space Flight Center (GSFC), in collaboration with industry, we have developed an airborne instrument to measure methane. Our instrument is a nadir-viewing lidar that uses Integrated Path Differential Absorption (IPDA), to measure methane near 1.65 μm. We sample the absorption line using multiple wavelengths from a narrow linewidth laser source and a sensitive photodetector. This measurement approach provides maximum information content about the CH4 column, and minimizes biases in the XCH4 retrieval.
In this paper, we will review our progress to date and discuss the technology challenges, options and tradeoffs to measure methane from space and airborne platforms.
MERLIN: overview of the design status of the lidar Instrument
Author(s):
Christian Wührer;
Christopher Kühl;
Stefano Lucarelli;
M. Bode
Show Abstract
The Methane Remote Sensing LIDAR Mission (MERLIN) is a joint French-German cooperation on the development, launch and operation of a climate monitoring satellite, executed by the French Space Agency CNES and the German DLR Space Administration. It is focused on global measurements of the spatial and temporal gradients of atmospheric Methane (CH4) with a precision and accuracy sufficient to constrain Methane fluxes significantly better than with the current observation network.
Merlin is a LIDAR Instrument using the IPDA principle. This instrument principle relies on the different absorption of the laser signal by atmospheric Methane at two laser wavelengths – on-line and off-line – both around 1.645 μm, reflected by the Earth surface or by cloud tops. The attenuation is strong at the on-line wavelength; the off-line “reference” wavelength is selected to be only marginally affected by Methane absorption. Being an active instrument with its own light source, the MERLIN LIDAR Instrument does not have to rely on sun illumination of the observed areas and can therefore continuously operate over the orbit.
Airbus DS GmbH was selected by the German DLR Space Administration as the industrial Prime Contractor for the Mission Phase C/D, to build the MERLIN Payload, which is the first realization of such an instrument for space in Europe.
This presentation will concentrate on the Architecture and the Design of the MERLIN Payload developed during the ongoing Mission Phase C. Further details of the instrument development status will be shown by an overview of the current hardware and design status of the major subsystems.
Demonstration of a compact and universal Doppler lidar based on a novel diode pumped alexandrite ring laser
Author(s):
J. Höffner;
M. Strotkamp;
A. Munk;
B. Jungbluth
Show Abstract
First atmospheric measurements with a diode pumped alexandrite ring laser in a ground-based general-purpose Doppler lidar demonstrates high-resolution spectral measurements with minimum hardware requirements. Two decades of Doppler measurements by flash lamped pumped alexandrite ring laser within the worldwide only existing mobile Doppler resonance lidar have shown the capability of such scanning lidar to measure any spectrum from the troposphere to the thermosphere without a frequency reference at the wavelength of desire. An improved second-generation system with a size of 1 m3, including a 50 cm telescope, is currently under development for ground-based automatic observations at harsh environments, such as Antarctica. Minimizing the size, complexity, maintenance time and improving the optical setup pave the way of this technology for future space missions. As an example for a possible future space mission, we discuss a mesospheric potassium resonance Doppler lidar by extrapolating the signal from ground-based measurements.
Robust optical design for optimal performance of the MERLIN lidar instrument
Author(s):
Susanne Nikolov;
Werner Hupfer;
Christian Wührer;
Gerald Mathe;
Alexander Sohmer;
Stefano Lucarelli;
Arnaud Chiri;
Andreas Allgaier;
Wolfgang Holota;
Nicolas Paulin
Show Abstract
The optical design for the MERLIN instrument was driven by a concept which ensures reliable, high performance operation of the bi-static DIAL, consisting of separate transmitter (TX) and receiver paths (RX). The MERLIN satellite is a secondary passenger payload on the launcher. As such, the satellite places many constraints on the instrument, pertaining to the power, mass and volume allowable. The available resources force the MERLIN instrument to have passive thermal control while necessitating a very compact design due to the demanding envelope constraints. This creates a large operational temperature range with thermal gradients on the structure, requiring an extremely robust optical design in a compact envelope. Typically, a compact envelope requirement drives an optical design towards tight tolerances, which is in contradiction with a large operational temperature range.
The robust optical design, for the RX- and TX-paths, employs several passive measures and an active pointing control for RX and TX co-alignment. These actions are necessary to ensure good instrument performance, despite the demanding environmental requirements. Presented here will be selected load case examples for the entire design and analysis chain, from the instrument performance model towards optical, structural and thermal design.
Optical feeder link architectures for very HTS: issues and possibilities
Author(s):
Pantelis-Daniel Arapoglou;
Nicolas Girault
Show Abstract
The paper deals with an analysis of very High Throughput Satellite (VHTS) systems employing optical feeder links. To do so, a fixed set of user requirements is selected that allows for different optical feeder link options to be compared and evaluated on a common basis. The main system aspects are discussed and a rough assessment of the payload resources in terms of mass, power and dissipated power required for each is provided. This exercise reveals important trade-offs and new research avenues for the optical communications community.
Adaptive optics pre-compensation for GEO feeder links: the FEEDELIO experiment
Author(s):
A. Montmerle Bonnefois;
J. -M. Conan;
C. Petit;
C. B. Lim;
V. Michau;
S. Meimon;
P. Perrault;
F. Mendez;
B. Fleury;
J. Montri;
N. Védrenne
Show Abstract
Adaptive-Optics (AO) pre-compensation of atmospheric turbulence effects is one of the most promising technologies for achieving very high throughput optical GEO feeder links. However, its great performance has been proven mostly through numerical simulations until now, and experimental work on the subject is still at a very preliminary stage [1]. The FEEDELIO experiment (FEEDELIO for FEEDEr Link adaptive Optics), contracted to ONERA by ESA and described in this paper, goes one step further towards an experimental validation of this concept.
This paper describes the experimental implementation of an AO pre-compensated link on a 13 km slant path in Tenerife, Canary Islands. This experiment is designed to be representative of a GEO feeder link, and aims at demonstrating a significant increase of the mean received power and decrease of the power fluctuations thanks to AO. It will also allow to study the impact of the point-ahead angle on overall performance of the AO system.
The FEEDELIO experiment is planned for spring 2019.
Adaptive optics pre-correction for optical feeder links: breadboard performance
Author(s):
Rudolf Saathof;
Remco den Breeje;
Wimar Klop;
Niek Doelman;
Thijs Moens;
Michael Gruber;
Tjeerd Russchenberg;
Federico Pettazzi;
Jet Human;
Ramon Mata Calvo;
Juraj Poliak;
Ricardo Barrios;
Mathias Richerzhagen;
Ivan Ferrario
Show Abstract
For the next generation of very high throughput communication satellites, TNO and DLR envision optical free-space communication between ground stations and geostationary telecommunication satellites to replace the traditional RF links. To mitigate atmospheric turbulence, an Adaptive Optics (AO) system will be used to apply uplink pre-correction. OFELIA, an ground terminal breadboard was developed to demonstrate the pre-correction principle over an realistic link. Currently, integration tests have been performed to verify the AO performance. Also a laser link experiment over 10 km distance has already been established, in a scenario relevant to ground-to-satellite links. The paper shows that AO is clearly beneficial for the downlink performance. In addition the first preliminary experimental results of the pre-correction show it is also beneficial for the uplink.
How effective is tip-tilt pre-compensation for optical uplinks based on the received downlink optical signal?
Author(s):
D. Alaluf;
J. M. Perdigues Armengol;
Z. Sodnik
Show Abstract
This paper investigates the effectiveness of pre-compensating the beam wander effect (tip-tilt distortion) experienced by an uplink optical signal, from a ground station to a satellite, based on the tip-tilt information of the downlink signal (from the satellite to the ground). A test campaign was carried out in May 2018 at the Optical Ground Station (OGS) of the European Space Agency (ESA), to perform measurements of double stars featuring angular separations representative of the point-ahead angle of GEO/LEO satellites. The purpose of gathering these measurements is to investigate the relationship between double stars angular separation and their differential tip-tilt distortion. This analysis evaluates the influence of the point-ahead angle of the satellite, on the tip-tilt correlation between the uplink and the downlink signals. This paper describes the algorithm used to determine the tip-tilt error due to anisoplanatism, and presents the preliminary results that were extracted from the measurements. Then, it is shown how to estimate the jitter of the telescope from the common motion of two independent stars as seen in the focal plane of the telescope. Finally, the paper provides a methodology to determine the maximum transmitter aperture diameter of a ground-based laser communication terminal, in case tip-tilt pre-compensation is applied to the uplink signal based on the received satellite signal.
Stray light reduction of silicon particle reinforced aluminum for optical systems
Author(s):
Jan Kinast;
Alexander Telle;
Sven Schröder;
Marcus Trost;
Stefan Risse
Show Abstract
Silicon particle reinforced aluminum containing 42 wt.% silicon (Al-42Si) offers higher specific stiffness, higher resistance to thermal gradients, and an athermal behavior combined with electroless nickel, in comparison to state-of-the-art aluminum alloys (e.g. Al6061). Nevertheless, typical surface modifications (e.g. black anodization) lead to a nonsufficient optical stray light suppression due to the high amount of silicon particles on the surface. Therefore, a coating technique is required that fulfils the optical and the mechanical (e.g. adhesive strength) specifications for stray light reduction on Al-42Si. Different components like housings and barrels made of Al-42Si were coated with amorphous NiP and with Fractal Black™ by Acktar Ltd. The optical performance is analyzed by angle-resolved light scattering (ARS) at two different wavelengths (532 nm and 1064 nm). Fractal Black™ offers a total scattering level of lower than 2 % at 532 nm and 1064 nm. Fractal Black™ has been proven as a suitable coating for components made of Al-42Si.
Straylight analysis on ASPIICS, PROBA-3 coronagraph
Author(s):
C. Galy;
C. Thizy;
Y. Stockman;
D. Galano;
R. Rougeot;
R. Melich;
S. Shestov;
F. Landini;
A. Zukhov;
V. Kirschner;
P. Horodyska;
S. Fineschi
Show Abstract
PROBA-3 is a mission devoted to the in-orbit demonstration (IOD) of precise formation flying (F²) techniques and technologies for future ESA missions. The mission includes two spacecraft. One of them will act as an external occulter for scientific observations of the solar corona from the other spacecraft, which will hold the ASPIICS coronagraph instrument, under CSL responsibility.
The ASPIICS instrument on PROBA-3 looks at the solar corona through a refractive telescope, able to select 3 different spectral bands: Fe XIV line @ 530.4nm, He I D3 line @587.7nm, and the white-light spectral band [540;570nm]. The external occulter being located at ~ 150 meters from the instrument entrance, will allow ASPIICS to observe the corona really close to the solar limb, probably closer than any internally or externally occulted coronagraph ever observed.
This paper will present the straylight model and analyses carried out by CSL. A first specificity of the analysis is that the scene on the useful Field of View (FOV) is the solar corona which has a brightness dynamic range as high as 10
3 between the close corona, close to 1 solar radius (Rsun), and the “distant” corona around 3RSun. The specifications are very stringent for this type of instrument. A consensus was found and will be presented regarding the expected straylight within the FOV. It will also be shown that to achieve realistic estimations it is required to take into account the exact location of the created straylight as well as the entrance field.
The second specificity that had to be analyzed is that the diffraction from the solar disk by the external occulter enters the instrument un-obstructed until the internal occulter, and with a brightness 100 times higher than the close corona (~1RSun) brightness. The simulation of this diffraction as well as its propagation inside the ASPIICS telescope creating additional straylight, had to be carefully established in order to give realistic results of its impact on the performances while being actually possible to compute.
Stray light calibration for the Solar Orbiter/Metis solar coronagraph
Author(s):
F. Landini;
M. Romoli;
S. Fineschi;
C. Casini;
C. Baccani;
E. Antonucci;
G. Nicolini;
G. Naletto;
P. Nicolosi;
D. Spadaro;
V. Andretta;
M. Castronuovo;
M. Casti;
G. Capobianco;
G. Massone;
R. Susino;
V. Da Deppo;
F. Frassetto;
M. Pancrazzi;
L. Teriaca;
U. Schuehle;
K. Heerlein;
M. Uslenghi
Show Abstract
The Solar Orbiter/Metis visible and UV solar coronagraph redefines the concept of external occultation in solar coronagraphy. Classical externally occulted coronagraphs are characterized by an occulter in front of the telescope entrance aperture. Solar Orbiter will approach the Sun down to 0.28 AU: in order to reduce the thermal load, the Metis design switches the positions of the entrance aperture and the external occulter thus achieving what is called the inverted external occultation. The inverted external occulter (IEO) consists of a circular aperture on the Solar Orbiter thermal shield that acts as coronagraph entrance pupil. A spherical mirror, located 800 mm behind the IEO, back rejects the disklight through the IEO itself. To pursue the goal of maximizing the reduction of the stray light level on the focal plane, an optimization of the IEO shape was implemented.
The stray light calibration was performed in a clean environment in front of the OPSys solar disk divergence simulator (at ALTEC, in Torino, Italy), which is able to emulate different heliocentric distances. Ground calibrations were a unique opportunity to map the Metis stray light level thanks to a pure solar disk simulator without the solar corona. The stray light calibration was limited to the visible light case, being the most stringent. This work is focused on the description of the laboratory facility that was used to perform the stray light calibration and on the calibration results.
Modelization, measurement and correction of a cross-talk image ghost in the Ingenio/SEOSAT payload
Author(s):
C. Miravet;
C. Santos;
D. Zorita;
D. Gil-Leyva;
I. Cabeza;
A. Marini;
F. Reina;
V. Kirschner;
A. Popescu
Show Abstract
Ingenio/SEOSAT is a high-spatial-resolution optical mission developed under the Spanish Earth Observation National Program for Satellites (PNOTS), and managed technically in the framework of an ESA contract. It features as Primary Payload (PP) a high-resolution optical payload with one 2.5 meter resolution panchromatic channel and four 10 meter resolution visible/near infrared spectral channels. It is based on a twin Korsch telescope concept, each telescope covering half of the instrument’s swath width. In this communication is presented a detailed account of the work performed to accurately characterize and correct by post-processing an image ghost present in the multi-spectral channels of the primary payload. The work reported here includes the description and analysis of the results of three test campaigns, performed at Thales Alenia Space. Tests carried out include radiometric tests at focal plane level, generic stray-light tests and a novel test to characterize specifically the parameters of the studied cross-talk image ghost. Field-dependent point spread functions for the studied image ghost have been generated by optical analysis, and have been adjusted with the results of the performed tests. From these, image filters have been devised to reproduce, and remove by subtraction, the image ghost. Quantitative image ghost correction results on an actual test image are shown.
Time-of-flight calibration of an MCT-APD sensor for a flash imaging LiDAR system
Author(s):
Victor E. S. Parahyba;
Eric de Borniol;
Regis Perrier;
Yoanna-Reine R. Nowicki-Bringuier;
Alessandra Ciapponi;
Jocelyn Chanussot
Show Abstract
Flash Imaging LiDARs (Light Detection and Ranging) are active systems that resolves depth in a scene by time-of-flight measurements and are being seen as a competitive technological alternative that presents great advantages in the space scenario. The system records full 3D-images with a single laser pulse, thus eliminating the need for a scanning device.
A first step to improve the overall quality of the measurements is the calibration of the camera. There is a vast literature and well-stablished techniques concerning radiometric calibration (2D information). However, for time-of-flight (3D information) the subject remains open to improvement and dependent upon the specific characteristics of the detector. In this article we propose a calibration scheme for CEA-LETI’s LiDAR that combines both intensity, range accuracy and range precision calibration and presents the first enhanced results based on data acquired under laboratory conditions.
This project is a partnership between ESA and CEA-LETI aiming the design of a LiDAR system based on a custom MCTAPD FPA (Avalanche PhotoDiode Focal Plane Array) detector developed by CEA-LETI and the formulation of a set of imaging processing algorithms. The target is to demonstrate the potential of such detector technology and to evaluate the performances of the full system chain in the frame of the targeted application. In the future, a validation campaign on a real terrain, at ESA’s campsite, will be performed to demonstrate the system in a close-to-real configuration.
Flight design of the absolute frequency reference unit for the methane-sensing LIDAR Mission MERLIN
Author(s):
Show Abstract
Light detection and ranging (LIDAR) systems have become an important technology in a variety of industrial and scientific applications. In spectroscopy, LIDAR systems can improve the sensitivity by orders of magnitude but require the laser source to have a sufficient small linewidth and stability. For terrestrial applications, such systems have been developed over the last decade and are commercially available. In space, this technology does not have a comparable maturity level and is still far from being a standard technology. In this paper, we present the design and first measurement results of a spaceborne absolute frequency reference based on the absorption feature at 1645.55 nm of methane gas. The frequency reference unit is used in the instrument of the French-German Methane Remote Sensing LIDAR Mission, MERLIN. It provides the stabilized seed lasers for the high power laser sources at the required wavelengths and measures the absolute frequency of the outgoing laser pulses by means of a wavemeter.
IPDA LIDAR measurements on atmospheric CO2 and H2O using dual comb spectroscopy
Author(s):
Jérémy Oudin;
Ajmal Khan Mohamed;
Philippe-Jean Hébert
Show Abstract
We are developing an Integrated Path Differential Absorption (IPDA) LIDAR based on dual comb spectroscopy and recently achieved measurements of 𝐶𝑂2and 𝐻2𝑂 concentrations over 280 meters in the atmosphere. High repetition rate (100 MHz) femtosecond fiber laser frequency combs with spectral bandwidth over 100 nm around 1550 nm are used.
In-field and Out-of-field stray light analysis for the COPERNICUS Sentinel 4 instrument
Author(s):
S. Grabarnik;
G. Bazalgette Courrèges-Lacoste;
C. Pachot;
L. Gambicorti;
R. Rivière;
Stefan Riedl
Show Abstract
Sentinel-4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus Defence and Space as prime contractor under ESA contract in the frame of the joint EU/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate applications. Stray light, which is unwanted light captured by the detectors, is one of the major contributors to such important instrument performance metrics as absolute and relative spectral and spatial radiometric accuracies. Amongst the different sources of stray light, Out-of-Band stray light can not be corrected. It is thus important to ensure its impact is limited. The main scope of this paper is to describe the stray light simulations performed in the frame of the Sentinel-4 project: the models, analysis approach and the results. Also, the technical challenges faced in building the models and performing the analysis and the solutions found to solve them are presented.
Evaluation of straylight characteristics of the Sentinel-5 NIR spectrometer optics
Author(s):
M. Merschdorf;
L. Platos;
P. Petruck;
B. Michel;
B. Harand
Show Abstract
Jena-Optronik GmbH is developing the Sentinel-5 NIR spectrometer optics operating in the spectral range from 685 nm to 773 nm. It is purely based on refractive optics and makes use of a grating as dispersive element and a prism for aberration correction. One of the design drivers for the optics design is straylight as small absorption effects in the atmosphere need to be detected. To minimize false light on the detector the straylight characteristics have been analyzed and optimized together with Hembach Photonik GmbH. Special attention needs to be paid to the dispersive nature of the optics as compared to a pure imaging system. Sources of ghosts and scattered light such as surface roughness, particle contamination and scattering at mechanical surfaces are quantified. Main contributors to straylight are identified and strategies for straylight reduction are discussed. Among others this comprises effective means to suppress out-of-band light.
Modelization and validation of the diffraction effects in the Microcarb instrument for accurately computing the instrumental spectral response function
Author(s):
M. Castelnau;
E. Cansot;
C. Buil;
V. Pascal;
V. Crombez;
S. Lopez;
L. Georges;
M. Dubreuil
Show Abstract
MicroCarb is a space program which uses a passive Short Wave InfraRed (SWIR) spectrometer instrument. MicroCarb will provide measurements of the atmospheric concentration of the carbon dioxide at global level with a precision sufficient in order to permit to the scientific community to improve the model of the carbon cycle by understanding the mechanisms governing the exchanges of CO2 between the sources and the sinks.
The MicroCarb Instrument is currently under development at Airbus Defense & Space (ADS). Among the spectral requirements that it must meet, some concern the Instrumental Spectral Response Function (ISRF), which is a key quantity of spectrometers, needed for spectral instrument calibration and atmospheric inversion calculations.
During the development of the Instrument, ADS proposed a method based on several Fourier Transforms to compute the ISRF, based on the one developed by R. Berlich for the FLORIS Instrument
[1], in order to have an accurate model of its spectral performances.
In this paper, we will explain the simulation method, which allows to take into account diffraction at the system entrance pupil, the spectrometer slit and the dispersion grating, and also the theoretical optical quality of the Instrument. We will describe the preliminary experiments ADS performed to validate this approach. We will then present the work done at ADS and CNES for validating and cross-checking the results of our computations, that required the use of advanced light propagation modules of CODE V.
Once validated, this tool allows to accurately compute the theoretical performances of a given working point, such as the Full-Width at Half Maximum (FWHM) of the ISRF, the resolution of the spectrometer and the likeness of the ISRF to a gaussian function. It is also a powerful tool to quickly compute many ISRFs and thus carry out trade-offs on several parameters of the instrument.
Finally, by including this static computation into a loop and by varying the radiance inside the slit, it is possible to obtain dynamic ISRFs of complex scenes on the ground, and thus have a complete and validated model of the spectral performances of the MicroCarb instrument.
PHEBUS UV spectrometer on board ESA-BepiColombo Mission: Instrument design & performance results
Author(s):
J.-F. Mariscal;
N. Rouanet;
J.-L. Maria;
B. Lustrement;
E. Bertran;
C. Montaron;
G. Guignan;
A. Reberac;
E. Quemerais;
P. Zuppella;
M. G. Pelizzo;
A. J. Corso;
I. Yoshikawa;
K. Yoshioka;
G. Murakami
Show Abstract
BepiColombo, a cornerstone mission of European Space Agency (ESA) in cooperation with the Japan Aerospace Exploration Agency (JAXA), will explore Mercury the planet closest to the Sun. This first European mission toward Mercury will be launched in October 2018 from the Guiana Space Centre, on a journey lasting up to six and a half years. The data that will be brought back from the two orbiters will tell us about Mercury’s surface, the atmospheric composition, and the magnetospheric dynamics; it will also contribute to understanding the history and formation of terrestrial planets. Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS) is a double spectrometer that will be flown on the Mercury Planetary Orbiter (MPO) one of the two BepiColombo orbiters. This French-led instrument was developed with the purpose of detecting emission lines from Mercury’s exosphere to reveal its composition and distribution, in the wide UV range 55 nm - 315 nm and by recording full spectra. In this paper, we present the instrument design by focusing on the optical subsystems and giving a technical feedback of the major challenges we had to face. We also introduce the calibration philosophy and the main performance results of the instrument.
Cheops optical calibration campaign
Author(s):
Bruno Chazelas;
Adrien Deline;
F. Wildi;
Mirsad Sarajlic;
Michaël Sordet;
Thibault Kuntzer
Show Abstract
The ESA S mission CHEOPS relies on a photometer for the precise measurement of the radius of exoplanet. This information is essential to better constrain the nature and structure of exoplanets. The CHEOPS payload is a small defocused telescope of 32-cm aperture that went through its characterization campaign in the first quarter of 2018. We report here on the techniques developed for the calibration campaign and the results of the obtained. In particular we have measured high-precision color-dependent flat fields, measured the characteristics of the detection chain, gain, full-well capacity, read-out noise, measured the instrument distortion and explored the PSF behavior across the field. The end-toend photometric stability of the instrument has also been measured and we will be reporting on the results and the difficulties that have come up while attempting this very difficult measurement, for which sophisticated design and methods were developed.
Opto-mechanical alignment results of the Euclid near infrared spectro-photometer optical assembly NI-OA
Author(s):
H. Thiele;
A. Mottaghibonab;
M. Dubowy;
A. Mecsaci;
E. Gubbini;
K. Gawlik;
F. Grupp;
D. Penka;
J. Kaminski
Show Abstract
The Euclid payload features two instruments that are observing the sky simultaneously. The visual light high spatial resolution imager (VIS) and the Near Infrared Spectrometer and Photometer (NISP). A Korsch type telescope with 1,2m diameter feeds both instruments via a dichroic beamsplitter. The NISP instrument reduces the incoming f/#20 beam of the telescope to an f/# 10 beam. The instruments optical system, the NISP Optical Assembly (NI-OA) contains 4 lenses, one single lens in front of a Grism and Filter wheel which is called collimator lens assembly (CoLA), and a lens triplet between these Grism and Filter wheel and the instruments focal plane, which is called camera lens assembly (CaLA). The focal plane consists of 16 Hawaii 2RG detectors.
The required alignment accuracy of the lens triplet and of the singlet relative to the triplet is very demanding and needs to be achieved and verified at the operational temperature of 134K. As an introduction the design, the integration and alignment concept are briefly summarized, as well as the measurement concept to verify the cold alignment within the cryostat. Alignment results for the integration of CaLA EQM and FM at room temperature are presented, the alignment stability after vibrational loads and thermal vacuum cycling is high, only minor changes of a few μm and arcsecs can be detected. The accuracy of the measured cryogenic alignment is demonstrated to be just a few μm and arcsec off the ideal predicted opto-mechanical alignment.
MESSIER: exploring the ultra-low surface brightness universe with a curved focal plane based satellite
Author(s):
S. Lombardo;
E. Muslimov;
D. Valls-Gabaud;
E. Hugot;
G. Lemaître;
M. Roulet;
M. Ferrari;
K. Joaquina
Show Abstract
The extremely low surface brightness sensitivity required to observe the ultra-low-surface brightness universe lead us to propose MESSIER, a space mission designed to drift-scan the entire sky in 6 filters covering the 200-1000 nm range and reaching unprecedented surface brightness levels of 34 and 37 mag arcsec2 in the optical and UV, respectively. Here, we present the ground-based MESSIER pathfinder aimed at testing several breakthrough technologies involved (e.g. curved detectors) and carrying out observations. We present here a detailed analysis of the optical quality achievable through photon Monte Carlo simulations of the system, including atmospheric effects.
Development of a space-based nulling interferometer to detect and characterize exoplanets
Author(s):
L. Schifano;
D. Defrère;
O. Absil;
J. Loicq
Show Abstract
The development of small space-based platforms for nulling interferometric observations could be the pathfinder of a new era in exoplanetology. While planetary transit and radial velocity are the most productive ways to detect exoplanets, such techniques are indirect detections. For deeper characterization of exoplanets, direct detection techniques should be developed. By injecting direct light coming from exoplanets into spectrometers, we could study their chemical composition, search for biosignatures, and possibly infer the presence of life.
The low number of photons to be gathered from the planets, high contrast with the star and small angular resolution are the major difficulties for a direct detection. However, nulling interferometry seems to be a solution to tackle these challenges. By combining the light of two or more telescopes, we would considerably increase the angular resolution, and thus could potentially lead to the detection of Earth-size rocky exoplanets around Solar-type stars. Moreover, with a π- phase shift between the two interferometer arms, the starlight is reduced which allows the detection of much fainter objects around the star. In this paper it will be presented the development of a new mission based on nulling interferometry and dedicated to the Alpha Centauri system. As our nearest stellar system, it is a prime target to investigate for the research of new worlds. Monte-Carlo simulations about potential exoplanet yield of such an interferometer will be described, for different assumptions such as the detection wavelength and telescope size. Single-mode fibers and integrated optics will also be investigated for this mission. This could lead to low-cost type missions with a high potential of scientific return.
Development and qualification of a miniaturised CMOS camera for space applications
(3DCM734/3DCM739)
Author(s):
C. Sellier;
D. Gambart;
N. Perrot;
E. Garcia-Sanchez;
C. Virmontois;
W. Mouallem;
A. Bardoux
Show Abstract
3D PLUS has developped in the framework of R&D activities an advanced CMOS camera for Space applications. The Centre National d’Etudes Spatiales (CNES), also called French space agency, is leading the developement of this camera, see Figure 1. This instrument has been integrated using the 3D PLUS technology [1] in order to be as compact as possible. Particular attention has been paid to ensure a good radiation tolerance to cover a wide range of scientific applications such as planetology, but also platform or launcher monitoring and star trackers
Resistance and gain of the microchannel plate (MCP) detector as a function of temperature
Author(s):
O. B. Chassela;
A. Grigoreiv;
A. Fedorov;
N. André;
E Le-Comte;
J. Rouzaud;
P. Spezzigu
Show Abstract
The microchannel plate (MCP) has been used for decades as a photon, electron and atoms detector in most of the space instruments dedicated for X-rays, energetic neutral atoms, and charged particle imaging. The deep-space missions, as nearfuture ESA Jupiter Icy moon Explorer (JUICE) mission, expect very low temperature conditions on the destination orbit. Since instruments are usually calibrated on the ground under the “room” temperature, it is very important to know the variation of the detectors properties with temperature. The resistance and the gain of the MCP detectors, dedicated for the JENI (PEP package) instrument onboard of JUICE, were measured as a function of temperature at INTRASPEC TECHNOLOGIES, Toulouse, France for the temperature range -50 to +50°C and at the CALIPSO-3 facility of the Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse, France for the temperature range -25 to +25°C using samples from PHOTONIS France and PHOTONIS USA. It is also important to know how the resistance of the MCP detector behaves with temperature either to properly size the high-voltage source or, conversely, to choose a technology according to the size of the MCP detector and the maximum current that the high-voltage source can supply. Since the environment of Jupiter is very severe, the instruments will operate in the presence of high-energy particles that will induce background noise on the MCP detectors due to the shielding of the instruments against radiation. Therefore, the background noise in the Jovian environment represents a crucial issue for the MCP detectors whose gain can be degraded prematurely if too much charge is extracted from them due to the induced particles. Ours measurements show that the resistance of the MCP detector increases when the temperature decreases and is influenced by its self-heating, whereas the gain behavior depends on the technology of the MCPs. This is an important result which can be used to optimize the gain performance and the lifetime of the MCP detector. These experimental tests were funded by the French Space Agency CNES.
High-detection efficiency MCP-PMTs with single photon counting capability for LIDAR applications
Author(s):
Dmitry A. Orlov;
Rene Glazenborg;
Raquel Ortega;
Emilie Kernen
Show Abstract
In this paper the focus is on the implementation of Photonis MCP-PMTs with single photon counting capability for LIDAR applications. In particular we are presenting our MCP-PMTs based on HI-QE photocathodes optimized for different spectral ranges (UV, Blue, Green with typical QE<30%) and for fixed laser wavelength of 355 nm and 532 nm [1]. In addition to the high QE, those photocathodes demonstrate low dark rates, typically below 50 Hz/cm2, property that is important for low-rate signal detection. The collection efficiency of the MCP is also improved to reach almost 100%, allowing to increase the detective QE by a factor of 1.5 compared to conventional MCP-PMTs [2]. The timing performance for MCP-PMTs operated at low and high rate photon fluxes are also studied. Non-linearity effects for high rate of illumination are analyzed and MCP-PMTs with extended linearity are presented. All these improved detection properties can be combined with the possibility of fast triggering and extended life time technology making these devices unique for future atmospheric and altimetry LIDAR missions.
Optimized performance of multi-level pulsed signaling with photon counting
Author(s):
Don M. Boroson
Show Abstract
Optical communications systems using pulsed optical modulations and photon-counting receivers have been demonstrated to be capable of very high photon efficiencies. The basic trade is to achieve high photon efficiency by using more bandwidth along with higher ratios of peak-to-average transmitted power. We investigate here the efficiency a photon-counting receiver could achieve in the lower bandwidth regime. It is well known that the best efficiencies at high bandwidths are achieved using two-level pulsed signaling. We will show that it is possible to achieve medium efficiencies at somewhat reduced bandwidth if the pulses are allowed to have more than one level. Equivalently, we show that at fixed slot rates, it is possible to more than double the data rates achievable by a photon-counted, pulsed optical system, although at somewhat decreased photon efficiency.
Experimental results of high power double-pass, double clad EYDFA
Author(s):
T. Araki;
E. Mizuta;
Y. Kobayashi;
Y. Takushima;
X. Wang;
S. Sekiguchi
Show Abstract
A high-power, double-pass (DP), and double-clad (DC) Erbium (Er)-Ytterbium (Yb) doped optical fiber amplifier (EYDFA) was fabricated and experimentally evaluated. Because optical amplifiers for space missions must achieve higher electrical-to-optical conversion efficiency in consideration of power consumption and heat generation, we focused on a DP optical fiber amplifier that can be expected to achieve high optical-to-optical conversion efficiency. Free-space optics and integrated design were adopted for a DP module and a Faraday mirror (FM) module, so as to ensure low transmission loss (high efficiency). The DP module including a tap mirror, isolators, and a polarizing beam splitter measured 70×50×22.5 mm in size, with transmission loss of 0.65 dB (from input port to pump combiner port) and 0.52 dB (from pump combiner port to output port). In contrast, the FM module was 40×37×18.5 mm in size, with round-trip transmission loss of 0.66 dB. The fabricated DP-DC-EYDFA achieved output power of around 7 W in the wavelength range from 1540 to 1560 nm and optical-to-optical conversion efficiency exceeding 32%. To the authors’ knowledge, this is the highest output power ever recorded by a DP-DC-EYDFA. The measured polarization extinction ratio (PER) of the fabricated DP-DC-EYDFA was 23.6 dB without using PM EYDF. And in comparison with a single-pass DC EYDFA using the same EYDF, we obtained results showing that the conversion efficiency of the DP-EYDFA was at least 4.2% higher than that of the SP-EYDFA.
Development status and breadboard results of a laser communication terminal for large LEO constellations
Author(s):
S. Müncheberg;
C. Gal;
J. Horwath;
H. Kinter;
L. Martin Navajas;
M. Soutullo
Show Abstract
Several operators plan to launch mega-constellations of several hundred or even thousands of satellites over the next years to provide global, high-speed and secure backbone communications. Most of these constellations will use a hybrid approach, with radio links for communications with the ground and free-space optical communications for inter-satellite links. First demonstration satellites were successfully launched in 2018.
Since 2009 Mynaric has successfully demonstrated high-speed laser communications in air-to-air, air-to-ground and ground-to-ground applications. Data rates up to 10 Gbps were achieved and altitudes up to 20 km were reached. First airborne terminals and ground stations for airborne and space applications were delivered to commercial customers. Building on the heritage from operations in the harsh environment of the stratosphere, Mynaric started two years ago with the development of a low-earth orbit (LEO) optical terminal for inter-satellite links.
The LEO terminal will provide a data rate of 10 Gbps full duplex over distances of up to 4500 km and a compact design with simple mechanical and thermal interfaces to the satellite bus. The Critical Design Review (CDR) shall be held in autumn 2018 and completion of the qualification is planned for 2019. A demonstration mission in LEO using two satellites is planned in 2019/2020.
Breadboard testing is in progress for several key components such as the coarse pointing assembly (elevation and azimuth axes), the fine pointing assembly and the communication subsystem. Radiation tests were successfully performed to verify the EEE parts approach using COTS and automotive components. RFI/RFP processes are being done to select key subcontractors/suppliers and to gather costing information for the recurring, high-volume serial production of the terminals.
The paper presents the design overview of the terminal and reports on the current development status. The CDR status and results of the breadboard tests are presented and an outlook towards the first demonstration in space is given.
10W single-mode PM optical amplifiers in the 1.5 μm for space applications
Author(s):
Emile Haddad;
François Gonthier;
QiYang Peng;
Viorel Poenariu;
Kamel Tagziria;
Jonathan Lavoie;
Piotr Murzionak;
Gregory Schinn;
Nikos Karafolas;
Charlotte Bringer
Show Abstract
MPB is developing space qualified 10 W End Of Life (EOL) optical amplifiers for longer range applications. Their design employs Polarization Maintaining (PM) Erbium and Erbium-Ytterbium Double Clad Fiber (EDF, EYDF) singlemode fibers. Absorption losses of the EDF and EYDF due to radiation in space are the major challenge to overcome. The gamma radiation tests show that the PM fibers have a greater sensitivity than standard fibers. However, in many applications, PM amplifiers show greater performances which is important for the power consumption.
Furthermore, MPB’s design minimizes Stimulated Brillouin Scattering in the fibers, a major obstacle to be overcome at this power level, even for on ground applications. Moreover, the compatibility with space environment (vacuum, temperature cycling, and radiation) of the high-power optical and electronic components (isolators, laser-diode pumps, current drivers) has to be demonstrated.
The proposed optical designs compensate for radiation-induced losses, without resorting to the use of expensive radiation qualified fibers- a unique method of power recuperation through the photo-bleaching of the active fiber.
an integrated payload design for the atmospheric remote-sensing infrared exoplanet large-survey (ARIEL): results from phase A and forward look to phase B1
Author(s):
Kevin F. Middleton;
Giovanna Tinetti;
Jean-Philippe Beaulieu;
Manuel Güdel;
Paul Hartogh;
Paul Eccleston;
Giuseppina Micela;
Michiel Min;
Miroslaw Rataj;
Tom Ray;
Ignasi Ribas;
Bart Vandenbussche;
Jean-Louis Auguères;
Georgia Bishop;
Vania Da Deppo;
Isabel Escudero Sanz;
Mauro Focardi;
Thomas Hunt;
Giuseppe Malaguti;
Gianluca Morgante;
Marc Ollivier;
Emanuele Pace;
Enzo Pascale;
William Taylor
Show Abstract
ARIEL (the Atmospheric Remote-sensing Infrared Exoplanet Large-survey) has been selected by ESA as the next medium-class science mission (M4), expected to be launched in 2028. The mission will be devoted to observing spectroscopically in the infrared a large population of warm and hot transiting exoplanets (temperatures from ~500 K to ~3000 K) in our nearby Galactic neighborhood, opening a new discovery space in the field of extrasolar planets and enabling the understanding of the physics and chemistry of these far away worlds. ARIEL was selected for implementation by ESA in March 2018 from three candidate missions that underwent parallel phase A studies. This paper gives an overview of the design at the end of phase A and discusses plans for its evolution during phase B1, in the run-up to mission adoption.
ARIEL is based on a 1 m class telescope feeding two instruments: a moderate resolution spectrometer covering the wavelengths from 1.95 to 7.8 microns; and a three-channel photometer (which also acts as a fine guidance sensor) with bands between 0.5 and 1.2 microns combined with a low resolution spectrometer covering 1.25 to 1.9 microns. During its 3.5 years of operation from an L2 orbit, ARIEL will continuously observe exoplanets transiting their host star.
This paper presents an overall view of the integrated design of the payload proposed for this mission. The design tightly integrates the various payload elements in order to allow the exacting photometric stability targets to be met, while providing simultaneous spectral and photometric data from the visible to the mid-infrared. We identify and discuss the key requirements and technical challenges for the payload and describe the trade-offs that were assessed during phase A, culminating in the baseline design for phase B1. We show how the design will be taken forward to produce a fully integrated and calibrated payload for ARIEL that can be built within the mission and programmatic constraints and will meet the challenging scientific performance required for transit spectroscopy.
The SuperCam infrared instrument on the NASA MARS2020 mission: performance and qualification results
Author(s):
J. -M. Reess;
Marion Bonafous;
L. Lapauw;
O. Humeau;
T. Fouchet;
P. Bernardi;
Ph. Cais;
M. Deleuze;
O. Forni;
S. Maurice;
S. Robinson;
R. C. Wiens
Show Abstract
In July 2020, NASA will launch the Mars2020 mission. This mission, very similar to the Mars Science Laboratory and its rover Curiosity, consists in landing an instrumented rover on the Martian surface in order to characterize the geology and history of a new landing site on Mars, investigate Mars habitability, seek potential biosignatures, cache samples for an eventual return to Earth, and demonstrate in-situ production of oxygen needed for human exploration.
The rover will carry several different instruments to perform field analyses in biology, climatology, mineralogy, geology and geochemistry. Among this payload, the SuperCam instrument, an improved new generation of the ChemCam instrument on Curiosity, has been developed for remote microscale characterization of the mineralogy and elemental chemistry of the Mars surface, along with the search for extant organic materials. In addition to the elemental characterization offered by Laser-Induced Breakdown Spectroscopy (LIBS), a new remote Raman spectroscopy analysis and an infrared spectrometer have been added for a complete mineralogical and chemical characterization of the samples. A context color imaging capability is also implemented to place the analyzed samples in their geological context.
SuperCam consists of three units. The “Body Unit” built by the LANL (Los Alamos National Laboratories) in the US, the “Mast Unit” built by a French consortium of 5 laboratories (IRAP as leader, LESIA, LATMOS, IAS, and LAB) funded by the French Space Agency (CNES), and a “Calibration Target Unit“ under the responsibility of the University of Valladolid in Spain.
A very compact IRS (Infrared Spectrometer) is part of the SuperCam-MU payload. The IRS concept is based on the spectral selection by an Acousto-Optic Tunable Filter (AOTF) in the 1.3-2.6 μm range with a spectral resolution better than 30 wavenumbers. The AOTF is driven by radio frequencies injected in a transducer mounted directly on a birefringent crystal. This coupling creates acoustic waves in the crystal that behave like a Bragg grating. The incident light is then diffracted in two orders (e-ray and o-ray) at the same wavelength following a so-called tuning relation law (relation between diffracted wavelength and injected radio frequency). Each diffracted order is focused on a photodiode. A complete spectrum is obtained after the scan of all individual wavelengths.
The IRS is built by LESIA and LATMOS, two French laboratories located in Paris area.
After intensive performance and qualification tests as well as a calibration on a flight-representative model, the team has built the flight model. The qualification results and the performances of the instrument are presented.
RAMAN spectrometer: development of SPU FM based on enhanced qualification model for Exomars 2020
Author(s):
J. Fco. Cabrero;
M. Fernández;
M. Colombo;
D. Escribano;
P. Gallego;
R. Canchal;
T. Belenguer;
J. García-Martínez;
J. M. Encinas;
L. Bastide;
I. Hutchinson;
A. Moral;
C. Canora;
J. A. R. Prieto;
C. Gordillo;
A. Santiago;
A. Berrocal;
F. Rull
Show Abstract
The Raman Laser Spectrometer (RLS) is one of the Pasteur Payload instruments within the ESA’s ExoMars mission. The RLS instrument scientific goal consists of perform in-situ Raman spectroscopy over different organic and mineral powder samples of the Mars subsoil. It consists of three main units: SPU (Spectrometer Unit), iOH (Internal Optical Head), ICEU (Instrument Control and Excitation Unit) which are interconnected by an optical and electrical harnesses (OH and EH).
The SPU is one of the most critical units of the RLS instrument. The Engineering Qualification Model (EQM) unit has been already delivered after a proper qualified campaign in a very demanding environment with very restrictive design constraints, including Planetary Protection requirements. Also, a complete set of functional tests had been carried out under representative environment, simulating not only Mars rover´s laboratory conditions (thermal range and pressure), but also the cruise phase. Previously, an exhaustive qualification campaign was developed with two different purposes: to mitigate the risks associated to new optical elements included in the design and without space heritage; and to obtain a detailed comprehension of their behaviour under Mars conditions for facing the Flight Model (FM) optical design with guarantee of success.
EQM results were successful in terms of Engineering, and a SWaP-optimized system had been reached. The acquired knowledge of that model has been used to implement little improvements into SPU FM for acceptance. For operations, a big amelioration has been the reduction of the image ROI on the Charge-Coupled Device (CCD) after the improving of the alignment of the inclination degree of the image plane on CCD under the tightly integration constrains, letting to download the minimum necessary data bytes. These improvements achieved by a proper analysis of the image on the SPU CCD will allow to evaluate far better the Raman spectrum effects.
SPU FM Mechanical, Thermal-Vacuum campaign has been already finished in order to accept for flight the current unit which will be already completed and “flight qualified” at RLS system level before the congress. If everything continues on this way, the desired Technology Readiness level, TRL 8 maturity level, will be reported during the following text.
Scientific objectives and observational requirements of spectrometers for main belt Comet 133P/Elst-Pizarro exploration
Author(s):
Weigang Wang;
Hao Zhang;
Bicen Li;
Jianjie Yin
Show Abstract
The discoveries of main belt comets (MBC) in early twentieth century have attracted great interests of the planetary society, as the water ice and other volatile rich MBCs are located in the main belt and thus may have played a fundamental role in supplying waters to the early Earth. Therefore, MBCs are very interesting and important candidate objects for near future deep space exploration missions. We first summarize the scientific objectives of visible and infrared spectrometers for a flyby mission. Then we propose the major technical specifications for the spectrometers, based on the optical and thermal properties of one of the major targets, 133P/Elst-Pizarro. Our proposed spectral coverage is from 0.4 to 50 μm, which is realized by two spectrometers covering 0.4-5 μm and 5-50 μm, respectively. Visible and infrared imaging spectrometer (VIIS) is a grating spectrometer covering 0.4 to 5 μm with a spectral resolution of 5 nm in the VIS/NIR band and 10 nm in the SWIR/MWIR band. The spatial resolution of the VIIS is 0.5 m at an observational distance of 5 km. The signal to noise ratio of the spectrometer is better than 100 using cryogenic optics technology. Thermal emission spectrometer (TES) is a time modulated Fourier transform spectrometer which covers5-50 μmby one single interferometer. The spectral resolution of TES is 8 cm-1. The spatial resolution of TES is 10 m at an observational distance of 5 km.
SCOPE: a coronagraph for operational space weather prediction: phase A/B1 design and breadboarding
Author(s):
Kevin F. Middleton;
Heiko Anwand;
Volker Bothmer;
Jackie A. Davies;
Andrew Earle;
Klaus Ergenzinger;
Chris J. Eyles;
Robert Hardie;
Marie-Laure Hellin;
Johannes Hinrichs;
Philipp Huke;
Piers Jiggens;
Volker Kirschner;
Emmanuel Mazy;
Thomas McCarron;
Bogdan Nicula;
Lars Stopfkuchen;
S. James Tappin;
Ian A. J. Tosh;
Nick R. Waltham;
Matthew J. West
Show Abstract
Accurate prediction of the arrival of solar wind phenomena, in particular coronal mass ejections (CMEs), is becoming more important given our ever-increasing reliance on technology. SCOPE is a coronagraph specifically optimised for operational space weather prediction, designed to provide early evidence of Earth-bound CMEs. In this paper, we present results from phase A/B1 of the instrument’s development, which included conceptual design and a program of breadboard testing.
We describe the conceptual design of the instrument. In particular, we explain the design and analysis of the straylight rejection baffles and occulter needed to block the image of the solar disc, in order to render the much fainter corona visible. We discuss the development of in-house analysis code to predict the straylight diffraction effects that limit the instrument’s performance, and present results, which we compare against commercially available analysis tools and the results from breadboard testing. In particular, we discuss some of the challenges of predicting straylight effects in this type of instrument and the methods we have developed for overcoming them.
We present the test results from an optical breadboard, designed to verify the end-to-end straylight rejection of the instrument. The design and development of both the breadboard and the test facility is presented. We discuss some of the challenges of measuring very low levels of straylight and how these drive the breadboard and test facility design. We discuss the test and analysis procedures developed to ensure a representative, complete characterisation of the instrument’s straylight response.
Metis/Solar Orbiter polarimetric visible light channel calibration
Author(s):
M. Casti;
S. Fineschi;
G. Capobianco;
M. Romoli;
E. Antonucci;
G. Nicolini;
G. Naletto;
P. Nicolosi;
D. Spadaro;
V. Andretta;
M. Castronuovo;
G. Massone;
R. Susino;
V. Da Deppo;
F. Frassetto;
F. Landini;
M. Pancrazzi;
L. Teriaca;
M. Uslenghi
Show Abstract
Metis is the solar coronagraph of the ESA mission Solar Orbiter. For the first time, Metis will acquire simultaneous images of the solar corona in linearly polarized, broadband visible light (580-640 nm) and in the narrow-band HI Ly-α line (121.6 nm). The visible light path includes a polarimeter, designed to observe and analyse the K-corona linearly polarized by Thomson scattering. The polarimeter comprises a liquid crystal Polarization Modulation Package (PMP) together with a quarter-wave retarder and a linear polarizer. The Metis PMP consists of two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with their fast axis parallel with respect to each other and a pre-tilted angle of the molecules in opposite direction. This configuration results in an instrumental wide field of view (±7°). The LCVRs provide an electro-optical modulation of the input polarized light by applying an electric field to the liquid crystal molecules inside the cells. A given optical retardance can be induced in the LCVRs by selecting a suitable voltage value. This paper reports the polarimetric characterization of the Visible-light channel for the Metis/Solar Orbiter coronagraph. The retardance-to-voltage calibration of the electro-optical polarimeter was characterized over the entire field of view of the coronagraph yielding a complete “polarimetric flat-field” of the Metis Visible-light channel.
Teledyne’s high performance infrared detectors for Space missions
Author(s):
Paul Jerram;
James Beletic
Show Abstract
Teledyne is one of the world’s leaders in the provision of infrared sensors for Earth science, planetary science, and astronomy. This paper presents Teledyne’s focal plane array technologies that provide high performance for space missions, with sections on substrate-removed HgCdTe (that provides simultaneous visible / IR detection) and fully depleted HgCdTe (that enables detectors to be operated at significantly increased temperatures). We give examples of the image sensors provided for Euclid, WFIRST, AVIRIS-NG, ECOSTRESS, and NEOCam.
Status of space activity and science detectors development at Sofradir
Author(s):
Bruno Fieque;
Philippe Chorier;
Adrien Lamoure;
Olivier Offranc
Show Abstract
SOFRADIR is one of the main companies involved in the development and manufacturing of infrared detectors for space applications leading to many space studies and programs from visible up to VLWIR spectral ranges. Numerous programs are currently running for different kinds of missions: meteorology (MTG), Copernicus with the Sentinel detectors series, Metop-SG system (3MI, Sentinel-5 and Metimage), Mars exploration (Exomars), moon exploration (Chandrayaan mission with Indian space agency)…
Apart from these programs, the development of scientific missions is increasing. In particular, for the last 5 years, Sofradir and CEA-LETI have worked on specific detectors in SWIR bands to address these needs. The ALFA detector development in progress is the result of these developments. It is expected to propose the first generation of this detector in 2019 for upcoming scientific mission and / or ground universe exploration.
In this paper, an overview of space activity at Sofradir with the main space programs and developments will be described, followed by a description of very large detector developments made for science.
VIS/SWIR IR detectors for space applications at AIM: models and qualification status
Author(s):
H. Höhnemann;
S. Hanna;
A. Sieck;
R. Thöt;
M. Benecke;
J. Wendler;
A. Weber;
D. Hübner;
H. Figgemeier;
R. Breiter;
W. Gross
Show Abstract
AIM has developed IR modules including the FPAs for a wide range of applications. For SWIR applications FPAs based on liquid phase epitaxy (LPE) are available. These devices having different array sizes and are usable in a wide range of hyperspectral imaging applications. Silicon readout circuits provide various integration and readout modes including specific functions for spectral imaging applications.
An important advantage of MCT based detectors is the tunable band gap. The spectral sensitivity of MCT detectors can be engineered to cover the extended SWIR spectral region up to 2.5μm without compromising in performance.
AIM developed and released the technology option to extend the spectral sensitivity of its SWIR modules also into the VIS. This has been successfully demonstrated for different FPA designs. A short overview is given in tis paper.
AIM has qualified this VIS technology option based on a 1024x256 FPA capable for extended hyperspectral applications. Within this paper the test approach and the results will be presented.
Progress in thin film coating on space IR detectors
Author(s):
L. Macé;
E. H. Oubensaid;
F. Pradal;
R. Lhuillier;
H. Leplan;
O. Gauthier-Lafaye;
A. Monmayrant
Show Abstract
Improvements as well as new functionalities can be implemented in IR sensors by depositing a stack of thin film layers on top their surface. For this purpose, Safran Reosc has developed and qualified various processes, from conventional deposition methods to planar structuration approaches. In this article, the usefulness of thin film AR coatings are addressed and the latest results obtained on projects like Sentinel-5 and Microcarb IR focal planes are presented and discussed. We also address our progress in pixelization of the coating by structuration of these optical layers. Eventually, the most recent developments of sub-lambda photonic filtering structures are discussed.
Optical switch matrix development for new concepts of photonic based flexible telecom payloads
Author(s):
Karen Ravel;
Charlie Koechlin;
Eddie Prevost;
Thierry Bomer;
Romain Poirier;
Laurence Tonck;
Guillaume Guinde;
Matthieu Beaumel;
Nick Parsons;
Michael Enrico;
Sean Barker
Show Abstract
The next generation of telecom satellite makes the industry facing a technological rupture to reach high data throughput up to 1 terabit/s, while making communications links reconfigurable during all mission phases. That is why the introduction of optical communication technologies like laser links or photonic payloads in telecom satellites is foreseen to revolutionize the space telecom market. Hence the groundbreaking photonic payload will enable reaching the increasing demand of debit and flexibility thanks to miniaturization. In such photonic payload, the proposed optical switch will provide both the added value of optical fiber and new flexibility, redundancy and adaptability functions. Sodern, a recognized space equipment provider is presently spatializing the DirectLight® 1,55 μm Optical Switching Technology from HUBER+SUHNER Polatis Ltd (UK), the worldwide leader in optical switch technology for ground telecommunications and datacenter networks.
This paper focuses on the development activities of Sodern and Polatis on their Space Optical Switch development both for GEO 1 terabit/s high reliability and for low cost LEO constellations. An overview of the technology evaluations and design studies as well as of breadboard performance and environmental testing will be presented. Finally Sodern will explain the product development roadmap including the upcoming EQM.
High-performance DFB laser module for space applications: the FP7 HiPPO achievements from chip fabrication to system validation
Author(s):
M. Faugeron;
B. Benazet;
A. Maho;
A. Le Kernec;
M. Sotom;
F. Van Dijk;
J. P. Le Goëc;
O. Parillaud;
L. Stampoulidis;
P. Henderson;
S. Snowden;
E. Kehayas
Show Abstract
This article reports the development of 200-mW 1.55-μm DFB laser module with RIN below -162 dB/Hz which are well suited for microwave photonics or free space optical communication applications. Specific design has allowed reaching high power (>300 mW), low noise and high spectral purity laser chip. The chip has been packaged in Butterfly module optimized for reducing the module power consumption. DFB laser module system validations have been done on three laboratory test-beds representative of target applications, namely high-frequency optical LO distribution, photonic RF frequency conversion, and free space optical communication links.
Packaging Improvement of LiNbO3 modulators and Space evaluation results
Author(s):
A. Mottet;
S. Jillard;
J. Hauden;
N. Grossard;
H. Porte;
J. Tchahame;
D. Veyrié;
O. Gilard
Show Abstract
This paper presents the technical solutions implemented with the support of the French Space Agency (CNES) to design and manufacture hermetic Lithium Niobate (LiNbO3: LN) modulators, in the framework of a Research & Technology (R&T) project [1]. There is also presented some identified space-compatible raw materials that constitute modulators and some relevant results of a space evaluation program realized on about fifteen of these hermetic modulators (including hermeticity tests, mechanical tests and climatic tests).
PLATO FPA. focal plane assembly of PLATO instrument
Author(s):
J. Moreno;
E. Vielba;
A. Manjón;
A. Motos;
E. Vázquez;
E. Rodríguez;
D. Saez;
M. Sengl;
J. Fernández;
G. Campos;
D. Muñoz;
M. Mas;
A. Balado;
G. Ramos;
C. Cerruti;
M. Pajas;
I. Catalán;
M. A. Alcacera;
A. Valverde;
P. Pflueger;
I. Vera
Show Abstract
This paper describes the thermo-mechanical design of the Focal Plane Assembly (FPA) of the PLAnetary Transits and Oscillations of stars (PLATO) Instrument, developed by INTA and LIDAX. This is an ESA program with OHB as industry prime. In terms of assembly, alignment, and operational stability very demanding needs are required by a huge focal plane composed of four CCDs to assure the proper performance. This is translated into a complex thermomechanical design which shall be also focused on the correct production approach of the main parts involved, including several processes, and taking into account the number of cameras, and therefore Focal Plane Assemblies, to be produced (26). Part of these challenges, and their associated risks, are mitigated by means of the development of a totally representative prototype, which is currently finishing the integration phase and facing the test campaign.
Innovative focal plane segmentation for high-resolution planetary observation
Author(s):
Grégoire Hein;
Marc Ferrari;
Nicolas Tetaz
Show Abstract
As of today, Earth and planetary high-resolution observations rely on linear focal plane arrays used in TDI mode to acquire images delivered by the telescope. To both reach high angular resolution and keep a large field-of-view, homothetic imaging systems as used in Pleiades satellites or Mars Reconnaissance Orbiter [1] would lead to prohibitive linear focal plane dimensions. Reducing this parameter would therefore allow for a significant decrease in the size of space optical systems. The solution described in this paper intends to optically reduce this dimension by segmenting the linear FOV into smaller sub-fields that are stacked on a CMOS TDI sensor. It is therefore possible to drastically reduce the linear size of the array, at the expense however of a small increase in terms of complexity of the optical system.
Optical design and performance analysis of a CubeSat-sized limb sounder utilizing a spatial heterodyne spectrometer for the measurement of mesospheric temperature
Author(s):
Martin Kaufmann;
Friedhelm Olschewski;
Klaus Mantel;
Oliver Wroblowski;
Jilin Liu;
Michael Deiml;
Qiuyu Chen;
Ulrike Lembke;
Saroj Mihalik;
Brian Solheim;
Gordon Shepherd;
Ralf Koppmann;
Martin Riese
Show Abstract
A highly miniaturized limb sounder for the observation of the O2 A-band to derive temperatures in the mesosphere and lower thermosphere is presented. The instrument consists of a monolithic spatial heterodyne spectrometer, which is able to resolve the rotational structure of that band. The SHS operates at a Littrow wavelength of 762 nm with a resolving power in the order of 10.000. Complemented by a front optics with an acceptance angle of less than ±1 degree and a detector optics, the entire optical system fits into a volume of about 1.5 liters. This allows this instrument to be flown on a three or six unit CubeSat. In this paper, we introduce the optical design and computer simulations on the expected performance of the instrument. The laboratory characterization of a prototype instrument, which has been built on university level, and the lessons learned are discussed.
NanoCarb part 2: performance assessment for total column CO2 monitoring from a nano-satellite
Author(s):
Silvère Gousset;
Laurence Croizé;
Etienne Le Coarer;
Yann Ferrec;
Laure Brooker
Show Abstract
NanoCarb is an innovative Fourier Transform imaging spectrometer dedicated to the measurement of CO2 and CH4. Both its unusual optical principle and sampling strategy allows to reach a compact design, ideal for small satellite constellation as investigated by the European project SCARBO. The NanoCarb performance assessment as well as a proof of concept are required in this framework. A strategy of design is developed to optimize the performances and reach the sensitivity target of the space mission, demonstrating the potential of the concept without drastic complexity gain. A preliminary bias mitigation in the retrieval strategy is presented concerning water for CO2 measurement, illustrating the efficiency and the flexibility of the NanoCarb partial interferogram sampling technic. The presented design reaches a random error sub-ppm for CO2 and sub-10ppb for CH4, considering a 128 to 192 km swath, respectively, for 2 or 3 km of resolution at ground. A full mitigation of the water bias is performed on CO2 band thanks to partial interferograms.
Detector development activities supported by the European Space Agency
Author(s):
Heidrun Weber;
Nick Nelms;
Kyriaki Minoglou;
Alessandra Ciapponi;
Sarah Wittig;
Bruno Leone
Show Abstract
Detectors play a crucial role for the instrument design and the achievable instrument performance. The wavebands of interest for remote sensing are the visible and the infrared. Therefore, the European Space Agency has a strong interest in the performance enhancement of detector arrays in those spectral ranges. The Agency follows a continuous development strategy to enhance the capabilities for future Earth observation and astronomy missions. This paper presents the technical and planning status of these detector technology development activities.
HgCdTe APDs detector developments at CEA/Leti for atmospheric lidar and free space optical communications
Author(s):
Johan Rothman;
Pierre Bleuet;
Julie Abergel;
Sylvain Gout;
Gilles Lasfargues;
Lydie Mathieu;
Jean-Alain Nicolas;
Jean-Pierre Rostaing;
Stephanie Huet;
Pierre Castelein;
Kévin Aubaret;
Olivier Saint-Pé
Show Abstract
HgCdTe APD detector modules telecommunication are developed at CEA/Leti for atmospheric LIDAR and free space optical (FSO). The development is driven by the design and manufacture of generic sub-assemblies that can be adapted in each detector module to meet the specific detector requirements of each application. The optimization of such subassemblies is detailed in perspective of the challenges that are set by the specifications for detector modules currently developed for atmospheric LIDAR, in the scope of an R&T CNES project for Airbus and an H2020 project HOLDON, and FSO, in the scope of an ESA project and in collaboration with Mynaric Lasercom GmbH. Two detector modules have recently been delivered to Airbus DS for extensive LIDAR simulation tests. Initial characterization of these modules shows that the input noise, NEP=10-15fW/√Hz (5 photons rms) have been reduced by a factor three compared to previously developed large area detectors although the bandwidth have been increased to 180 MHz in order to respond to the requirements of high spatial depth resolution. The temporal remanence was 10-4 at 200 ns after the detection of short light impulse, which is compatible with demanding LIDAR applications such as bathymetric profiling.
Low flux NGP characterisation for microcarb application
Author(s):
A. Bardoux;
A. Ledot;
L. Tauziede;
G. Chevallier
Show Abstract
CNES (French Space Agency) is developing a microsatellite to monitor and characterize CO
2 surface fluxes, that is, the exchanges between sources (natural or anthropogenic) and sinks (atmosphere, ocean, land and vegetation). A better assessment of carbon fluxes is necessary to improve our understanding of the mechanisms governing the exchanges between sources and sinks, their seasonal variability, and their evolution in response to climate change. Values of CO
2 concentrations need to be measured with high precision, of the order of 1 ppm (to be compared with the CO
2 concentration of 400 ppm) to be able to estimate gradients which amounts to a few ppm.
The instrument on board MicroCarb is an infrared passive spectrometer operating in four wavelengths using an echelle grating (dispersive element) to achieve spectral dispersion. The spectral bands cover vissible end Short Wave infrared domain, from 764 μm to 2,075 μm.
The selected detector is the NGP (new Generation Panchromatic) manufactured by Sofradir, supplied with a specific AntiReflection coating in order to optimize both sensitivity and stray light.
The high accuracy level of the mission requires a high performance detector, operating at low incident flux, and whose imperfections will be very well known, in order to be corrected. The detector non-linearity is the main performance that has to be calibrated in order to allow the overall scientific objectives. CNES has developed a specific test bench in order to assess this performance.
This paper describes in detail
- The test bench constitution
- The test bench calibration
- The first detector measurements
Fire detection from LEO: trade-offs for selection of spectral bands and a wide-swath optical design using MWIR and visible bands
Author(s):
Dan Lobb;
Rachel Bird;
Martin Wooster;
Amanda Regan
Show Abstract
The paper relates to design of a sensor, operating on a platform Low-Earth Orbit, that will detect and measure actively burning fires on Earth surface. Trade-offs for selection of spectral bands are covered, concentrating on options using cooled detectors. A system using only two mid-wave infrared (MWIR) bands is shown to be viable; it will have significant cost advantages compared with a system that also uses long-wave infrared (LWIR), since it requires smaller optics for spatial resolution at the diffraction limit, and less-extreme detector cooling. Imaging in at least one visible band will allow identification of false detections due to sun glint, so that small fires can be positively identified in sunlight.
A proposed sensor will operate in pushbroom mode. The design uses a single area-array MWIR detector with a 1280 x 1024 element format. A swath approaching 10,000 pixels wide is provided by sub-dividing the swath between 8 telescopes that image onto separate sets of strip filters and detector rows. This allows a total swath width approaching 1000km wide to be scanned at 100m ground sample distance (GSD). The relatively small GSD, and use of multiple detector rows for each swath-section and band, will provide a capability for detection of small fires, with radiant powers in the range 0.5 to 1.0 MW. Wide swath will maximize statistical data collected by the sensor, and will also be of potential interest for development of constellation providing global fire monitoring.
Design, calibration, and on-orbit testing of the geostationary lightning mapper on the GOES-R series weather satellite
Author(s):
Samantha Edgington;
Clemens Tillier;
Mark Anderson
Show Abstract
The GOES-R series is the latest in a long line of American geostationary weather satellites operated by the National Oceanic and Atmospheric Administration (NOAA). The two Geostationary Lightning Mapper (GLM) instruments currently operating on the GOES-16 and GOES-17 satellites give NOAA a unique new capability to map in-cloud and cloud-to-ground lightning flashes across the entire hemisphere within seconds of their occurrence. GLM enables improved warning times for severe weather events, decreased false alarms, persistent coverage over wide geographical areas without sampling bias, and long-term monitoring of trends linked to the changing climate.
Viewed from space, emissions from lightning appear as a series of brief (~500 μs) optical pulses diffused through clouds over scales of tens to thousands of km
2. A significant portion of the emitted optical radiation is in the form of emission lines, including a prominent neutral atomic oxygen triplet whose emission lines are near 777 nm. GLM discriminates lightning flashes from the bright sunlit cloud background by taking advantage of the spatial, temporal, and spectral characteristics of the optical signature of lightning.
This paper describes key design drivers in the development of GLM, methods used to calibrate the instrument, and lessons learned from on-orbit testing. We discuss optimization of the entire signal chain, from the telescope optics to the ground processing algorithms.
SEOSAT/Ingenio: a high-resolution land imaging mission
Author(s):
A. Marini;
F. Reina;
A. Popescu;
C. Castaño;
I. Cabeza;
C. Santos;
C. Miravet;
D. Zorita;
Y. Delclaud
Show Abstract
SEOSAT/Ingenio (Spanish Earth Observation SATellite) is a high-spatial-resolution optical mission procured by the European Space Agency on behalf of and funded through the Spanish program authority CDTI. The Seosat/Ingenio mission is part of the Spanish Earth Observation National Program for Satellites (PNOTS). The mission is devoted to provide land and coastal zone optical images (panchromatic and multispectral) for applications in cartography, land use and mapping, urban management, costal management, agriculture monitoring, precision agriculture, water management, environmental monitoring, risk management and security and is a potential contributor to the European Copernicus program.
The SEOSAT/Ingenio satellite will operate from a polar-heliosynchronous orbit at 670 km of altitude and has an imaging capability up to 2.5 Mkm
2 per day, with world-wide accessibility in less than 3 days and a design lifetime of 7 years. The satellite is based on an Astrobus-M platform architecture weighing about 800 kg and with 580 W installed power and is compatible with a launch with Vega.
The Primary Payload is a push-broom imager, observing simultaneously in a Panchromatic band with 2.5 m resolution and in 4 multispectral bands (B,G,R and NIR) with 10 m resolution, over a swath of 55 km. Bands are co-registered at 1/10 of the pixel and geo-located at subpixel level in post-processing. The Optical design relies on two Korsch on-axis 250 mm aperture telescopes with intermediate imaging plane, in-field spectral separation and staggered-detectors focal planes. The detection system is based on CCD’s (with TDI operation for the PAN) and has MS color filters with direct deposition of the pass bands and masks on a single substrate.
The Satellite flight model is undergoing final integration and testing after final characterization and calibration of the Primary Payload . The SEOSAT satellite is expected to be ready for launch by end 2019.
SIMBIOSYS-STC ready for launch: a technical recap
Author(s):
Emanuele Simioni;
Vania Da Deppo;
Cristina Re;
Maria Teresa Capria;
Giampiero Naletto;
Gianfranco Forlani;
Leonardo Tommasi;
Michele Dami;
Donato Borrelli;
Iacopo Ficai Veltroni;
Matteo Massironi;
Alessandra Slemer;
Raffaele Mugnuolo;
Francesco Longo;
Gabriele Cremonese
Show Abstract
BepiColombo is the first ambitious, multi-spacecraft mission of ESA/JAXA to Mercury. It will be launched in October 2018 from Kourou, French Guiana, starting a 7-year journey, which will bring its modules to the innermost planet of the solar system.
The Stereo Camera (STC) is part of the SIMBIO-SYS instrument, the Italian suite for imaging in visible and near infrared which is mounted on the BepiColombo European module, i.e. the Mercury Planetary Orbiter (MPO). STC represents the first push-frame stereo camera on board of an ESA satellite and its main objective is the global three-dimensional reconstruction of the Mercury surface.
The harsh environment around Mercury and the new stereo acquisition concept adopted for STC pushed our team to conceive a new design for the camera and to carry out specific calibration activities to validate its photogrammetric performance. Two divergent optical channels converging the collected light onto a unique optical head, consisting in an off-axis telescope, will provide images of the surface with an on-ground resolution at periherm of 58 m and a vertical precision of 80 m.
The observation strategies and operation procedures have been designed to optimize the data-volume and guarantee the global mapping considering the MPO orbit.
Multiple calibrations have been performed on-ground and they will be repeated during the mission to improve the instrument performance: the dark side of the planet will be exploited for dark calibrations while stellar fields will be acquired to perform geometrical and radiometric calibrations.
Broadband antireflection coatings for visible and infrared ranges
Author(s):
F. Lemarquis;
T. Begou;
J. Ruscica;
D. Turover;
J. Lumeau
Show Abstract
Antireflection coatings are among the most common and spread optical coatings that are used in every optical system in order to decrease losses and prevent shadow images. For space applications, they are critical elements which specifications will highly influence the overall optical systems performances. Despite the very wide range of developments that have been carried out over the past thirty years, the production of broadband antireflection coatings for visible and infrared ranges remains a challenge. In this paper, we will present some recent results based on thin film technology for the production of antireflection coatings dedicated to visible, near-IR and mid-IR spectral ranges. We will first present broadband antireflection coatings for [400-1100] nm spectral range We will present two type of coatings, one for normal and one for oblique incidence. Experimental demonstration by plasma assisted reactive magnetron sputtering using a Bühler HELIOS machine will be presented. We will then show antireflection coatings covering the [1.5-15] μm range. Experimental demonstration and limitation will be presented.
Development of linear variable filter and black coatings by PARMS technology for FLORIS HR focal plane array of FLEX mission
Author(s):
Thomas Weber;
Marc Lappschies;
Stefan Jakobs;
Marco Meini;
Riccardo Gabrieli;
Matteo Taccola
Show Abstract
Beside homogeneous filter coatings a coating can also be applied with a linear gradient. Linear gradient or linear variable filters show a gradient of a band edge or central wavelength depending on the filter type in spectral direction and they are homogeneous in spatial direction. In this paper, we present a linear variable narrow band pass filter with full width half maximum of about 8 nm and a transmittance of more than 98% in the wavelength range of 670 nm to 780 nm. The target for the gradient is 3.3. nm/mm. Due to the need of transmittance filter and AR coating are manufactured by means of Plasma Enhanced Magnetron Sputtering (PARMS). Additionally, the linear variable filter for FLEX mission requires a black mask to separate between HR1 and HR2 channel. This mask is also applied by OBJ by means of the PARMS process and a Ti based layer stack. Here, a reflectance of <1.5% in the range of 400 nm to 800 nm can be demonstrated. The definition of black mask was done by means of photolithography.
Advances in IBS Coatings for space applications on the topics of curved surfaces and laser damage
Author(s):
T. Böntgen;
T. Alig;
I. Balasa;
L. Jensen;
D. Ristau
Show Abstract
IBS Coatings are a good candidate for high performance applications. They are hard, dense, exhibit a small thermal shift, and have the best scattering and surface roughness performance of the various coating technologies. In addition, they feature a highly stable refractive index for the coated materials allowing the production of complex coatings. Because of their high density and resistance towards high energy radiation IBS coatings are also well suited for space applications. For high power laser applications, the vacuum stable damage threshold and low defect concentration qualify especially reactive ion beam sputtering as a suitable deposition method for space applications.
In the paper, results on coating activities using the IBS process are discussed in respect to two aspects. One is the adaption of the IBS to strongly curved surfaces like lenses exemplified by the FM lenses for the Copernicus Sentinel-4 mission. The other is a study to increase the laser-induced damage threshold for future LIDAR systems. This is accomplished by eliminating nano-scaled particles that act as damage precursors during laser radiation.
Uniformity and wavefront control of optical filters
Author(s):
Michael Vergöhl;
Chris Britze;
Stefan Bruns;
Andreas Pflug;
Jennifer Zimara;
Bernd Schäfer;
Klaus Mann;
Volker Kirschner
Show Abstract
The present paper addresses uniformity effects in demanding dielectric optical coatings. The origins of spectral resonant wavefront errors (WFE) induced by non-uniformities in complex dielectric filters are investigated in detail. The coating is a broad-band beamsplitter with a high reflectance between 400 and 900 nm and a high transmittance between 920 and 2300nm. The WFE can significantly be reduced with an optimized design. A new setup based on Hartmann-Shack sensors measures the spectrally dependent WFE in the visual spectral range. The paper presents a method for referencing the measured data. The experimental WFE maps obtained by spectral Hartmann-Shack measurements agree well with the expected spectra taken from spectral photometric measurements and the coating design. The paper also addresses coatings on curved surfaces. A band pass filter centered at 670 nm on the convex side of a lens was developed. Using a combination of a sub-rotation and special uniformity masks, a very low spectral shift of the passband position overall the lens surface could be demonstrated. The deposition concept and mask design, respectively, are developed via simulation studies based on a simulation approach shown in [10]. Extension of the model framework by plasma simulation and a concept for computing deposition profiles on moving 3D substrates was required for solving the problem.
Towards a tilt-to-length coupling calibration on the GRACE follow-on laser ranging instrument
Author(s):
H. Wegener
Show Abstract
The Laser Ranging Instrument (LRI) measures the biased range between the two GRACE Follow-On spacecraft (launched in May 2018) using laser interferometry. It is the first of its type and serves as a technology demonstrator. Here we present the working principle and a brief report on the first turn-on of the instrument. In particular, we will discuss the laser link acquisition and possible methods of calibrating Tilt-to-Length coupling.
Laser metrology concept consolidation for NGGM
Author(s):
K. Nicklaus;
S. Cesare;
L. Massotti;
L. Bonino;
S. Mottini;
M. Pisani;
P. Silvestrin
Show Abstract
Measurement of the static and temporal variation of Earth’s gravity field yields important information on water storage, seasonal and sub-seasonal water cycles, their impact on water levels and delivers key data to Earth’s climate models. The satellite mission GOCE (ESA) and GRACE (US-GER) resulted in in a significant improvement on our understanding of the system Earth. On GRACE and GRACE Follow-On two satellites are following each other on the same orbit with approx. 200 km distance to each other. A microwave inter-satellite ranging system measures the variation of the intersatellite distance from which the gravity field is derived. In addition, on GRACE Follow-On, which has been launched May 22nd 2018, a laser interferometer is added as an experiment to demonstrate the capability of this system to improve the ranging accuracy by at least one order of magnitude. To significantly improve the gravity field measurement accuracy, ESA is investigating the concept of a ‘Next generation gravity mission’ (NGGM), consisting of two pairs of satellites and a laser interferometer as the sole inter-satellite ranging system. Based on the heritage of the development of the laser ranging interferometer for GRACE Follow-On and the former and ongoing studies for NGGM, several concepts for the laser metrology instrument (LMI) for NGGM, namely the on- and off-axis variants of the transponder and the retroreflector concept have been investigated in detail with respect to their application for an inter-satellite distance of approx. 100 km. This paper presents the results of the detailed tradeoff between different concepts, including laser link acquisition, ranging noise contributors, instrument performance analyses, technology readiness levels of the individual instrument units and an instrument reliability assessment.
Optical metrology terminal for satellite-to-satellite laser ranging
Author(s):
Oliver Mandel;
Michael Chwalla;
Thilo Schuldt;
Jasper Krauser;
Dennis Weise;
Claus Braxmaier
Show Abstract
Interferometric laser ranging is an enabling technology for high-precision satellite-to-satellite tracking within the context of earth observation, gravitational wave detection, or formation flying. In orbit, the measurement system is affected by environmental influences, particularly satellite attitude jitter and temperature fluctuations, demanding an instrument design, which has a high level of thermal stability and is insensitive to rotations around the satellite's center of mass. Different design approaches for a heterodyne dynamic laser ranging instrument have been combined to a new improved design concept that involves the inherent beam tracking capabilities of a retroreflector into a mono-axial configuration with nanometer accuracy. In order to facilitate the accommodation onboard a future satellite mission, the design allows for a continuously adjustable flexible phase center position. To cover large inter-spacecraft distances, the instrument design comprises an active transponder system, featuring a two-dimensional beam steering mechanism to align a local, strong laser to the (weak) input beam without affecting the measurement path.
To this end, a dynamic laser ranging instrument is presented, which has compact dimensions and is fully integrated on a single Zerodur baseplate. The instrument performance will be evaluated in a dedicated test setup providing a flat-top beam simulating the laser beam received from a distant spacecraft, including a beam steering subsystem, which allows for monitoring of pathlength variations when the angle of incidence at the optical instrument is changing.
Novel satellite positioning system using acousto-optic deflector
Author(s):
Mitsuru Musha;
Kei Akami;
Aru Suemasa
Show Abstract
Space gravitational wave detector in Japan named DECIGO is equilateral triangle-shaped laser interferometer with the arm length of 1000 km. For initial alignment and keeping formation of DECIGO, we propose novel satellite positioning system. Our system consists of a single-mode laser, acousto-optic deflectors (AOD) and a frequency counter. The diffraction beam from AOD deflects with the deflection angle which is proportional to the modulation frequency of AOD. The modulation frequency is swept to scan the angle of the deflected beam, and, at the remote end, a photo detector derives its position from the detected modulation frequency of the scanned deflected beam. Compared with the conventional optical method, our system is compact and has no moving elements, and the angle resolution of our system depends on not the optical diffraction limit but the resolution of frequency counting. In the current paper, we present the principle and the preliminary results of our system.
Spaceflex onboard digital transparent processor: a new generation of DTP with optical digital interconnects
Author(s):
N. Venet;
V. Enjolras;
C. Nicolas;
P. Voisin
Show Abstract
As high-speed digital signal processing has become a reality taking an increasing place in telecom satellite payloads for today, Thales Alenia Space has introduced the most advanced and disruptive technologies in his new generation of onboard digital transparent processor (DTP). DTP namely Spaceflex is an advanced repeater sub-systems having analogueto- digital (ADC) and digital-to-analogue (DAC) channelizers on their input and output accesses and making extensive use of digital processing to support channel routing with fine bandwidth granularity.
The mechanical architecture of such advanced digital processor is based on input/output routing channel modules and switch modules interconnected together thanks to optical interconnect technology already implemented in a breadboard developed under the ESTEC contract Optical Inter-board Interconnects for High Throughput on-Board Processors (OI2) but showing higher performances requested by the application.
The optical interconnect is supported by optical transceiver, by optical connectors for inside and outside equipment interconnects, by optical cables and flexes. This optical interconnect solution is scalable to an overall throughput in excess of 15 Terabit/s with 150’s of optical links.
In the frame of this development, Thales Alenia Space has identified and tested 3 different optical transceivers working at high speed data rate higher than 10 Gbps, compatible with GEO and LEO environment whose reliability is compatible with a lifetime of 15 years.
The paper will present in detail the tests on selected transceiver (radiation behaviour and temperature) as well as the overall architecture of such advanced digital on board processing equipment.
High-speed low-power and board-mountable optical transceivers for scalable & energy efficient advanced on‐board digital processors
Author(s):
L. Stampoulidis;
E. Kehayas;
M. Karppinen;
A. Tanskanen;
J. Ollila;
J. Gustavsson;
A. Larsson;
L. Grüner-Nielsen;
Christian Larsen;
M. Sotom;
Anaelle Maho;
Mickael Faugeron;
N. Venet;
M. Ko;
P. Ostrovskyy;
D. Kissinger;
R. Safaisini;
R. King;
I. McKenzie;
J. B. Gonzalez
Show Abstract
We present the development and verification testing of a high speed multimode, multicore transceiver technology for intra-satellite optical interconnects. We report the fabrication and functional testing of opto-parts including 25 Gb/s 850 nm VCSEL/PD as well as the verification testing of the VCSELs against radiation and lifetime performance. In addition we report the development and evaluation testing of a multi-core cable assembly that was fabricated and mated with MiniAVIM multi-core connectors to develop hi-rel multi-core optical patchcords for pigtailing the transceiver modules. The fiber optic, electronic and opto-parts were used to assemble the first ever fully packaged and pigtailed, six-core optical transceiver prototype module that operates at 25 Gb/s channel bit rate at an energy consumption of ∠4.5 mW/Gb/s.
Mass-reduction of high-speed spacecraft datalinks enabled by rugged photonic transceivers
Author(s):
R. T. Logan Jr.;
Davinder Basuita
Show Abstract
In this paper, we first review the advantages in mass, loss and bandwidth of fiber optic links compared to coax for the fiber-optic physical layer of high-speed digital datalinks on spacecraft. We then report the results of ongoing development of commercial-off-the-shelf photonic transceiver components designed to meet spacecraft physical layer fiber optic datalink requirements. Results are presented detailing the performance and reliability of photonic transceiver modules, as well as radiation exposure tests (gamma, neutrons, protons and heavy ions) for these modules. The results show that these modules meet or exceed many of the requirements of spacecraft applications, and indeed they are being considered for or deployed on various spaceflight applications.
Fiber optical flexible routing assembly (FOFRA)
Author(s):
T. S. Mjåland;
V. Henriksen;
K. S. Manshaia
Show Abstract
Stricter requirements for data transmission, such as harness weight, data bandwidth and attenuation, have caused a rising demand for fiber optical (FO) solutions in the space market. The market is in need of solutions that are able to accommodate a high number of fibers, be highly customizable and have a low assembly, integration and test (AIT) time.
In this context we present the development of the Fiber Optical Flexible Routing Assembly (FOFRA) under the ARTES 5.2 programme. The FOFRA is a thin and flexible optical circuit board that offers a protected layout environment for fibers in a systematic high-density pattern. Today, the FOFRAs are produced for jet fighters and other applications.
Routing a larger number of fibers is a time-consuming and meticulous task which requires an optimized systematic design with a high routing precision. A fiber optical routing machine has been developed together with a routing software for this application. It has been demonstrated that these tools can produce a large variety of FOFRAs regarding size, shape, material and fiber I/O interface. The FOFRAs can be manufactured using materials with good space experience. The MT-ferrule has been selected as the preferred interface option. Several variations of FOFRAs will be presented.
Measuring, modeling and removing optical straylight from venμs super spectral camera images
Author(s):
Philippe Gamet;
Sébastien Fourest;
Tuvia Sprecher;
Emmanuel Hillairet
Show Abstract
The Venμs Super Spectral Camera suffers from high level of optical straylight. The probable causes of this defect will be discussed. Two types of straylight are observed: local ghost is caused by scattering of optical surfaces of the instrument, and multiple reflexions between detector and filter or filter window, or lenses. Cross-talk ghost is constituted of light going through the filter of one band, and impacting another band on the same detector. It is caused by multiple reflexions between detectors and filter. The optical set-up used to evaluate the straylight patterns will be presented, and then, the approach used to characterize and model the observed phenomena will be detailed: Local straylight model is computed as a global system MTF that includes the local straylight. The assumption is made that the phenomenon can be modeled by a convolution, and that it is slowly variable within the instrument field of view. Crosstalk straylight is modeled from a pinhole, used to extract the impulsive response of the cross-talk. The cross-talk pattern is observed through the ghost generated by a saturated input signal. The cross-talk signals for all contributing bands of the same tri-detector are substracted from the image of each band. The performances of the correction model are presented: on the ground over test pattern images, and then in-flight during the image quality commissioning phase, over specific targets: moon, sand/water transitions.
Digital correction of residual straylight in FLEX images
Author(s):
S. Abdon;
D. Armand;
F. Laurent;
M. Barillot;
A. D'Ottavi;
P. Coppo;
E. De Luca;
R. Gabrieli;
M. Bouvet;
M. François;
M. Taccola
Show Abstract
The FLEX mission is defined to perform quantitative measurements of the solar induced vegetation fluorescence to monitor photosynthetic activity. The FLORIS payload is based on a spaceborne 3-channel grating spectrometer operating in the VNIR range.
The retrieval of the faint fluorescence signal from the acquired vegetation spectra is particularly sensitive to straylight.
As results, the straylight requirements on the FLORIS instrument are especially stringent.
For FLORIS a two-step straylight reduction process has been put in place by the Leonardo-Thales Alenia Space team to achieve this requirement. Careful instrument design and manufacturing are followed by digital processing of the raw instrument data.
In this paper we present the feasibility demonstration of the straylight digital correction process, based on simulation of the dedicated data processing and quantitative assessment of the residuals.
Post-processing correction of stray-light in space instruments: application to the 3MI earth observation instrument
Author(s):
L. Clermont;
C. Michel;
E. Mazy;
Y. Stockman
Show Abstract
Stray-light is a major concern in optical instruments and in particular for space missions. While many methods exist to reduce the stray-light by means of hardware optimization, manufacturing capabilities set the limit of the stray-light rejection that can be achieved. Hence, there are situations where the scientists that use the data require stray-light level lower than what hardware alone can reach. This is for example the case of the Metop-SG 3MI mission, which despite a well optimize instrument doesn’t reach as is the performance requirement. In such situations, it is necessary to add in the processing chain of the data a stray-light correction algorithm which further reduces the stray-light level. This paper discusses the algorithm implemented for 3MI.
Characterisation and performance verification results of the EarthCARE multi spectral imager VNS camera
Author(s):
Bryan T. G. de Goeij;
Dick de Bruijn;
Frits van der Knaap;
Hans Bol;
Wim Gielesen;
Andrew Bell;
Alan Matthews;
Mark Skipper;
Ben Hallett;
Maximilian Sauer;
Klaus-Werner Kruse;
Cornelius Haas;
Kotska Wallace;
Arnaud Heliere
Show Abstract
The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop the EarthCARE satellite mission with the fundamental objective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere.
A Cloud Profiling Radar (CPR), an Atmospheric LIDAR (ATLID), a Broadband Radiometer (BBR) and a Multi- Spectral Imager (MSI) constitute the payload complement of the EarthCARE satellite. The four instruments will provide synergistic data on cloud and aerosol vertical structure, horizontal cloud structure and radiant flux from sub-satellite cells. By acquiring images of the clouds and aerosol distribution, the MSI instrument will provide important contextual information in support of the radar and LIDAR data processing.
The MSI instrument itself consists of two camera units, the Thermal Infrared (TIR) camera and the Visible, Near- Infrared and Shortwave Infrared (VNS) camera, that are readout through a shared Front-End-Electronics (FEE) unit, all controlled by the Instrument Control unit (ICU).
The subject of this paper is the characterisation and performance verification results of the TNO designed and built Proto Flight Model (PFM) VNS camera in conjunction with the SSTL designed and built PFM FEE unit. This paper presents an overview of the characterisation and performance verification philosophy, followed by a more detailed presentation of several important measurements sets highlighted below.
Optical quality measurements (Modulation Transfer Function)
In order to measure the MTF of the VNS camera for several spatial frequencies simultaneously, a dedicated laboratory setup was built that provided the camera with block illumination patterns. Using Fourier analysis these optical block functions could be separated into their higher order components, resulting in acquisition of the MTF performance for several spatial frequencies concurrently.
Spectral Response measurements
For the VNS camera the spectral response was measured from 300nm up to 2400nm over the entire instrument swath of 360pixels. In order to perform this in an efficient manner a lock-in amplification setup was devised that included a “high” power pulsed tunable laser source, integrating spheres and monitoring detector.
In order to control pulse to pulse variations of the laser source and have a correct background correction, the 1kHz pulse frequency of the laser was further modulated by a several Hz chopper, resulting in spectral measurements with ~1% accuracy.
Straylight measurements
The straylight requirements for the VNS camera were specified as the maximum allowable amount of signal in an infinite dark area when illuminating the VNS camera with semi- infinite light source in an adjacent area. A dedicated tool was developed to simulate these (semi) infinite areas.
Radiometric characterization
For the VNS camera the required absolute radiometric accuracy was quite relaxed, 10% (5% goal). However, the interchannel radiometric accuracy between the VNS channels is required to be better than 1%. This last requirement could not be achieved by “standard” radiometric calibration methods and a calibration method was developed using the VNS camera itself in collaboration with an integrating sphere that was used in radiance and irradiance modes.After finalisation of the performance testing and calibration measurements the VNS camera was delivered to SSTL mid 2017 for further integration on the MSI Optical Bench Module and alignment with the TIR camera and other MSI subsystems by SSTL.
Wavefront control in the design of narrow-and broad-band optical coatings
Author(s):
Angela Piegari;
Anna Sytchkova;
Matteo Taccola
Show Abstract
The wavefront distortion induced by some optical coatings has often been underestimated with serious consequences in the performance of optical instruments. The typical approach to face such inconvenience consists in modifying the shape of the coated optics by compensating either the bending induced by stress or the geometrical thickness variations in nonuniform coatings. A relevant contribution to the wavefront distortion can also be given by the interference in the coating layers and a standard approach to overcome such problem is not available. In this work the wavefront deformation that is due to the spatial non-uniformity of thin-film optical coatings is analyzed, with the aim of identifying simple structures in which the influence of thickness non-uniformity on the wavefront shape is minimized. Some examples are reported especially for high-reflectance coatings.
Conceptual approaches to the study of efficient bandpass filter design for ultraviolet spaceborne instruments
Author(s):
U. Brauneck;
A. Hull;
R. Woodruff;
J. Sanchez;
D. Apitz;
T. Westerhoff
Show Abstract
In support of a spaceborne astrophysics instrument design, we have studied high UV filter efficiency and strong transmission blocking out to the end of Si response at 1100nm. For filters at wavelengths 297.5nm/338.5nm/379.5nm, these attributes are achieved with the combination of hard sputtered dielectric coatings on colored glass substrates. The filterglass substrates can be used to suppress ghost images caused by reflection at the exit face which is a common problem of all interference filter designs. Known disadvantages of filterglasses like solarization or autofluorescence are discussed and possible ways to mitigate are discussed. At two shorter wavelengths, 215.5nm and 256.5nm, metaldielectric Fabry-Perot stacks are applied on fused silica. Those traditional designs are advantageous due to their efficient blocking up to the mid IR range and economic low number of layers. We discuss the different design possibilities of metal-dielectric filters and ways to improve the steepness of the slopes. Resulting spectra are expressed.
Radiation testing of optical coatings: better testing with simulations
Author(s):
Jochen Kuhnhenn;
Michael Steffens;
Max Baum
Show Abstract
Radiation testing of thin optical coatings for space requires different approaches compared to bulk optical components or other material samples. In contrast to thicker samples, already particles of lower energy and thus lower range in the material will deposit high levels of dose in functional areas. In this paper we will discuss those differences and show ways to develop optimized test strategies.
Protected silver coatings for reflectors
Author(s):
Stefan Schwinde;
Mark Schürmann;
Ralph Schlegel;
Jan Kinast;
Reinhold J. Dorn;
Jean Louis Lizon;
Sebastien Tordo;
Norbert Kaiser
Show Abstract
For ground- and spaced based applications, Ag coated reflectors are indispensable because of their high reflectivity. The transport, assembling and storage of these reflectors takes a long time, before they are finally commissioned for the actual applications. To endure this period without a decrease of reflectivity, protective coatings with a final layer, which offers a high resistance to aqueous solutions and a low mechanical stress should be used. These criteria were taken into account for the selection of a final layer for a protected Ag-coating, which was applied for reflectors utilized in the CRIRES+- instrument (an IR spectrograph used at the VLT). Reactively sputtered Al2O3, SiO2 and Si3N4 layers were investigated with regard to these criteria. In aqueous (basic) solutions, the investigated Si3N4 layers are more stable than the SiO2 layers, and the SiO2 layers are more stable than the Al2O3 layers. This shows the influence of the intrinsic material properties. The mechanical stress of the sputtered layers depends on the deposition conditions and thus on the selected parameters. A Si3N4 layer with a high resistance to aqueous solutions also offers a low and stable mechanical stress. Therefore, the deposition-parameters which have been used for this layer were applied for sputtering the final layer of the protected Ag-coating for the reflectors.
JUICE navigation camera design
Author(s):
Frédéric Gorog;
Marie-Christine Arnolfo;
Salem Belmana;
Sebastien Dervaux;
Daniele Gherardi
Show Abstract
The Jupiter Icy Moon Explorer (JUICE) is an ESA mission whose aim is to study the Jovian system : Jupiter itself, its icy moons (Europa, Ganymede and Callisto) and the magnetosphere. For this challenging mission, Sodern was selected to provide the Navigation Camera (NavCam).
NavCam is a key instrument for the spacecraft navigation. During its lifetime JUICE does numerous fly-bys, however the delta V is limited by the available propellant in the spacecraft. To achieve such precise navigation in Jovian environment, ground based radiometric measurements are not sufficient, therefore it is paramount to measure the position of the Jupiter moons in-flight, with high accuracy,.
To achieve this measurement,
the NavCam assesses the position of the moon and stars in its field of view in an inertial reference frame. The combination of these two measurements gives the accurate position of each of Jupiter icy moons. The stars processing is similar to that of a star tracker and is performed inside the camera, whereas the moons detection is done on-ground from images captured by the camera. In addition to the above primary mission, the navigation camera will also be used by the spacecraft attitude control loop during close fly-bys in order to improve the spacecraft absolute pointing performance.
Jovian environment is particularly severe. The mission profile imposes considerable radiations constraints on the spacecraft, which are uncommon in typical space programs. Jupiter magnetic moment is the largest of the solar system (over 10,000 times higher than the Earth’s). It induces a high total dose exposure at electronic parts level (100krad), high number of Single Event Effects and internal charging effects. Furthermore, to achieve the best performances, the NavCam is mounted on the optical bench near sensitive instruments; so it must comply with stringent thermal control and magnetic cleanliness to avoid disturbances to the other instruments. Finally, the measurements of moons and stars in the same field of view induce complex optical design to mitigate stray light.
Star trackers and instrument experience paired with radiation and optical engineering know-how have put Sodern in the position to solve all these challenges. JUICE NavCam is at the moment at PDR stage, the paper describes the current features and the ongoing model activities.
UFSS (ultra fine sun sensor): CCD sun sensor with sub-arc second accuracy for the next solar observing satellite SOLAR-C
Author(s):
K. Tsuno;
S. Wada;
T. Ogawa;
T. Shimizu;
T. Hasegawa;
M. Kubo;
H. Murao;
S. Mizumoto;
S. Fujishima;
K. Toyonaga
Show Abstract
The Ultra Fine Sun Sensor (UFSS) on board the HINODE solar observing satellite is one of the most successful sun sensors. It is the linear CCD sun sensor with a special detection method using multiple slits, called the periodic reticle. The angular resolution of 0.14 arcsec in the noise equivalent angle (NEA) and 1 arcsec stability were achieved by the sensor head, of 1.2 kg weight. The concept of the detection method and processing algorithm of the Sun’s direction is described. The system is modeled and the dynamic response of the system is characterized by the first-order lag system. By utilizing this characteristic, a resolution improvement three times higher can be expected by adjusting the parameters with a small modification to the HINODE UFSS processing algorithm. The design for a new UFSS for the next generation solar observation satellite, SOLAR-C, shall include these modifications. The thermomechanical design is also reviewed to improve stability and a design policy is obtained.
Stray-light measurements on gratings: challenges and limitations
Author(s):
Dana Tomuta;
Volker Kirschner;
Matteo Taccola;
Micael Miranda;
Mathijs Arts
Show Abstract
The measurement of the bi-directional scatter distribution function (BSDF) is a well established process on reflective surfaces and largely also on transmissive optical elements. Such measurements are crucial and frequently used as input to assess the straylight performance of optical space instruments. The straylight performance of grating based spectrometers, such as used in Sentinel-5 or FLEX, is to a large extent driven by the grating itself. Thus, a BSDF characterization of gratings for such spectrometers is necessary early in the spectrometer development. However, performing such measurements on gratings turn out to be challenging for a number of reasons that will be presented and addressed in this paper. In this paper we address some of the challenges experienced when measuring BSDF at different wavelengths from UV up to SWIR for several type of gratings. Scatterometers are usually designed to measure the BSDF of a single flat optical surface. The particular form or construction of such gratings, for example transmissive gratings with at least two optical interfaces or gratings with optical power, requires a reconfiguration of the classical measurement set-up to minimise the errors in the BSDF characterization. Additionally, there is a difficulty of measuring the near-specular scatter of those components due to the inherent optical aberrations and potentially their curvature. The dispersive property of gratings imposes the use of a very stable and spectrally pure light source for the measurement. We suggest some strategies and configurations to mitigate the above-mentioned difficulties. Some BSDF measurements on curved and immersed gratings are presented in this paper for illustration.
On ground demonstrator of digital stabilization for high-resolution Earth observation time of delay integration imaging
Author(s):
S. Petit Poupart;
A. Materne;
C. Thiebaut;
J. M. Delvit;
C. Latry;
B. Mithieux
Show Abstract
CNES (French Space Agency) has developed a dedicated test bench to demonstrate its solution of digital stabilization for relaxing the AOCS constraints for high-resolution Earth observation Time of Delay Integration (TDI) imaging, based on a CNES patent1. TDI sensors are sensitive to high frequency attitude disturbances which may induce blurring effects when increasing TDI stages number and thus exposure time. A solution to relax the microvibration constraints (or no longer constrain the number of lines to be accumulated) is to compute, in real-time, the shift between each line and coregister them before summation. CNES solution includes a motion sensor dedicated to shift measurements, a fast realtime algorithm to compute the shift between two consecutives images delivered by the motion sensor, a multi-frame TDI sensor, and an algorithm to resample images delivered by sub-TDI devices using computed shifts, before summing them up in order to obtain the final image. The optimization study of the motion sensor and the performances of the gradientbased algorithm on these images have been already presented in a previous paper2. In this paper, we describe the dedicated test bench which contains each part of the presented chain and the obtained performances.
Advanced photonic payloads for broadband telecom satellites: Integration and tests of a representative repeater demonstrator
Author(s):
S. Roux;
T. Colombo;
M. Aveline;
M. Sotom;
B. Benazet;
M. Picq;
H. Leblond
Show Abstract
This paper reports the main achievements in the development of photonic RF payload solutions for telecommunication satellites based on a multiple-frequency conversion scheme. Representative models of photonic payload equipment, including photonic frequency generation assembly and frequency-converters, have been integrated and proven in a system environment. The end-to-end RF performance for various configurations and frequency plans were tested at ambient temperature. The test plan includes forward and return repeater configurations, with photonic frequency down-conversion from 30 to 20 GHz with up to 6-local oscillators in the case of a Ka-band multi-beam broadband mission. In addition, thermal tests were run over the [−5°C, +65°C] temperature range.
The end-to-end RF performances of the photonic repeater demonstrator were assessed in detail experimentally and compared to theoretical predictions. These results are a major step towards new payload solution with enhanced capacity and in-orbit re-configurability.
A flight demonstration photonic payload for up to Q/V-band implemented in a satellite Ka-band hosted payload aimed at broadband high throughput satellites
Author(s):
Miguel A. Piqueras;
Javier Martí;
Silvia Delgado;
Rob Singh;
Dan Beeder;
Robert Parish;
Ghislain Turgeon;
Antoni Castells;
Laurent Roux
Show Abstract
This paper provides a summary on the design, parameter allocations and testing of a Ka-band Flight Demonstration Photonic Payload aimed for payload solutions from Ku up to Q/V Band High Throughput Satellites (HTS) Systems. The paper describes the system and payload design overviews, identifies payload hardware, and summarizes key unit and payload performances for the Ka-Band Flight demonstration payload. The in-flight demonstration is now integrated as a hosted payload in a GEO communications satellite that is following spacecraft level integration and testing in preparation for launch. This hosted payload once on orbit will demonstrate the photonics technology and will perform an on orbit Ka-Band transmission/reception function with performance characterization and demonstration of operational capabilities.
Towards demonstration of photonic payload for telecom satellites
Author(s):
Javad Anzalchi;
Joyce Wong;
Thibaut Verges;
Olga Navasquillo;
Teresa Mengual;
Miguel A. Piqueras;
Eddie Prevost;
Karen Ravel;
Nick Parsons;
Michael Enrico;
Johan Bauwelink;
Michael Vanhoecke;
Antonello Vannucci;
Marcello Tienforti
Show Abstract
To address the challenges of the Digital Agenda for Europe (DAE) and also to remain in line with the evolution of terrestrial communications in a globally connected world, a major increase in telecoms satellites capacity is required in the near future.
With telecom satellites payloads based on traditional RF equipment, increase in capacity and flexibility has always translated into a more or less linear increase in equipment count, mass, power consumption and power dissipation.
The main challenge of next generation of High Throughput Satellites (HTS) is therefore to provide a ten-fold-increased capacity with enhanced flexibility while maintaining the overall satellite within a “launchable” volume and mass envelope [1], [2], [3]. Photonic is a very promising technology to overcome the above challenges. The ability of Photonic to handle high data rates and high frequencies, as well as enabling reduced size, mass, immunity to EMI and ease of harness routing (by using fibre-optic cables) is critical in this scenario.
SEEING: the SAFRAN EO payload for microsats
Author(s):
Roland Geyl;
Jacques Rodolfo;
Jean-Philippe Girault
Show Abstract
Safran is presenting its concept of optical payload for microsatellites combining high performances and extremely low SWAP factor. It is offering a high resolution of 1.5−m over 10x6,6 km2 area from the 500 km durable orbit. The concept is based on an advanced innovative diffraction limited optical system packaged in a unique very compact volume lower than 10U = 200x200x250 mm making it the ideal solution for 15-100 kg microsatellites. A maximum number of pixels are delivered to the end-user space imagery community thanks to 35 mm Full Frame sensors offering, as of today, 6600x4400 pixels. Panchro imagery and multispectral up to 8 bands 450 to 1000 nm can be offered thanks to 2D structured filters..
Far ultra-violet polarimeter by reflection for Pollux (LUVOIR)
Author(s):
Maëlle Le Gal;
Arturo López Ariste;
Coralie Neiner
Show Abstract
The ultra-violet (UV) high-resolution spectropolarimeter Pollux is being studied in Europe under CNES leadership for the LUVOIR space mission. LUVOIR is a projected 15−m telescope equipped with a suite of instruments proposed to NASA. Pollux will perform spectropolarimetric measurements from 90 to 400 nm with a resolution of 120000. The spectrograph will be divided in three channels, each with its own polarimeter: far UV (FUV, 90−124.5 nm), mid UV (MUV, 118.5−195 nm), and near UV (NUV, 190-390 nm). We present here our FUV prototype and our investigation to optimize this polarimeter (angle, materials, coating…).
Design study of a hosted Arctic imager for weather and climate monitoring in the polar regions
Author(s):
Peter Buschkamp;
Stephan Gulde;
Charlotte Bewick;
Patrick Tully Peacocke;
Paolo Sandri;
Frank te Hennepe
Show Abstract
A Hosted Arctic Imager (HAI) concept is currently being investigated as part of ESA’s Polaris program. HAI intends to fulfil the needs for providing weather and atmospheric services in the polar regions enabling e.g. near-real-time observations of Atmospheric Motion Vectors of the Arctic and Nordic regions, similar to the measurements offered by its Meteosat counterparts in GEO, such as SEVIRI on MSG and FCI on MTG. The compact hosted-payload multispectral imager operates from a High Elliptical Orbit in 12 spectral bands from 0.4μm to 13.3μm at a Ground Sampling Distance of 1-3km. The optical concepts employs a split design into a wavelength-optimized VIS and a (N)IR telescope, built as all-metal free-form optics, where a hole in the first mirror of the (N)IR telescope presents the entrance aperture of the VIS telescope. Our instrument design maximizes the re-use of heritage technology, e.g. for detectors, scanner, and calibration elements, in order to enable a low-risk fast-track development program.
Space flight-model multichannel photometer for spectral detection of stratospheric transient luminous events in Taranis mission
Author(s):
S. Gaillac;
D. Euzenne;
W. Glastre;
P. Maquet;
H. Philippe;
T. Farges;
K. Mathieu;
E. Bellouard;
D. Faye
Show Abstract
In 1990, scientists discovered and started studying the luminous events which occur above storms at altitudes of 20 to 100km. These Transient Luminous Events (TLE) are associated to high energy particle emissions like X rays, gamma rays… They cannot be easily observed from earth because of clouds and atmospheric absorption. Goal of Taranis satellite which will be launch in 2019 is to collect high resolution data on these TLE.
One of Taranis satellite instruments is a photometer which goals will be to measure emitted light in 4 different wavelength ranges and to distinguish TLE emission from lightning’s emission. Bertin Technology has been assigned the task to design, develop, integrate and validate this optical sensor.
The photometer aims at measuring very low light levels with a high signal to noise ratio and with a good uniformity all over an important field of view. These requirements lead to use high sensitivity detectors, special filtering systems in UV channel (180−220nm) and specific optical system to limit the loss of energy and to flatten the optical response over the field of view.
The development of the photometer was submitted to important environmental constraints: mass, available space, vibration, shocks, temperatures… Bertin’s challenge has been to take into account these strong environmental requirements which specific damping mechanical system working at low temperature. Final performances measured on the flying model are presented.
Black coatings for combined stray light and thermal passive management for the challenging environmental conditions of Solar Orbiter
Author(s):
Luca Montemurro;
Francesco Zanetti;
Antonia Simone;
Tiziano Schillaci;
Marco Castronuovo;
Dina Katsir;
Keren Shabtai
Show Abstract
In the context of ESA’s Cosmic Vision 2015-2025 scientific program, Solar Orbiter (SolO) represents the first M-class mission, currently under implementation for a launch planned in October 2018.
One of the SolO solar remote-sensing instruments is the Multi Element Telescope for Imaging and Spectroscopy (METIS), under development by an Italian consortium ATI composed by CGS and TAS-I. METIS is a coronagraph that will perform simultaneously broad-band imaging in visible light and narrow-band imaging in UV of the Sun corona with unprecedented spatial resolution.
The surfaces of several Ti-6Al-4V components of the METIS Optical Unit must have a very low reflectance in order to minimize straylight and therefore ACKTAR Magic Black
TM coating was specified. An example is represented by the internal surface of the Inverted External Occulter (IEO) - the front part of the instrument - which is exposed to the direct solar flux and experiences challenging environmental conditions. Qualification for 450°C was required whereas Acktar's Magic Black
TM qualified maximum temperature was 380°C.
A dedicated thermal-vacuum cycling test (100 total cycles, −120°C − 450°C) was conducted to qualify Magic Black
TM to quantify any performance degradation under these conditions:
• optical (reflectance)
• thermal (∝ and ε values) to allow calculation of the radiative heat transfer of the METIS parts during mission
• mechanical performances
The following success criteria were established:
• total reflectance at wavelengths of 400−1000nm <;5%
• degradation of absorptance ∝ and emissivity ε to be <10%
• surface resistivity <5 kΩ/square
Solar rejection window and narrow band pass filters for the Meteosat third generation lighting imager
Author(s):
C. Montcalm;
A. Badeen;
D. Burbidge;
R. Bruce;
G. Carlow;
J. Dane;
N. Firdawsi;
G. E. Laframboise;
A. M. Miles;
J.-P. Noel;
R. Rinfret;
B. T. Sullivan;
R. Bardazzi;
S. Lorenzini;
L. Giunti
Show Abstract
This paper presents the design, manufacture and characterization results of two optical interference filters to be used in the Lightning Imager (LI) optical head on the Meteosat Third Generation (MTG) mission. The first optical filter is a Solar Rejection Window (SRW) to limit the solar thermal radiation absorbed by the optical head while the second optical filter is a Narrow Band Filter (NBF) intended to only pass the lightning discharge emission wavelengths. Each filter has its own distinctive design considerations and manufacturing challenges. The SRW must pass wavelengths from the 760 to 780 nm spectral range and reject (block) wavelengths from the ultraviolet (UV) to the mid-wave infrared (MWIR) and up to 16.3° angle of incidence (AOI) and over a large temperature range (as when exposed to direct sunlight). The NBF is designed to pass only the oxygen emission triplet, centered around the 777.6 nm (vacuum) wavelength and rejecting other wavelengths. Considering the AOI of the light and the temperature excursion, the center wavelength (CWL) uniformity has to be better than 0.04% peak-to-valley (PV) over the 114 mm diameter clear aperture, which is a formidable challenge. We achieved a coating thickness uniformity less than ±0.01% PV, exceeding the prescribed specification. Post-deposition annealing was carried out to tune the bandpass to within pico-meters (pm) of the target CWL value while maintaining the desired CWL uniformity. To ensure that both the SRW and NBF filter meet the desired optical and physical specifications, a comprehensive series of optical and physical characterization tests, along with durability tests, were carried out on each deposition batch.
An automated system for hydroxide catalysis bonding of precision-aligned optical systems
Author(s):
D. I. Robertson;
W. Brzozowski;
E. D. Fitzsimons;
C. J. Killow;
P. Parr-Burman;
M. Perreur-Lloyd;
D. Pearson;
H. Ward;
M. Wells
Show Abstract
Precision-aligned, robust, ultra-stable optical assemblies are required in an increasing number of space-based applications such as fundamental science, metrology and geodesy. Hydroxide catalysis bonding is a proven, glue-free, technology for building such optical systems from materials such as ULE, Zerodur and fused silica. Hydroxide catalysis bonded optical systems have flown in missions such as GP-B and LISA Pathfinder achieving picometer path-length stability and microradian component stability over full mission lifetime. Component alignment and bonding was previously a largely manual process that required skilled operators and significant time. We have recently automated most of the alignment and bonding steps with the goals of improving overall precision, speed and reliability. Positioning and bonding of an optical component to within 4 microns and 10 microradians of a target position and alignment can now be reliably completed within half an hour, compared to the many hours typically taken previously. The key new features of this system are an interferometer that monitors the parallelism and separation of the surfaces to be bonded and a precision multi-axis manipulator that can optimise component alignment as it brings it down to the point of bonding. We present a description of the system and a summary of the alignment results obtained in a series of 9 test bonds. We also show how this system is being developed for integration into a precision optical manufacturing facility for assembly of large optical systems
Convex blazed gratings for high throughput spectrographs in space missions
Author(s):
Frédéric Zamkotsian;
Igor Zhurminsky;
Patrick Lanzoni;
Nicolas Tchoubaklian;
Christian Schneider;
Sören Fricke;
Marc Schnieper;
Fabian Lütolf;
Clément Luitot;
Vincent Costes
Show Abstract
In next generation space instrumentation for Earth and Universe Observation, new instrument concepts include often non planar gratings. Their realization is complex and costly. We propose a new technology for designing and realizing convex blazed gratings for high throughput spectrographs.
For this purpose, our requirements are driven by a Digital-Micromirror-Device-based (DMD) MOS instrument to be mounted on the Telescopio Nazionale Galileo (TNG) and called BATMAN. The two-arm instrument is providing in parallel imaging and spectroscopic capabilities. The objects/field selector is a 2048 x 1080 micromirrors DMD, placed at the focal plane of the telescope; it is used as a programmable multi-slit mask at the entrance of the spectrograph. The compact Offner-type spectrograph design contains a low density convex grating to disperse light. For optimization of the spectrograph efficiency, this convex grating must be blazed.
A blazed reflective grating has been designed with a period of 3300 nm and a blaze angle of 5.04°, and fabricated into convex substrates with 225 mm radius of curvature and a footprint diameter of 63.5 mm. The blaze is optimized for the center wavelength of 580 nm within the spectral range of 400 – 800 nm. Convex blazed gratings have been fabricated and coated with protected silver, with a final 5.7° blaze angle over the whole surface. Efficiency close to 90% on the 1st diffraction order at 700nm has been obtained.
This new type of non-planar reflective gratings will be the key component for future high throughput spectrographs in space missions.
Highly stable Zerodur based optical benches for microgravity applications and other adverse environments
Author(s):
J. P. Marburger;
Moritz Mihm;
Ortwin Hellmig;
André Wenzlawski;
Patrick Windpassinger
Show Abstract
A number of cold atom experiments are restrained by the impeding effects of gravity. While efforts have been made to overcome these limitations in a gravitational environment, another approach is placing the experiment in a microgravity environment, as can be found aboard sounding rockets, satellites or a space station.
The cornerstone of such experiments is a robust laser system. The adverse conditions during a rocket launch impose stringent requirements on thermal stability and resilience against mechanical stress on this part of the experimental setup. Furthermore, the very limited space found on any of the aforementioned microgravity platforms necessitates maximal miniaturization.
In order to meet these requirements, we have developed a technology based on miniaturized free-space optics, mounted onto optical benches made from Zerodur, a glass-ceramic which exhibits a vanishing first order coefficient of thermal expansion. The technology has already been successfully implemented in the sounding rocket missions FOKUS, KALEXUS and MAIUS−1. It will also be used in the upcoming MAIUS−2/3 sounding rocket missions. To meet the even more restrictive size and mass constraints of the NASA-DLR Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL) mission, a quantum optics multi-user facility aboard the International Space Station, we are currently investigating a new and improved design concept. While being motivated by these missions, our technology can be expanded to any other experimental field where a small and robust laser system is needed.
Optical beam steering on distribution boards and its application for atom quantum experiments in space
Author(s):
I. Drougkakis;
K. G. Mavrakis;
K. Poulios;
G. Vasilakis;
D. G. Papazoglou;
W. von Klitzing
Show Abstract
We present a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling schemes on optical breadboards, which uses glass wedge pairs and plates to correct for angular and translational misalignments respectively. This technique finds application in proposed missions for atom quantum experiments in space, e.g. where laser beams are used to cool and manipulate atomic clouds. The key advantage compared to the conventional beam steering is that OBST permits extremely fine adjustments whilst being far less sensitive to alignment errors and mechanical drifts. Beam steering resolutions of better than 5 μrad and 2 μm are achieved, resulting in a resolution in coupling efficiency (CE) of 0.1%. The inclusion of OBST on an optical breadboard reduces the requirements on the pointing and position precision adjustment of the fiber couplers, leading to a much-simplified design. The simpler construction of the couplers combined with the reduced sensitivity to drifts increases the stability-reliability of the breadboard and reduces the production duration and cost. We demonstrate CE of up to 90%, with a stability of 0.2% in a stable temperature environment and 2% over a temperature range from 10-40 degrees Celsius. We do not observe any change in the performance after large temperature changes.
Temperature control of a PM ring fiber cavity for long-term laser frequency stabilization
Author(s):
D. -H. Phung;
J. -P. Coulon;
M. Lintz;
T. Lévèque
Show Abstract
We present a high performance, low cost, simple setup for long term temperature stabilization of a 2 m optical fiber ring cavity for laser frequency stabilization applications thanks to birefringence of the fiber and its dependence on temperature. The fiber temperature is controlled, at millisecond time scale by LED (light emissive diode) illumination. This allows reaching a temperature stability of 0.1 μK at 100 seconds for the 2 m long PM ring fiber cavity. This is a reduction of the fiber temperature by a factor of 2×105 (from 20 mK to 0.1 μK) and 5×105 (from 300 mK to 0.6 μK), at 100 seconds and at 105 seconds, respectively, with respect to the ambient temperature variations.
Interferometric multi-core fiber optic gyroscope under temperature changing environment
Author(s):
Shinji Mitani;
Kenichiro Nigo;
Satoshi Karasawa;
Haruyuki Endo;
Taketoshi Takahata
Show Abstract
We have proposed an interferometric fiber optic gyro (I-FOG) with a novel sensing fiber coil consisting of multi-core fiber (MCF) spliced with fan-in/fan-out (FIFO) devices. This sensing coil can improve the sensitivity of I-FOG without escalating the hardship of winding process of fiber to form coils. We have fabricated a seven-core MCF coil with FIFO devices and demonstrated the proper operation of the proposed I-FOG for the first time. The angular random walk performance of 0.002 deg/√h was achieved, thereby confirming that the seven-core waveguide loop works successfully as a Sagnac interferometer as expected. In addition, we evaluated the effect of temperature changes ofMCF and FIFO devices that cause fluctuations in the measured rotation rate. We confirmed that this effect shows essentially the same features as Shupe effect (non-reciprocal phase shift error due to changing environmental temperature) which is a well-known feature of conventional I-FOGs.
Semiconductor laser modules for precision spectroscopy applications in space
Author(s):
A. Bawamia;
Ch. Kuerbis;
R. Smol;
A. Wicht
Show Abstract
The Ferdinand-Braun-Institute has been developing high-power, narrow-linewidth semiconductor lasers for precision spectroscopy applications in harsh environments for more than ten years. Starting with hybrid-integrated diode laser chips and micro-optics on a ceramic platform for Bose-Einstein condensation experiments in a drop tower, the institute is now developing, qualifying and, in many cases, already delivering fully-packaged, multi-functional modules for application on platforms including sounding rockets, the International Space Station (ISS) and nano-satellites. We present the latest generation of electro-optical modules, which is designed to accommodate any two semiconductor chips. This includes, amongst others, the ECDL-MOPA, where the laser architecture consists of an ECDL and a semiconductor optical amplifier, both hybrid-integrated into a sealed package within a footprint of a conventional smartphone (but with a height of approx. 23 mm). The single-mode, polarization-maintaining optical fiber output delivers, for instance, 570 mW of power and a free-running FWHM linewidth of approximately 30 kHz (within a timescale of 1 ms) at the operating wavelength of 1064.49 nm. One such module has already been successfully launched on a sounding rocket mission in May 2018.
2-μm pulsed Holmium laser for a future CO2/ H2O space lidar mission
Author(s):
Fabien Gibert;
Dimitri Edouart;
Claire Cénac;
Paul Monnier
Show Abstract
In the context of greenhouse gases monitoring such as carbon dioxide (CO2), a powerful emitter in the near infrared (1.5−2 μm) is needed to get a useful precision on concentration measurement (< 1 %) with reasonably space and time resolution. Energy pulses larger than several millijoules at a pulse repetition frequency (PRF) of several hundred of Hertz are usually required. Such requirements call for a solid-state laser configuration at least for a part of it as demanded pulse energy is well beyond current pulsed fiber laser potential performances. These DIAL emitters also call for a specific multiple wavelength emission around the chosen atmospheric gas absorption line, single mode operation, high spectral purity and stability, high pulse energy stability, good beam quality, linear pulse polarization and good overall wall plug efficiency, especially for space Integrated Path Differential Absorption (IPDA) lidar measurements. In this paper we report on the development and the demonstration of a two-wavelength single-frequency Ho:YLF oscillator that was developed in the framework of a ESA contract. This laser is especially suitable for atmospheric carbon dioxide (CO2) measurement using the R30 CO2 absorption line at 2050.967 nm. The oscillator consists in a fiber-coupled and freespace solid-state hybrid system and can be used in high-energy middle-rate or moderate-energy high-rate configurations depending the detection scheme of the lidar. The pulse energy and frequency stabilities are specially documented in twofrequency single-mode operations in the context of CO2 space borne IPDA measurements.
Analysis of pulse position modulated fiber-based laser systems for deep space optical communication
Author(s):
Pawel Grzes;
Maria Michalska;
Jacek Swiderski
Show Abstract
Fiber-based laser sources delivering optical pulses at a wavelength of ~1.5μm have attracted a great interest in recent years mainly due to their unique properties. High efficiency, high output power, eye-safe wavelength and very good output beam quality make them a perfect tool for Free Space Optics communication. The most suitable modulation scheme for long-haul communication is pulse-position modulation mainly due to its high peak-to-average power ratio. In this paper we discuss a potential use of high power fiber laser system built in Master Oscillator Power Amplifier architecture for pulse-position modulated Deep Space Optical Communication. We focus on power scalability, beam quality, laser driver simplicity and temporal deformation of nanosecond laser pulses as well. In summary we shortly compare features of pulse-position modulated fiber laser transmitter with other high power laser sources being used in optical communication.
FULAS: high energy laser source for future LIDAR applications
Author(s):
Sven Hahn;
Markus Bode;
Jörg Luttmann;
Dieter Hoffmann
Show Abstract
Reliable high energy laser sources had been proven in the past to be the bottle neck for space-borne LIDAR instruments. The presented FULAS laser optical design concept and the developed technologies define a technology baseline for a high variety of potential LIDAR applications. The technology provides a reliable space compatible system design, optimized with respect to lifetime and in especial laser induced contamination. The applied design principles and modularity allow proven energy scalability, flexible modes of operation and a manifold of opportunities for tailoring of the output wavelength. The concept, some details of the design and the potential for future application are addressed in this publication
Space validation of 1550nm DFB laser diode module
Author(s):
Philip Henderson;
Adrian Norman;
John MacDougall;
Paul Naylor;
Efstratios Kehayas;
Lip Sun How;
Sébastien Lhuillier;
Alain Bensoussan;
Mustapha Zahir
Show Abstract
Following a program funded by the European Space Agency, a novel laser-diode module has been created and tested to ESCC-23201-compliant space standards. Manufactured by Gooch & Housego, the module is set for imminent entry to the European space market for use in optical signal-processing and telecom systems. Emission is from a 1550nm DFB semiconductor laser diode driven at constant nominal current and temperature. Combined with a wavelength stability of better than ±0.1nm and internal data rate of up to 3.2GHz, innovative sub-design and packaging provides for a unique power capability comprising a start-of-life ex-fibre power of >90mW and a typical electric power consumption that, at <4.1W, is down to 25% of that of similar products. Validation testing by AdvEOTec (France) indicates a comprehensive set of space compliances such as in proton irradiation, humidity, hot/cold storage, rapid depressurisation, vibration and 1,000g shock, as well as immunity to ±8kV of ESD, 10-5mbar of vacuum, and 100krad of gamma irradiation. Unique methodologies for life-test modelling and production screening, established by Thales Alenia Space (France), provisionally confirm a 15-year space-compliant operating life. Space-compliant product, as presented, is intended to be supplied for a period of at least 5 years.
Optical design and characterization of the MOMA laser head flight model for the ExoMars 2020 mission
Author(s):
A. Büttner;
M. Ernst;
M. Hunnekuhl;
R. Kalms;
L. Willemsen;
P. Weßels;
D. Kracht;
J. Neumann
Show Abstract
A space-qualified flight model of a pulsed ultraviolet (UV) laser has been developed for the Mars Organic Molecule Analyzer (MOMA) instrument of the ExoMars 2020 mission. The design is based on a passively Q-switched Nd:Cr:YAG laser oscillator with subsequent two-stage frequency quadrupling. It emits nanosecond pulses with an energy tuneable between 13 μJ and 130 μJ at a wavelength of 266 nm.
Considering its small physical dimensions and weight, the interior of the laser head is rather complex. Besides the aforementioned infrared oscillator and frequency conversion stage it contains the pump optics, two wavelength division assemblies within main beam path, a complex monitoring stage including two photodiodes for pulse energy measurement, a beam shaping setup and a deflection unit for fine adjustment of the beam pointing towards the sample location within the instrument. Most of the laser head is enclosed in a hermetically sealed housing, while the deflection unit is sealed separately. Both volumes are filled with 1 bar of dry, filtered air.
A miniaturized high energy laser for ignition of rocket engines
Author(s):
G. Kroupa;
M. Börner
Show Abstract
During the last years the CTR HiPoLas ignition system, originally developed for the ignition of automotive engines, has reached a sufficiently high level of stability and miniaturization to enable competitive operation on space craft engines 1. The fifth generation of this Nd:YAG laser system has been customized especially for the ignition of cryogenic thrust chambers and has been tested on a variety of combustors reaching more than 1500 successful engine ignitions. The high reliability and compactness of the system lies within the monolithic, side-pumped resonator concept requiring no adjustments of any optical element during assembly and thus rendering the laser unsusceptible against vibrations and thermal influences. The standard version of the system is able to generate up to 35mJ at 2ns with repetition rates up to 100 Hz in burst mode, a new high energy version uses an additional amplifier stage to boost the energy output up to 70mJ. Applications of the laser ignition system include high trust engines as well as combustion chambers at thrust levels of orbital maneuvering and reaction control systems. Technology readiness tests verified the applicability, stability and reliability of the laser ignition system for a variety of injector configurations, furthermore, ignition based on laser ablation was investigated. The laser igniter system was used to re-ignite a high thrust combustor up to 60 times in a row and in total more than 1500 times within one test campaign without laser system failure2.
Mechanical design and testing of the MOMA flight model laser head for the EXOMARS 2020 mission
Author(s):
M. Ernst;
A. Büttner;
M. Hunnekuhl;
R. Kalms;
L. Willemsen;
P. Wessels;
D. Kracht;
J. Neumann
Show Abstract
A hermetically sealed laser head (LH) emitting laser pulses at a wavelength of 266 nm has been developed and tested for the Mars Organic Molecule Analyzer (MOMA) instrument of the ESA/Roscosmos ExoMars 2020 mission. MOMA comprises a gas chromatograph (GC) and a laser desorption mass spectrometer (LDMS). Its primary function is to search for traces of present or past signs of organic molecules in subsurface material probes. The LH is used as an excitation source for the LDMS part of MOMA. Its design fulfils stringent mass and volume requirements and is realized as a hermetically sealed system. It consists of a laser diode pumped Nd:YAG based laser oscillator, a frequency conversion stage for frequency quadrupling of the fundamental laser oscillator wavelength, a compact monitoring stage for internal laser pulse detection, a beam shaping telescope and an adjustable laser beam steering unit with the purpose of guiding the generated UV laser beam to its target position in front of the mass spectrometer (MS) ion inlet.
The system has undergone extensive functional and environmental testing including vibration, shock and thermal vacuum chamber tests. After completion of the functional and environmental test campaign, the LH has been integrated on the MOMA mass spectrometer. Here we report on the mechanical design of this LH and its environmental testing. Furthermore, the LH was successfully tested both functionally and environmentally on LDMS level.
Optical gain beyond Hakki-Paoli. a new power tool for reliability of laser diodes
Author(s):
M. Vanzi;
G. Mura;
V. Sanna Valle
Show Abstract
Simpler procedures for gain measurements in commercial laser diodes are introduced. They fully agree with the results of the popular Hakki-Paoli method, greatly extend its application range and remove those practical constraints that reserve practical gain measurement to the sole device designer and manufacturer. The aim of the paper is to propose the new method for reliability studies, to support and address the investigation of Failure Physics of semiconductor lasers. Some recent puzzling case histories are also summarized, that did not benefit of the new method. Their role is to point out how many unsuspected, and even unexplained physical phenomena may affect a technology that is not yet really assessed.
Forward error correcting code for high data rate LEO satellite optical downlinks
Author(s):
S. Poulenard;
B. Gadat;
J. F. Chouteau;
T. Anfray;
C. Poulliat;
C. Jego;
O. Hartmann;
G. Artaud;
H. Meric
Show Abstract
A simulation framework based on a physical-layer based abstraction to predict physical layer performances and to compare different forward error correcting (FEC) codes is presented. This framework is used to jointly design interleaving and FEC schemes for free space optical link. A sub-class of regular Low-Density Parity-Check codes is shown to be an interesting alternative to current space communication standard for optical links that require low error floor and high decoder throughput. End-to-end simulations show the feasibility of error free link from a LEO satellite to a high complexity ground station at 25Gbits/s and from a LEO satellite to low complexity optical ground station at 10 Gbits/s. The proposed protection scheme is composed of FG LDPC code and a bit interleaver to span the burst of errors.
Optical feeder link architectures for very HTS: ground segment
Author(s):
Nicolas Girault;
Pantelis-Daniel Arapoglou
Show Abstract
The paper deals with an analysis of Very High Throughput Satellite (VHTS) systems employing optical feeder links. As the capacities of newly announced next generation VHTS systems are exceeding the Terabit/s barrier, a large amount of investment needs to be directed not only to the space segment (as was the case traditionally), but also to the ground segment in support of the feeder links. To reduce this investment, satellite operators are reviewing various options and technologies for the feeder links, among which optical feeder links [1]. In this paper, different approaches are analysed for ground segment networks relying on Optical Ground Stations (OGS), exploring the concept of smart gateway diversity with N active OGS and P redundant ones, like is currently done in VHTS systems with RF feeder links. OGS locations are assessed in terms of aggregate availability and total cost for the satellite operator, which is an essential element for the viability of the VHTS system. Different options are assessed for the distribution of OGS gateway processing functions (local at OGS or centralised), and for their interconnection. The main technical challenges are discussed, identifying which technologies will be required for an operational VHTS system with OGS.
Numerical prediction and experimental validation of irradiance fluctuations in a pre-compensated optical feeder link
Author(s):
K. Kudielka;
E. Fischer;
T. Dreischer
Show Abstract
This paper focuses on optical links from ground to a geostationary satellite, using adaptive optics to pre-compensate the wave-front of the uplink beam. We present the numerical prediction of the irradiance statistics at the satellite. Uplink beam diameters, as well as the turbulence strength in the boundary layer and in the tropopause are varied. Results show, that the choice of uplink beam diameter significantly affects the fading statistics, in particular the shape of the probability density function. In a realistic worst case (30° elevation, day-time turbulence, sea level), the optimum beam diameter, showing minimum irradiance fluctuation at the target, is around 20 cm. In that case, the probability of fades larger than 6 dB (with respect to the diffraction limit) is approx. 10
-3.
A breadboard of such a closed-loop adaptive-optics pre-compensation system has been implemented. It comprises a Shack- Hartmann wavefront sensor, two tip/tilt mirrors, a 140-element deformable mirror, a far-field propagation simulator, and two rotating turbulence phase screens (simulating tropopause and atmospheric boundary layer, respectively). The link geometry is representative of the intended application in an optical feeder link for geo-stationary satellites. Preliminary test results confirm the numerical predictions.
Nonlinear Array detection strategies for optical beams in long range fee-space optics channels
Author(s):
Kamran Kiasaleh
Show Abstract
In this study, we examine the problem of array detectors for free-space optical (FSO) communication systems when the optical field is detected using an array of detectors in the presence of large background noise and non-negligible pointing error. It is assumed that the spatial pointing errors are due to beam tilt and/or platform vibration. We propose and study a nonlinear detection mechanism for processing the outputs of the photodetectors (PD). The proposed strategy performs photodetector array combining that favors the PDs with non-negligible signal strengths, which are proportional to the spatial characteristics of the beam. Provided that the spatial profiles of the optical beams in single and multiple-spatial-mode scenarios are non-uniform, uniform aperture detector arrays will provide only a suboptimal performance. That is, the spatial feature of the detector is assumed to match the spatial feature of the received beam. This principle mirrors the concept of matched filtering in time domain for the detection of signals buried in additive white Gaussian noise. Performance in this paper is established in terms of the overall bit error rate for direct-detection receivers. It is shown that the proposed detection strategy results in a sizeable gain in performance in terms of reducing the bit error rate by an order of magnitude for all conditions, including when the pointing error is substantial.
Experimental evaluation of adaptive distributed frame repetition at 10Gbps for the satellite-to-ground optical link
Author(s):
Toshiharu Ito;
Yoshimasa Ono;
Yohei Hasegawa;
Manabu Arikawa
Show Abstract
Performance instabilities due to the fading are vital subjects for long distance free space optical communication systems in which the signal lights travel through the atmosphere. The straightforward approach is to introduce the combinations of optical transmitters and receivers that can operate in various modulation speeds, and the operator selects the speed from the candidates in order to manipulate photons per bit according to the link conditions. However, the realization of such functions with single hardware may result in the halfway capabilities. For these problems, our group has been proposing the use of the technologies that we call Adaptive Distributed Frame Repetition (ADFR), in which a high-speed link is divided in time, and sending node replicates frames and transmits over a single link with the proper time intervals without concerning whether each frame arrives at the destination or not. Since the line rate is always constant, and functions equipped in the receiving node are simple, settings at the transmitting node relating to retransmission can be switched seamlessly without any negotiations with the opposite. In this time, the main functions of ADFR are implemented on the computers to be experimentally evaluated at 10 Gbps. In addition to the basic results about static and dynamic performances of ADFR, the combined performance with TCP assumed to be introduced in the GEO-Ground system will be discussed in the paper.
Research and Development of a Transportable Ground Optical Station in NICT
Author(s):
Yoshihiko Saito;
Yasushi Munemasa;
Hideki Takenaka;
Hiroo Kunimori;
Dimitar Kolev;
Alberto Carrasco-Casado;
Yoshisada Koyama;
Koichi Shiratama;
Toshihiro Kubo-oka;
Morio Toyoshima
Show Abstract
In recent years, the necessity of satellite-to-ground optical communication has increased as a method for realizing higher-speed communications between satellites and the ground. However, one disadvantage of free-space optical (FSO) communication is the significant influence of the atmosphere. FSO communications cannot be utilized under certain atmospheric conditions, such as cloudy skies. One of the solutions to this problem is site diversity, which makes it possible to select a given ground station with better atmospheric conditions among a number of fixed ground stations. The other solution is to prepare a ground station that can be moved to a place with better atmospheric conditions. In this paper, we present the development of a transportable optical ground station currently being researched in NICT.
In order to be transportable, it is necessary to build a system capable of travelling on public roads, installable in every place, and ready to be loaded on relatively-light trucks. For this purpose, a realistic telescope diameter is about 30 cm at the maximum, capable of being set up quickly, and with a pointing accuracy of about 100 μrad. In addition, it is necessary to prepare a fine-pointing optical system that performs tracking with about 1/10 of the pointing accuracy of the telescope. In this research, we will develop the base of the transportable optical ground station using the knowledge of mobile astronomical telescopes. With respect to tracking, we will develop a smaller and lighter fine-tracking system based on NICT’s previous experience. If necessary, we plan to develop an adaptive-optics system for correcting atmospheric disturbances to improve the fiber-coupling efficiency of the communication laser beam.
Assessment of the effective performance of DPSK vs. OOK in satellite-based optical communications
Author(s):
A. Maho;
M. Faugeron;
A. Le Kernec;
K. Elayoubi;
M. Sotom
Show Abstract
This paper reports on the assessment of the communication performance of DPSK- and OOK-based free-space optical (FSO) links in satellite-based applications, including LEO downlinks, LEO inter-satellite links, and feeder links for GEO Satellites. The performance is assessed by means of simulations as well as transmission experiments at 10 Gbps. The impact of optical filter bandwidth, optical delay-line-interferometer accuracy, frequency offset between transmitter laser and receiver, is quantified. OOK performance critically depends on transmitter extinction ratio, and proves robust to Doppler-induced frequency offsets. DPSK is sensitive to any laser wavelength drift and offset with the DLI response. Nevertheless, compensation of this drift is considered manageable, making it possible to maintain the 3dB advantage of DPSK vs. OOK in practical use conditions.
Assessment of gamma and proton radiation effects on 100 Gbps commercial coherent optical transceiver
Author(s):
Raichelle Aniceto;
Slaven Moro;
Andrew Grier;
Randall Milanowski;
Kerri Cahoy
Show Abstract
The Acacia AC100M is a 100 Gigabits per second (Gbps) commercial, coherent optical transceiver module with digital signal processing (DSP) application specific integrated circuit (ASIC). The AC100M was characterized with noise-loaded input to simulate power-starved link operation on the receiver and decoder for performance testing. Gamma radiation and 65 MeV proton radiation test campaigns at Defense MicroElectronics Activity (DMEA) and UC Davis Crocker Nuclear Laboratory (CNL), respectively, were completed to assess single event effects (SEEs) and total ionizing dose (TID) effects on the AC100M. After exposure to gamma radiation with TID level of ~13.7 krad(Si), communication with the AC100M module was lost and power cycling of the module and evaluation board could not restore nominal operation. The AC100M ASIC survived and experienced no performance degradation from proton equivalent TID exposure up to 66.7 krad(Si) with proton radiation. After proton equivalent TID level of 101 krad(Si), the AC100M did not functional nominally after power cycling. The calculated AC100M ASIC proton SEE cross section was 4.39×10-10 cm2 at the 65 MeV proton energy level.
Range dependence of pulse position modulation in the presence of background noise
Author(s):
Marcin Jarzyna;
Wojciech Zwolinski;
Konrad Banaszek
Show Abstract
We identify the maximum attainable transmission rate of a noisy optical link employing the pulse position modulation (PPM) format with direct detection. We show that for a fixed background noise level it is possible to achieve the information rate directly proportional to the average detected signal power in the photon-starved regime. This implies inverse-square scaling with the distance, presenting a qualitative improvement over previously obtained estimates that scaled as the inverse of the fourth power of the distance. The necessary ingredients to achieve the improved mode of operation are the unrestricted optimization of the PPM order and the complete decoding of detection events to extract information from sequences containing multiple counts within one PPM frame. Importantly, information efficiency equivalent to high-order PPM formats can be attained using signals with uniformly distributed optical power processed with recently proposed structured optical receivers.
Feasibility study of a scalable laser communication terminal in NICT for next-generation space networks
Author(s):
Yasushi Munemasa;
Yoshihiko Saito;
Alberto Carrasco-Casado;
Phuc V. Trinh;
Hideki Takenaka;
Toshihiro Kubo-oka;
Koichi Shiratama;
Morio Toyoshima
Show Abstract
Recently, satellite broadband communication services using Ka-band are emerging all over the world, some requiring capacities in excess of 100 Gbps. With the radio bandwidth resources becoming exhausted, high-speed optical communications can be used instead to achieve ultra-broadband communications. The National Institute of Information and Communications Technology (NICT) in Japan has over 20 years of experience in R&D of space laser communications with missions such as the Engineering Test Satellite VI (ETS-VI), OICETS, and SOCRATES/SOTA. We are currently developing a laser communication terminal named “HICALI”, aiming to achieve 10 Gbps-class space communications with a 1.5 μm-band laser beam between optical ground stations (OGSs) and the next generation high throughout satellite called ETS-IX with a hybrid communication system using radio and optical frequencies, which will be launched into the geostationary orbit in 2021. Moreover, we have studied laser communication terminals for terrestrial networks, as an alternative wireless system to radio frequency (RF) band. In 2014, we developed a terrestrial free-space optical communications network facility, named INNOVA (IN-orbit and Networked Optical ground stations experimental Verification Advanced testbed). Many demonstrations have been conducted to verify the feasibility of sophisticated optical communications equipment in orbit.
We have conducted a feasibility study of a laser communication terminal for next-generation space networks following the above R&D trends in space communication networks, which is a high-speed, secure, small, and scalable laser communication terminal for optical ground stations (OGSs) and satellites or airborne terminals. In this paper, we describe the plan of NICT to develop a scalable laser communication terminal for next-generation space networks.
Utilizing time-bandwidth space for efficient deep-space communication
Author(s):
Konrad Banaszek;
Michal Jachura;
Wojciech Wasilewski
Show Abstract
We discuss modulation formats that warrant high information efficiency of deep-space optical links under given power constraints. The discussion is framed using the theoretical concept of orthogonal optical modes occupying the available time-bandwidth space. With diminishing average signal power, the challenge is to concentrate the entire optical energy in very few of these modes. In the generic case of pulse position modulation (PPM), where optical modes occupy separate time bins, this results in increasing peak-to-average power ratio requirements for the transmitter light source. Equivalent information efficiency can be attained using frequency shift keying (FSK) employing modes that do not overlap in the spectral degree of freedom and have uniformly distributed instantaneous optical power in the temporal domain. Recently, efficient modulation formats have been proposed that use words composed from the binary phase shift keying (BPSK) alphabet. Such words can be converted after transmission into the PPM format with the help of structured optical receivers. Selected technical aspects of physical implementations of links based on different modulation formats are briefly reviewed.
An adaptive coded transmission scheme utilizing frozen bits of polar code in satellite laser communications
Author(s):
K. Ito;
E. Okamoto;
H. Kunimori;
M. Toyoshima
Show Abstract
Free-space optical communication for a satellite-to-ground link using wideband 10-THz lasers can realize a higher capacity than radio frequency (RF) communications, and use downsized and energy-efficient components. Thus, satellite laser communication is expected to be used in new communication infrastructures. However, in wireless optical communication, problems such as disturbances due to atmospheric fluctuation and tracking/capturing errors of the laser beam occur, leading to a reduction in the received optical power. Thus, powerful channel coding is essential. On the other hand, it is strictly proven that polar code asymptotically reaches the channel capacity with sufficiently long code length. To obtain the excellent decoding characteristics of the polar code, it is necessary to adequately set frozen bits that are shared by the transmitter and the receiver, and an arbitrary code rate can easily be achieved by controlling the number of frozen bits. However, when considering the application of adaptive polar code to satellite laser communications, there are some difficulties in the transmission link such as large delays or received power fluctuation caused by air turbulence. Thus, it is difficult to realize an adaptive coding scheme for the channel with two-way information control. Therefore, in this paper, we propose a one-way adaptive polar coding scheme that estimates the transmission rate without requiring control information by superimposing code rate information into frozen bits, and estimating the code rate by decoding them at the receiver side. We evaluate the characteristics of this method using computer simulations.
Assembly and integration of optical downlink terminal VSOTA on microsatellite RISESAT
Author(s):
Hannah Tomio;
Toshinori Kuwahara;
Shinya Fujita;
Yuji Sato;
Morokot Sakal;
Hiroo Kunimori;
Toshihiro Kubooka;
Hideki Takenaka;
Yoshihiko Saito;
Morio Toyoshima
Show Abstract
The Rapid International Scientific Experiment Satellite (RISESAT) is a 50-kg-class Earth observation microsatellite that is currently being developed at the Space Robotics Laboratory (SRL) of Tohoku University, with a planned launch data in 2018. Intended to demonstrate a cost-effective and reliable microsatellite bus system, RISESAT features various scientific payload instruments from institutions and organizations around the world. Among the payloads are the Very Small Optical Transponder (VSOTA), a compact, dual-band (980 nm, 1550 nm), lightweight laser signal transmitter developed by the Japanese National Institute for Information and Communications Technology (NICT), and the High Precision Telescope (HPT), a multi-spectral, high-resolution Cassegrain telescope developed by Hokkaido University and intended for Earth and astronomical observations. Using these two payloads, RISESAT can demonstrate satellite-toground one-way laser communication. This experiment is intended to demonstrate optical communication capability within the scope of the available hardware resources on a microsatellite dedicated to numerous other scientific endeavors. Hence, VSOTA is lighter, less power intensive, and more simplified than other optical transmitter terminals. Internal gimbal mechanisms for fine pointing have also been eliminated, thus the tracking of the optical ground stations will be achieved using body pointing of the satellite. Recently, end-to-end electrical configuration and communication tests have been conducted for both the engineering model (EM) and the flight model (FM) of the VSOTA assembly. This paper provides an overview of VSOTA and its space-to-ground optical communication demonstration, and describes the current status of the RISESAT optical communication subsystem assembly and integration.
Development of “HICALI”: high speed optical feeder link system between GEO and ground
Author(s):
T. Kubo-oka;
H. Kunimori;
K. Suzuki;
Y. Koyama;
K. Shiratama;
Y. Munemasa;
H. Takenaka;
D. Kolev;
A. Carrasco Casado;
T. Phuc;
M. Toyoshima
Show Abstract
In National Institute of Information and Communications Technology (NICT) of JAPAN, an ultra high speed optical satellite communication equipment onboard the engineering test satellite IX has been developing. The satellite is planned to be launched to geosynchronous orbit in 2021. In this project, we are aiming for ultra high-speed data transmission at the world's highest level of 10 [Gbps] for both uplink and downlink between optical ground stations and geosynchronous satellite. This paper outlines the optical communication mission, the scheduled optical communication experiment, the examination of HICALI and the ground based system at the present time - the outline of the development situation is also explained.
Performance validation of a high-bandwidth fine steering mirror for optical communications
Author(s):
G. Witvoet;
S. Kuiper;
A. Meskers
Show Abstract
This paper presents the first test results of a novel Fine Steering Mirror (FSM) for optical communication terminals. The FSM utilizes efficient variable reluctance actuators, tailored for the specific application, making it highly compact and power efficient. The test results demonstrate a high dynamical performance of <1.7kHz closed-loop bandwidth, and an optical angular range of more than ±2° in two axes. The actual optical angular jitter is less than 1.5 μrad. These numbers demonstrate that this FSM is highly suitable for the evolving field of inter-satellite laser communications.
Tracking challenges of QKD over relay satellite
Author(s):
S. Sharma;
N. Perlot;
J. Rödiger;
R. Freund
Show Abstract
We investigate a quantum key distribution (QKD) system with relay satellite for communication between two distant Earth-based parties, Alice and Bob. The satellite acts as a relay station which simply redirects the QKD signal. It has several advantages that can be decisive. The optical relay provides a high transparency to protocols and wavelengths. The relay node does not have to be trusted. Like entanglement-based or measurement-device-independent satellite QKD, relayassisted QKD suffers from a higher propagation loss than trusted-node scenarios. Challenges are expected when pointing the relay mirror precisely between Alice and Bob and dealing with significant point-ahead angles that result from the satellite velocity. We start our analysis by evaluating the point ahead angles (PAA) of Alice and Bob for scenarios of interest. The difference between the two PAA vectors tells us whether the relay mirror will be able to maintain a bidirectional transmission with beams sent from the ground. Considering a satellite altitude of 500 km and an Alice-Bob separation of 1000 km, observation of large PAA vector difference enjoins us to place additional beacon sources on the satellite. A conceptual design of the relay-tracking system is drafted. Onboard measurements of the beacons from Alice and Bob provide feedback to the relay-mirror positioning control loop. With a typical relay-mirror size of 0.2 m, propagation losses are calculated for different ground antennas. We conclude on the attractiveness and feasibility of satellite relay QKD.
Integration ghosts in interferograms: origin and correction
Author(s):
D. Lamarre;
C. Keim;
T. Guggenmoser
Show Abstract
We report on an error source and a possible correction which occurs with Fourier Transform Spectrometers due to the use of an integrating detector.
The new class of imaging Fourier-Transform-Spectrometers (FTS) is in many cases best realised using continuously moving mirrors and an integrating array detector with fixed frame rate. In case of not perfectly constant optical path difference (OPD) speed, this corresponds to an irregular OPD sampling, resulting in radiometric errors. This effect is well-known and can be solved by resampling, i.e. interpolation on a regular OPD grid.
A less known effect is caused by the detector integrating over constant time intervals, which – like the sampling steps - are also of varying length in the OPD domain due to the non-constant OPD speed. The resulting error is discussed in the presented paper, where also an elegant correction method is proposed.
Constant-width integration in the OPD domain acts as a spatial low-pass filter on the interferogram. If the integration width varies, a modulation is applied to the interferogram’s envelope. This modulation results in a radiometric error in the spectrum.
The presented correction is a finite impulse response filter with only three taps, to be applied to the measured time-sampled interferogram before resampling. In case the interpolation is done with filters, these filters and the new 3-tap filter can be combined to reduce processing overhead.
Acousto-optic interaction model with mercury halides (Hg2Cl2 and Hg2Br2) as AOTF cristals
Author(s):
A. Pierson;
C. Philippe
Show Abstract
Acousto-optic tunable filters (AOTF) are used in the development of hyperspectral imagers from the ultra violet (UV) to the long wave infrared (LWIR). They have the advantage to be an all-solid-state and robust device with no-moving parts that can fast tune their filtered frequency carrier. Such a device is developed by bonding a piezoelectric transducer on a specially cut birefringent crystal. In the LWIR there is a global investigation on efficient solutions for AOTF in future spectral filtering applications. Crystal of mercurous chloride (Hg2Cl2) and mercurous bromide (Hg2Br2) are candidates that demonstrate an advantage in this spectral domain, thanks to a broadband transparency and a fairly large value of their figure of merit M2. Industrial development of those crystals has recently started and presents an excellent opportunity to prospect feasibility of such AOTF development. The purpose of our work is to develop a numerical tool to have a better understanding of the acousto-optic interaction inside mercurous halides crystals. Unfortunately, all the characteristics of those mercurous halides based crystals are not well known nowadays. One important component of the photoelastic tensor is always missing. It implies that the unique interaction configuration that optimizes the diffraction efficiency for a wavelength range can’t be computed analytically with the usual techniques. To overcome this difficulty, we propose a numerical tool based on an acousto-optic interaction and an acoustic wave propagation models. We will also include the AOTF considerations and the theoretical background needed to carry out the filter design.
Optical design and modeling of satellite imaging spectrometer for atmosphere monitoring
Author(s):
Yury Dobrolenskiy;
Ilya Dziuban;
Yuriy Ivanov;
Ivan Syniavskyi;
Dmitry Ionov;
Anatoly Poberovski;
Oleg Korablev;
Anna Fedorova;
Nikita Vyazovetskiy
Show Abstract
We describe a concept of a satellite imaging spectrometer dedicated for monitoring of the Earth atmosphere operating in the visible and near ultraviolet spectral range. The instrument targets measurements of total ozone as well as other gases (nitrogen dioxide, oxygen and its dimer etc). The instantaneous field of view (IFOV) across track reaches 100° allowing to obtain global daily maps of trace gases content when operating from a typical orbit. The optical concept and design of the instrument, which consists of the entrance unit, two spectrometric channels (for two wavelength ranges) and the calibration unit are described. We also discuss the results of the optical modeling, confirming the proposed characteristics: the spectral resolution of 0.3 nm for the range 300 – 400 nm and 0.5 nm for the range 400 – 800 nm. The angular resolution is ~ 0.5° in both channels that corresponds to ~6×6 km area on the Earth surface for nadir direction from a 700-km orbit.
Characterization by OCT of a new kind of micro-interferometric components for the NanoCarb miniature imaging spectrometer
Author(s):
Hélène Ehrhardt;
Silvère Gousset;
Jumana Boussey;
Marie Panabière;
Etienne Le Coarer;
Laurence Croizé;
Yann Ferrec;
Laure Brooker
Show Abstract
In this paper, we describe the NanoCarb concept as well as its key elements. Then we will explain the design of the prototype followed by the development of characterization techniques. Finally, we will present how this tool can be used as part of end-to-end model. The key element of the NanoCarb concept is a matrix of silicon Fabry-Perot microinterferometers, which allows us to perform both imaging and interferometry with a field of view of 18° and several interferometric samples in a snapshot. This technique permits us to optimize the SNR for a much reduced volume. The very complex and unusual design of this component brings huge optical and technological challenges, and requires the development of characterization techniques at the nanometer scale. Upon achievement of this purpose, the next step will be the integration of this matrix in a NanoCarb prototype to demonstrate its effective performances. We present a test bench using the interferential metrology technique of Optical Coherence Tomography (OCT). In a first time, we managed to obtain optical path maps of different silicon wafers with nanometer accuracy. Then, we employed the technique to characterize the first micro-interferometers. In parallel, we realized the first prototype integration of NanoCarb with an InGaAs focal plane array and started its characterization
EnMAP: hyperspectral Imager (HSI) for Earth observation: current status
Author(s):
Martin Mücke;
B. Sang;
B. Heider;
H. -P. Honold;
M. Sornig;
S. Fischer
Show Abstract
The Environmental Mapping and Analysis Program (EnMAP) is a German space borne science mission that aims at characterizing the Earth’s environment on a global scale. The single payload of the satellite is the Hyperspectral Imager (HSI). It is capable of measuring the solar radiance reflected from the Earth’s surface as a continuous spectrum in the spectral range of 420nm to 2450nm, with a spectral sampling of 6.5nm (VNIR) and 10nm (SWIR). The EnMAP swath of 30km is sampled in spatial direction with 30m GSD.
In this proceeding, we give an overview of the design and current integration status of the HSI instrument optical unit with additional focus on measured optical and electro-optical performance.
Traceable radiance source for spectroradiometer calibration
Author(s):
Steven van den Berg;
Paul Dekker;
Tessel van der Laan;
Gerard Otter;
Niels Dijkhuizen;
Bilgehan Gür;
Sanneke Brinkers
Show Abstract
SI traceable calibration of satellite instruments like spectroradiometers get increasingly important in space-based observation for various reasons. First, requirements on measurements in terms of accuracy, dynamic range and wavelength range get increasingly demanding. Second, long term observations require SI traceability for comparability of data records that have been acquired over a long time interval (decades) and with different instruments. In this contribution we outline an approach for radiance calibration of spectroradiometers with a wavelength-tunable radiance source. The radiance source is based on an integrating sphere and a widely tunable laser (UVN-SWIR) and will be calibrated against a set of reference detector standards. By offering the radiance source as a stimulus to the spectroradiometer under test, the instrument can be calibrated for spectral radiance response. Potentially this traceability route could lead to a reduced measurement uncertainty compared to the traditional FEL-lamp based method. Furthermore, other instrument characteristics can also be derived from the same set of measurements, like stray-light effects and the instrument response function.
Novel gratings for astronomical observations
Author(s):
N. Ebizuka;
T. Okamoto;
M. Takeda;
T. Hosobata;
Y. Yamagata;
M. Sasaki;
T. Kamizuka;
I. Tanaka;
T. Hattori;
S. Ozaki;
W. Aoki
Show Abstract
We introduce novel gratings for next generation instruments of the TMT (Thirty Meter Telescope), the 8.2 m Subaru telescope, other ground-based and space-borne telescopes. The reflector facet transmission (RFT) grating which is a surface relief grating with sawtooth shaped grating lattice of an acute vertex angle, is developed for the WFOS of the TMT. The hybrid grism (direct vision grating) for the MOIRCSof the 8.2m Subaru Telescope is developed as a prototype of the RFT grating. The volume binary grating is developed for a high-dispersion echelle grism of the nuMOIRCS as the first light instrument of the ULTIMATE Subaru. We also developing a silicon grism for the MIMIZUKU of the 6.5m telescope of the University of Tokyo Atacama Observatory in Chile and a quasi-Bragg (QB) immersion grating.
Feasibility of a non-redundant pupil mask for in-flight wavelength measurements
Author(s):
Nicola Baccichet;
Lucas Labadie
Show Abstract
The study of sparse aperture masking as a mean to extract spectral information is a relatively little investigated content. However, despite the loss of throughput that comes with this technique, it allows one to benefit from the many advantages brought by interferometry, without the need of complex phase-controlled systems.
In this paper, we analyse the potential of non-redundant aperture masking for spectral measurements, highlighting its capabilities both as a tool for precise single-wavelength metrology, and as alternative to low resolution spectrographs.
Although here presented as a general introduction, this technique is suitable for a large number of potential applications, ranging from compact cube-sat missions for the analysis of bright sources, to large-dish space telescopes where the increased sensitivity allows one to study fainter targets.
Optical compressive sensing technologies for space applications: instrumental concepts and performance analysis
Author(s):
Donatella Guzzi;
Giulio Coluccia;
Demetrio Labate;
Cinzia Lastri;
Enrico Magli;
Vanni Nardino;
Lorenzo Palombi;
Ivan Pippi;
Daniela Coltuc;
Alessandro Zuccaro Marchi;
Valentina Raimondi
Show Abstract
This paper presents the results of a study aimed at investigating the potential of Compressive Sensing (CS) technologies for optical space instruments. Besides assessing the pros and cons for a wide set of proposed instrumental concepts for space applications, the study analyzed in further detail two CS-based instrument concepts, each targeting a specific application: an UV-VIS hyperspectral imager on orbiter for stellar spectro-photometry and a MIR camera for sky observation and real-time detection of Near Earth Objects (NEO). The proposed UV-VIS hyperspectral imager relies on a classical CS approach and addresses the CS reconstruction of the full image in order to implement slitless spectrophotometry of stars. The CS-based MIR camera for NEO detection instead explores a novel approach aiming at information extraction without a prior full reconstruction of the image. Besides outlining the optical design of the instruments, its key elements and a pros and cons analysis of the architecture, this paper presents the performance assessment of these instruments for typical application scenarios by means of simulated data. The results showed that, from the point of view of data reconstruction quality, a good performance can be achieved by the designed instruments in terms of compression ratio (CR) and image reconstruction. In terms of system budgets, the CS architecture offered only some marginal benefits with respect to their traditional counterparts, mainly due to the lack of a compression board. Most advantages are instead provided in terms of downlink requirements and memory buffer.
Characterization of fiber-based slit homogenizer devices in the NIR and SWIR
Author(s):
Simon Amann;
Quynh Duong-Ederer;
Tobias Haist;
Bernd Sierk;
Benedikt Guldimann;
Wolfgang Osten
Show Abstract
In this contribution, an approach for the characterization of various fiber-based slit homogenizer devices in the NIR and SWIR is shown. The devices are to be tested for use in a satellite-based spectrometer for spatial monitoring of anthropogenic greenhouse gases. This leads to the characterization requirement for temporal coherence and spatial incoherence. Speckle noise has to be reduced to a very low level, which is achieved using a fixed diffusor in combination with a rotating diffusor and a tunable (wavelength) laser as well as temporal averaging. Remaining variations due to unwanted interferences at the imager are removed by controlled movement of the sensor with an automated micro positioning stage in combination with image processing. The design, realization and characterization of the measurement breadboard as well as near field homogenization results for different input scenes and polarizations are shown. Additionally, the geometric characteristics and the depolarization effect of the fibers are investigated for a homogeneous input scene. Furthermore, a setup and measurement results concerning the focal ratio degradation of the fibers are presented.
Versatile full aperture illumination OGSE Setup for alignment and end-to-end calibration of the EnMAP hyperspectral image
Author(s):
M. Lettner;
T. Lamour;
L. Polz;
W. Glastre;
E. Compain;
S. Fischer
Show Abstract
The EnMAP hyperspectral Imager (HSI)
1 will allow to acquire Images of the Earth surface in a push broom configuration. 230 wavelength bands between 420nm and 2450nm are simultaneously recorded with a ground resolution of 30m x 30m.
The entire satellite is designed and built by OHB-Systems.
Characterizing and calibrating a state-of-the-art hyperspectral instrument as the EnMAP HSI requires to establish measurement setups that outperform the test object in all relevant performance aspects to achieve the required measurement accuracies.
At the same time technical as well as economical considerations yield to develop measurement equipment that can support multiple use cases throughout the Alignment integration and Test (AIT) Process of the Instrument.
This paper reports on development and commissioning activities of optical ground support equipment (OGSE) for full aperture testing of the EnMAP HSI. Design requirements as well as measured setup performance is reported.
The overall OGSE-system has been set-up and commissioned at OHB in Oberpfaffenhofen. It supports the following measurement cases:
• Double-pass wave front measurement of the HSI-Telescope for alignment to the HSI-Spectrometer Module
• Line of sight characterisation of the HSI with sub-arcsecond accuracy
• Scanning knife edge modulation transfer function (MTF)-Measurement of the HSI in the entire field-of-view
• Spectral response characterisation of the HSI in the entire spectral range with sub-nanometer wavelength accuracy.
The OGSE consists of several modules. The core component, a highly stable diffraction-limited 200 mm Collimator including a movement system and a scene generator was designed and built by Bertin Technologies upon OHB specifications.
Ga-free InAs/InAsSb type-II superlattice (T2SL) photodetector for high operating temperature in the midwave infrared spectral domain
Author(s):
J. -P. Perez;
Q. Durlin;
P. Christol
Show Abstract
We studied Ga-free InAs/InAsSb type-II superlattice (T2SL) in terms of period, thickness and antimony composition as a photon absorbing active layer (AL) of a suitable XBn structure for full mid-wavelength infrared domain (MWIR, 3- 5μm) detection. The SL photodetector structures were fabricated by molecular beam epitaxy (MBE) on n-type GaSb substrate and exhibited cut-off wavelength between 5μm and 5.5μm at 150K. Electro-optical and electrical results of the device are reported and compared to the usual InSb MWIR photodiode.
Lifetime of channel electron multiplier detectors dedicated to plasma instruments for Solar Orbiter and JUICE space missions
Author(s):
A. Fedorov;
J. Rubiella Romeo;
R. Baruah;
A. Grigoriev;
N. André
Show Abstract
Both Solar Orbiter and Jupiter Icy moon Explorer (JUICE) are long-life ESA missions, which should work in extremely difficult space environment. A very high thermal load up to 13 Solar constants will affect Solar Orbiter, and JUICE will experience a high penetration radiation influence in the Jupiter magnetosphere. The plasma packages of these missions, dedicated mostly for detection of low energy (between 1eV and 50 kev) ions and electrons shall accept a very high dynamic range of the incident charged particle flow. All these circumstances motivate us to use the Channel Electron Multiplier (CEM) as detectors in both missions. CEMs are a classical low energy charged particle and X-ray detectors that have been used fore many early space missions. Later, they were forced out by Micro-Channel Plates (MCP), which allow to provide an image of the particle distribution. But for such challenge missions as Solar Orbiter and JUICE we have to come back to CEMs because they 1) less sensible to the penetrating radiation 2) have much wide dynamical range, 3) have much longer lifetime than MCPs. The detector lifetime is, actually, the maximum particles number accumulated by detector until its efficiency becomes too low. And this detector feature is critical for Solar Orbiter and JUICE missions.
To check the lifetime of CEMs, for different thermal conditions also, we have made a dedicated experimental setup. We irradiated several CEM samples by a strong electron flux, continuously measuring the CEM gain and keeping 80°C on the sample. The final total number of events, detected by each CEM was equivalent to 20 years of the continuous operation in space. The experiment has shown the excellent lifetime properties of the CEMs, chosen for the missions
Improved low dark current MWIR/LWIR MCT detectors: first results of ROIC and MCT tests
Author(s):
Holger Höhnemann;
Stefan Hanna;
Ajit Kumar Kalgi;
Dirk Van Aken;
Rashme Sudiwala;
Peter Hargrave;
Werner Gross
Show Abstract
Within the TRP program “Development of Low Dark Current MWIR/LWIR Detectors” ne MCT material was tested with reduced dark current for low photon flux applications. A specific ROIC design was set up within this program to allow a proper characterization of the material and act as a demonstrator for further ROIC derivates. Demonstrator assemblies were prepared and tested.
The poster will highlight the specific design approaches for the ROIC and the MCT. Four different topologies for the input stage on the ROIC were implemented to allow direct assessment of the impact of the design approach. A part of these input stages were designed using radiation hardened cell library. The ROIC doesn’t contain any internal state machine but id fully controlled via a high speed SPI interface driven by an external sequencer.
A test setup will be highlighted. A liquid helium cryostat was prepared to allow dark current measurements in an environment which does not suffer from parasitic radiation sources. The same setup is capable for operation with external illumination and optical filers, which can be moved into the beam.
The detector assemblies are presented. A two-step approach is shown which is initially scanning the performance of the different input topologies. A final detector assembly is selected upon the best performance; final assemblies are shown, the test results will be given on the poster.
TDI CMOS image sensor for Earth Observation
Author(s):
Jérôme Pratlong;
Paul Jerram;
Georgios Tsiolis;
Vincent Arkesteijn;
Paul Donegan;
Laurens Korthout
Show Abstract
The first Earth Observation satellites used linear sensors, which have a significant limitation in the signal that can be gathered in each pixel resulting in a limited ground sampling distance (GSD) in order to achieve the required signal to noise ratio (SNR). The solution to this was to use TDI (Time delay integration) detectors. The first generations of TDI detectors were based on CCDs, which can intrinsically operate in a TDI mode by moving charge within the detector at a rate corresponding to the movement of the satellite over the ground. The CCD technology used relatively large pixels (typically 10-13μm) with low line rate of typically around 10kHz achieving a ground resolution of down to 0.5m with very high SNR. More recent CCD TDI sensors can achieve line rates of up to 30kHz with pixels as small as 7μm but the interfaces become extremely complex and power dissipation is high. Improvements to satellite technology means that a higher resolution is now achievable and this requires higher line rates, over 30kHz and pixel sizes significantly below 7μm as well as more complex sensors with higher numbers of multispectral lines to give improved spectral data. In order to achieve all of these requirements the use of a CMOS sensor with on chip digitization become essential.
The first CMOS approach was to carry the TDI functionality using digital summation. This approach quickly demonstrated limitations in terms of line rate and power consumption as the entire sensor has to be read for every line on the ground that is sampled. More recently CMOS technology has matured the charge domain CCD approach with comparable electro-optical performance to CCDs while offering higher speed, smaller pixel pitch and high level of integration.
This latest technology step has also considerably eased the integration of the sensor into the satellite, opening new opportunities to produce focal planes at significantly lower cost with much reduced power dissipation, size and weight. The challenge has been to establish a CCD on CMOS technology that can obtain a similar full well capacity and charge transfer efficiency (CTE) performance to CCDs. This CCD on CMOS technology has now reached the point where the performance is comparable to CCDs but with very much lower operating voltages.
This paper will present the evolution of earth scanning image sensors with a focus on the latest TDI CMOS technology including the recent results obtained with the latest CMOS technology using TDI in charge domain approach. These results will include FWC, CTE, radiation performance as well as results from very high speed, up to 3.6Gbps output stream, and highly integrated readout circuitry.
Finally we will provide details of new devices that will provide performance that would not have been possible with CCDs.
Differential gain stability of a microchannel plate detector dedicated to a neutral particle instrument (JENI) of the JUICE space mission
Author(s):
A. Grigoriev;
A. Fedorov;
N. André;
O. Chassela;
E. Le Comte
Show Abstract
The Jupiter Icy moon Explorer (JUICE) is a long-life ESA mission to be working in extremely harsh space environment. The energetic neutral atoms imager (JENI), designed as a Time-of-Flight (TOF) spectrometer, contains microchannel plate (MCP) detectors to register start and stop secondary electrons produced by incident neutrals atoms. Due to rather severe mass and power constraints this spectrometer uses a single MCP assembly to detect both Start and Stop electrons, to define their detection time and then calculate an incident particle velocity. Thus one MCP is divided in several sectors. One of them is dedicated to detect Start electrons and another sector is detecting Stop electrons. Since the load of the Start sector can be higher than the load of the Stop sector by a factor of 10, it is important to know how does the MCP sectoral gain (Differential Gain) change during the MCP lifetime. Since the JUICE mission is a long-time mission it is important to be sure the MCP gain changes evenly along the active surface. To characterize the MCP overall gain uniformity we have combined the gain uniformity measurement and differential gain stability measurement into a single experiment of the MCP aging. A differential gain stability test has been performed on a representative MCP assembly using a uniform UV light source. The differential UV exposure has been achieved using an attenuation mask provided ~10% exposure of a majority of the MCP surface and full exposure of a small area. Differential gain versus the MCP bias voltage has been characterized every 0.5 C/cm2 of the charge extracted out of the MCP. We have shown the spatial gain variations and the differential degradation of the MCP sectors are acceptable for JENI experiment.
Type-II superlattices: a promising material for space applications
Author(s):
V. Daumer;
F. Rutz;
A. Wörl;
J. Niemasz;
R. Müller;
T. Stadelmann;
R. Rehm
Show Abstract
Type-II superlattices (T2SLs) are currently recognized as the sole material system offering comparable performance to HgCdTe, yet providing higher operability, stability over time, spatial uniformity, scalability to larger formats, producibility and affordability. Hence, T2SL technology is very promising for space applications. Fraunhofer IAF played a vital role in the development of III-As/Sb T2SLs right from the beginning. Mono- and bi-spectral focal plane arrays up to 640×512 pixels for the mid- and long-wavelength infrared (IR) have been demonstrated. The growth of T2SL is performed by molecular beam epitaxy (MBE) in multi-wafer reactors. We report on the excellent homogeneity and reproducibility of the growth process, established in the past years at Fraunhofer IAF. After processing this material to detector arrays, the T2SL detectors have been characterized down to low temperatures (below 40K) with promising properties regarding the dark current. For MWIR and LWIR detectors the resolution limit of the measurement setup with a dark current density of 2×10-10 A/cm2 has been reached at 77 K and 36 K, respectively.
Miniature diode spectrometer design
Author(s):
A. Atvars;
S. Khudaverdyan;
M. Lapkis;
S. Rudenko
Show Abstract
Standard spectrometers involve prisms or diffraction grating to expand light spectra in space and then each spectral region is measured with a photodetector. The limit for miniaturization of such spectrometers is determined by space allocation for spectra expansion. This limit can be overcome with a proposed spectrometer design which employs the dependence of light penetration depth in semiconductor on spectral wavelength and consumes no need for optical components (prisms or diffraction grating). The principle is realized by silicon semiconductor structure with oppositely directed Schottky barrier and n-p junction, where n-region is the base. By applying external voltage U ( − 1V … + 1V) on this structure, the minimum of the potential is formed in some depth x = x(U) of the semiconductor. The observed photocurrent I = I(U) depends on the integral radiation flux that penetrated the material deeper than x. Absorption coefficient ∝(λ) decreases as λ increases. Therefore by scanning the depth x, the contribution of different radiation components (with different λ) on the final signal is scanned. When Current-Voltage dependence I(U) is observed, a special algorithm can be used to extract the initial radiation spectra from these data. Proposed photodetector-spectrometer has the observation spectral range of 400 - 1100 nm. Reconstructed spectra show the accuracy for the spectral peak determination of 20 - 100 nm. Directions for improvements of the design and calculation algorithm is presented.
On-sky performance verification of near infrared eAPD technology for wavefront sensing at ground based telescopes, demonstration of e-APD pixel performance to improve the sensitivity of large science focal planes and possibility to use this technology in space
Author(s):
G. Finger;
Ian Baker;
D. Alvarez;
F. Eisenhauer;
G. Hechenblaikner;
D. Ives;
L. Mehrgan;
M. Meyer;
J. Stegmeier;
H. J. Weller
Show Abstract
Ground based near infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry required the development of high-speed sensors. Because of the high speed, a large analog bandwidth is needed. The short exposure times result in small signal levels which require noiseless detection. Both of these conflicting requirements cannot be met by state-of-the-art conventional CMOS technology of near infrared arrays as has been attempted previously[1][2]. The HgCdTe electron avalanche photo diode (eAPD) technology is the only way to overcome the limiting CMOS noise barrier of near infrared sensors. Therefore, ESO funded the development of the near infrared SAPHIRA 320x256 pixel e-APD arrays at LEONARDO [3][4][5][6][7]. SAPHIRA arrays have now become the devices of choice for control loops with unsurpassed performance [21]. This has also been demonstrated by the four wavefront sensors and the fringe tracker deployed in the VLTI instrument GRAVITY which set a new sensitivity standard in infrared interferometry [8][9]. It has also been demonstrated that APD arrays have extremely low dark current (1E-3 electrons/s/pixel) and may outperform conventional CMOS arrays for 100 second integrations when operated with moderate APD gains. For AO systems of extremely large telescopes and for co-phasing segmented mirror telescopes larger formats are needed. Therefore, a 512x512 pixel SAPHIRA array with 64 parallel video outputs optimized for pyramid wavefront sensing is in development. Since the SAPHIRA array has successfully passed radiation hardness testing it soon may be used for future instruments in space. Apart from the large array common voltage for high APD gain it can also be operated with voltages compatible with the space qualified SIDECAR ASIC [10].
Investigation on a SmallSat CMOS image sensor for atmospheric temperature measurement
Author(s):
Jilin Liu;
Tom Neubert;
Denis Froehlich;
Peter Knieling;
Heinz Rongen;
Friedhelm Olschewski;
O. Wroblowski;
Qiuyu Chen;
Ralf Koppmann;
Martin Riese;
Martin Kaufmann
Show Abstract
This article presents the characterization and analysis of a commercial off-the-shelf (COTS) CMOS detector utilized in a miniaturized satellite payload for atmospheric temperature measurements. To evaluate the performance of the selected CMOS detector, a series of tests were performed. The temperature dependent dark current, the readout noise and the system gain are determined, which are provided for the subsequent system performance evaluation and data processing. A case study is established to simulate the space radiation effect to determine the needed shielding thickness on the instrument. The effect of radiation damage on the CMOS image sensors is investigated using a Co-60 Gamma radiation source.
Detection efficiency of micro channel plates and channel electron multiplier detectors to penetrating radiation in Space
Author(s):
N. André;
A. Fedorov;
O. Chassela;
A. Grigoriev;
E. Le Comte;
J. Rouzaud;
M. Bassas
Show Abstract
Space-based instruments for detection of photons, plasma, and energetic neutral atom imaging include electron multiplier detectors that are subject to increased transient noise, long-term degradation and even potential failure due to the substantial fluxes of high-energy particles that penetrate the instrument in the space environment. The most commonly used electron multiplier detectors are Multi-Channel Plate (MCP) and Channel Electron Multiplier (CEM). These detectors are sensitive not only to the incident energetic charged particles themselves but they are also sensitive to the final end-product energy deposited by energetic electrons, ions, and X-rays. The resulting radiation-induced background noise can potentially swamp the science signal. This issue constitutes undoubtedly the main challenge for particle instruments onboard future missions to Jupiter like the European Space Agency Jupiter ICy moon Explorer (JUICE), and requires dedicated and innovative radiation mitigation techniques (e.g., multiple coincidence, anti-coincidence) far beyond the simple passive shielding techniques commonly used to protect electronics and other subsystems against Total Ionizing Dose (TID). The accurate response (i.e., efficiency) of MCPs and CEMs detectors against high-energy particles is however not well known, with limited estimates available in the literature. This makes it complicated in particular to reliably predict the Signal to Noise ratio of the instrument, and, hence, ensure that the instrument will return useful scientific data when operated in the Jovian magnetosphere. Here, we first use real measurements from the Galileo Plasma spectrometer (PLS) instrument to derive the background noise measured by CEMs in the Jovian environment. These measurements are used in combination with Geant4 simulations in order to estimate the efficiency of CEMs against high-energy electrons. We then present the results of an experiment in which we measured and compared the response of MCP and CEM detectors to keV-MeV electrons and keV X-rays using a Van de Graff electron gun available at ONERA, Toulouse, France. These experimental tests were funded by the french space agency CNES in support of the JUICE mission and in particular for the contribution of the Institut de Recherche en Astrophysique et Planétologie to the Particle Environment Package (PEP).
Introducing the atmospheric thermodynamics lidar in Space: ATLAS
Author(s):
Paolo Di Girolamo;
Andreas Behrendt;
Volker Wulfmeyer;
Adolfo Comerón;
Philippe Keckhut;
Alain Hauchecorne;
Evelyne Richard;
Franco Marenco;
Geraint Vaughan;
Mathias Rotach;
Roland Potthast;
Alan Geer;
Belay B. Demoz;
Joseph Santanello;
David N. Whiteman;
David D. Turner
Show Abstract
Our understanding of the distribution of heat and water in the atmosphere still shows critical gaps on all temporal and spatial scales. This is mainly due to a lack of accurate measurements of water vapor and temperature profiles - hereafter called thermodynamic (TD) profiles - with high vertical and temporal resolution, especially in the lower troposphere. Accurate, high temporal-spatial resolution observations of TD profiles are essential for improving weather forecasting and re-analyses, for studying land-atmosphere feedback processes and for improving model parameterizations of landsurface and turbulent transport processes in the Atmospheric Boundary Layer. These observational gaps can be addressed with a new active remote sensing system in space based on the Raman lidar technique. Combining vibrational and rotational Raman backscatter signals, simultaneous measurements of water vapour and temperature profiles and a variety of derived variables are possible with unprecedented vertical and horizontal resolution, especially in the lower troposphere. This is the key concept of ATLAS, which was submitted in March 2018 to the European Space Agency in response to the Call for Earth Explorer-10 Mission Ideas in the frame of ESA EOEP. An assessment of the expected performance of the system and the specifications of the different lidar sub-systems has been performed based on the application of an analytical simulation model for space-borne Raman lidar systems. Results from the simulations and technical aspects of the proposed mission will be illustrated at the conference.
The evanescent wave coronagraph project: development status and potential for space based observations
Author(s):
Mary Angelie Alagao;
Christophe Buisset;
Thierry Lépine;
Eric Thiébaut;
Maud Langlois;
Michel Tallon;
Isabelle Tallon-Bosc;
Yves Rabbia;
Saran Poshyachinda;
Boonrucksar Soonthornthum
Show Abstract
The Evanescent Wave Coronagraph (EvWaCo) is a coronagraph with an occulting mask based on the frustration of total internal reflection to i) produce an achromatic extinction of the central star and ii) reveal the faint companion surrounding the star. Results obtained in laboratory conditions show contrast performance of a few 10
-6 between 10 λ
C/D and 20 λ
C/D over the full I-band centered at the wavelength λ
C = 800 nm with a spectral ratio of Δλ/ λ
C ≈ 20% in unpolarized light.
In this paper, we discuss the advantages of using EvWaCo to observe and characterize exoplanets with a space-based telescope. In the first section, we describe the system and present the current results obtained with the EvWaCo testbed. We also illustrate the capability of this coronagraph to detect the companion 30,000 times (respectively, 100,000 times) fainter than the central star at distances equal to 15 Airy radii (respectively, 30 Airy radii) from the PSF center in polychromatic and unpolarized light.
In the second section, we describe the design of the prototype dedicated to the on-sky tests of the instrument with the 2.4 m Thai National Telescope at horizon 2020. This prototype has been designed with the objective to reach a contrast equal to a few 10
-4 at the inner working angle (IWA) equal to 3 λ/D from the star PSF center while observing through the atmosphere over the full photometric I-band. This prototype will include an adaptive optics specified to reach at λ ≈ 800 nm a Strehl ratio > 0.8 for magnitude m < 7.
In the third section, we show the theoretical performance of EvWaCo: a contrast comprised between a few 10
-6 and 10
-7 in the I-Band between 3 λ/D and 10 λ/D in the I-Band for an IWA equal to 3 λ/D with a Gaussian apodization in unpolarized light. We also show that similar contrasts performance are obtained in the V-, R-, bands, thus illustrating the EvWaCo quasi-achromaticity. Finally, we discuss the advantages and the limitation using the proposed concept for space-based observations and spectral characterization of exoplanets.
Validation of a spatial light modulator for space applications
Author(s):
Manuel Silva-López;
Antonio Campos-Jara;
Alberto Álvarez-Herrero
Show Abstract
Liquid crystals on silicon spatial light modulator (LCOS-SLM) combine the potential of reflection type spatial light modulators with the compactness and robustness of a single chip. They are used today for beam steering applications, optical beam shaping and laser processing. These devices have a high potential for space applications due to the fact that they allow to introduce any tailored wavefront distortion in an imaging instrument. Then, image reconstruction methods as phase diversity can be used to determine the Point Spread Function (PSF) inflight and, later, to introduce a corrective wavefront distortion to correct possible deviations of the expected optical quality.
Among other aberrations, the beam phase control can act on the level of focus. In space optical applications image refocusing is usually performed by means of mechanisms, either by using linear displacement of lenses or rotating wheels with plates with different thicknesses. The compactness and absence of mechanical parts of LCOS-SLM can be of great advantage for these applications. LCOS-SLM can save complexity and weight. It also reduces the risk associated to the wear of moving parts.
However, this technology has not been qualified for space applications. Liquid crystal leaks as well as outgassing issues may result as a consequence of a low pressure environment. Thermal issues can also result in loss of device homogeneity and the radiation tolerance should be analyzed. In any case, an exhaustive space simulation test is mandatory to increase the Technological Readiness Level of these devices for their use in space systems.
In our work we are showing preliminary test of a commercial LCOS-SLM under thermo-vacuum conditions. These tests are basic calibrations used to evaluate performance and degradation in a simulated space environment. Different calibration procedures are also discussed. This technology, with potential to greatly simplify an instrument design, was included in a proposal for the instrument IMaX+ spectro-polarimeter, to be onboard the mission Sunrise III, within the NASA Long Duration Balloon program.
VNIR and SWIR FPA designs for 3MI instrument: thermal, mechanical and dimensional stability challenges
Author(s):
Xavier Chauffleur;
Gilles Marque;
Antoine Weickman;
Catherine Delelis;
Carlos Carvalos;
Salem Belmana;
Alain Durieux;
Serge Primet
Show Abstract
Within the framework of the 3MI instrument for METOP-SG satellite, Sodern develops the Focal Plane Assemblies (FPAs) for the SWIR and VNIR detectors. The main functions of these FPAs are the thermal cooling, the dimensional stability of the detectors and the mechanical withstanding with respects to the thermal and mechanical environments. From a mechanical point of view, the mechanical requirements are identical for the two FPAs with notably stiffness above 500Hz. On the other hand, from a thermal point of view, the temperature environment and thermal control principle between SWIR and VNIR FPAs are different by the use of a heater for SWIR and a TEC for VNIR. At last, the SWIR FPA turns out to be the more challenging case with a high insulation, up to 200K/W, between cold parts (-90°C) and hot interface (25°C) and also a high coupling of 2.7K/W with the cold sink. This paper shows how a single architecture composed of a hexapod structure made of 6 titanium shafts and a thermal strap made of low diameter copper strands permits to achieve the best compromise between thermal and mechanical requirements for both FPAs. In addition to technical aspects, this common architecture also answers to the aim of cost cutting for the different phases of the project: design sharing, grouping of supplies, mutual qualification tests, shared integration tools and processes. Several models have been integrated and tested to verify the performances and the withstanding to thermal and mechanical environments.
High performance large lightweight mirrors fabrication adapted to stress-mirror polishing (SMP) technique
Author(s):
S. Lemared;
M. Ferrari;
T. Dufour;
C. Du Jeu;
E. Hugot;
G. R. Lemaitre
Show Abstract
Earth observation space instruments require very tight optical performances in the most stringent configuration (observation in the optical wavelengths range). The optical quality of mirrors, mainly in term of both shape and roughness polishing quality, has to reach very tight specifications down to a few nanometers. In this paper, we present a new manufacturing process, based on Stress-Mirror Polishing (SMP) technique, dedicated to lightweight mirrors aspherisation. We consider specific features or constraints due to the structure of the honeycomb, while reducing footprint effects and inhomogeneous surface effects. We also identify the most efficient way to correct and/or anticipate these issues taking into account industrial constraints on real-scale mirrors. In this new process, both SMP technique and lightweight design have to be optimized.
The design and assembly of a long-focal-length telescope with aluminum mirrors
Author(s):
Shenq-Tsong Chang;
Yu-Chuan Lin;
Chun-Chieh Lien;
Ting-Ming Huang;
Ho-Lin Tsay;
Jiun-Jih Miau
Show Abstract
Three-mirror-anastigmat (TMA) telescopes have been widely used in long-focal length payloads especially in space due to its excellent features for correcting aberrations, wide spectral range and shorter physical requirement. This paper describes the assembly results of the telescope that may be used in the payload of Formosat-5 follow-on mission. The telescope was a pathfinding one that was designed according to the target specifications of National Space Organization. Optical design is of Korsch type with three mirrors in the system, which is different from that in Formosat-5 RSI. Mechanical design and assembly procedures require modification from those of Formosat-5 accordingly. focal length of the telescope was 7714 mm and F-number 14. Diamond-turned aluminum mirrors were adopted due to time and budget constraint. Barrel was selected as structure configuration between primary and secondary mirrors, while struts were designed to support the tertiary mirror. A main plate was used to connect the barrel and struts. Analysis of the structure has been performed.
Study and realization of a prototype of the primary off-axis 1-m diameter aluminium mirror for the ESA ARIEL mission
Author(s):
Vania Da Deppo;
Emanuele Pace;
Gianluca Morgante;
Mauro Focardi;
Marco Terraneo;
Fabio Zocchi;
Giovanni Bianucci;
Giuseppina Micela
Show Abstract
ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) has been selected by ESA as the next mediumclass science mission (M4) to be launched in 2028. The aim of the ARIEL mission is to study the atmospheres of a selected sample of exoplanets.
The payload is based on a 1-m class telescope ahead of a suite of instruments: two spectrometric channels covering the band 1.95 to 7.80 μm and four photometric channels working in the range 0.5 to 1.9 μm.
The production of the primary mirror (M1) is one of the main technical challenges of the mission. A trade-off on the material to be used for manufacturing the 1-m diameter M1 was carried out, and aluminium alloys have been selected as the baseline materials both for the telescope mirrors and structure. Aluminium alloys have demonstrated excellent performances both for IR small size mirrors and structural components, but the manufacturing and thermo-mechanical stability of large metallic optics still have to be demonstrated especially at cryogenic temperatures.
The ARIEL telescope will be realized on-ground (1 g and room temperature), but it shall operate in space at about 50 K. For this reason a detailed tolerance analysis was performed to assess the telescope expected performance.
M1 is an off-axis section of a paraboloidal mirror and will be machined from a single blank as a stand-alone part. To prove the feasibility of such a large aluminium mirror, a pathfinder mirror program has been started. The prototype has been realized and tested, so far at room temperature, by Media Lario S.r.l.. Cryogenic testing of the prototype will be performed during Phase B1.
Electro-optical performance of the Ingenio/SEOSAT primary payload
Author(s):
C. Miravet;
G. Taubmann;
G. Santos;
D. Zorita;
I. Cabeza;
A. Marini;
F. Reina;
A. Popescu
Show Abstract
Ingenio/SEOSAT is a high-spatial-resolution optical mission developed under the Spanish Earth Observation National Program for Satellites (PNOTS), and managed technically in the framework of an ESA contract. It features as Primary Payload (PP) a high-resolution optical payload with one 2.5 meter resolution panchromatic channel and four 10 meter resolution visible/near infrared spectral channels. It is based on a twin Korsch telescope concept, each telescope covering half of the instrument’s swath width. At the present stage, the principal payload has undergone the vibration and environmental tests, and the final performance test campaign has been completed successfully. In this communication, we will present the main measured optical performance parameters, and its relation to predictions obtained from the different computer models. First, the payload’s geometric performance is addressed in the paper, with focus on parameters such as the spatial sampling angle, detection line angle and distortion. On a second group, wavefront error and modulation transfer function are reviewed. Finally, radiometric performance is considered, with parameters such as radiance saturation levels and signal-to-noise ratios at defined minimum and reference radiances. All instrument performances have been measured at Thales Alenia Space in Cannes with set-ups developed specifically by Thales Alenia Space for Ingenio/SEOSAT ( i.e. Modulation Transfer function, straylight and radiometric measurements).
WFIRST OAPs' fabrication: prototyping phase
Author(s):
Mélanie Roulet;
Emmanuel Hugot;
Carolyn Atkins;
Sabri Lemared;
Marc Ferrari;
Simona Lombardo
Show Abstract
This paper describes the development of a new manufacturing process to directly obtain off-axis parabolas (OAP) by combining 3D printing and stress polishing. 3D printing opens up a new vision for optics fabrication by providing innovative lightweight structures which are not fabricable with traditional mechanical manufacturing. It also provides a new range of materials covering plastic up to metal through composite materials and ceramics.
The direct imaging of exoplanets using coronagraphic instruments provides a good example of an astronomical application that can greatly benefit from such developments. Exoplanets imaging is very demanding in terms of optical surface quality, however, the majority of coronagraphic instruments use off axis optics, which manufacturing of such optics could present some drawbacks: either the optics are cut out of a parent large mirror, resulting in a material loss, or the surfaces are machined with sub-aperture tools, resulting in high spatial frequency ripples which must be avoided for this application.
Thanks to 3D printing and topology optimisation we created an innovative warping harness design which can generate any off axis parabola shapes with only one actuator. We optimised the harness thickness distribution in order to reach non symmetrical deformation composed of astigmatism and coma. The warping is applied by micrometric screws and the high transmission factor of the system allows to keep stable the final error budget despite the error introduced by the warping harness fabricated by 3D printing. Several warping harness designs and materials were explored for the prototyping phase. This study is part of WFIRST satellite which will be launch in 2024 by NASA to observe galaxies via a wide field instrument and also perform exoplanet direct imaging via coronagraph. In the case of the WFIRST coronagraphic instrument, eight off axis parabolas are used to relay the beam from one pupil to another. We present the first prototyping results dedicated to the WFIRST off axis parabolas. Deformation surface results are performed by interferometric measurements and compared to Finite Element Analysis predictions.
Optical performance of the Metis coronagraph on the Solar Orbiter ESA mission
Author(s):
Fabio Frassetto;
Vania Da Deppo;
Paola Zuppella;
Marco Romoli;
Silvano Fineschi;
Ester Antonucci;
Giana Nicolini;
Giampiero Naletto;
Piergiorgio Nicolosi;
Daniele Spadaro;
Vincenzo Andretta;
Marco Castronuovo;
Marta Casti;
Gerardo Capobianco;
Giuseppe Massone;
Roberto Susino;
Federico Landini;
Maurizio Pancrazzi;
Luca Teriaca;
Udo Schühle;
Klaus Heerlein;
Michela Uslenghi
Show Abstract
The Metis coronagraph aboard the Solar Orbiter ESA spacecraft is expected to provide new insights into the solar dynamics. In detail, it is designed to address three main questions: the energy deposition mechanism at the poles (where the fast wind is originated), the source of the slow wind at lower altitude, and how the global corona evolves, in particular in relation to the huge plasma ejections that occasionally are produced. To obtain the required optical performance, not only the Metis optical design has been highly optimized, but the alignment procedure has also been subjected to an accurate evaluation in order to fulfill the integration specifications. The telescope assembling sequence has been constructed considering all the subsystems manufacturing, alignment and integration tolerances. The performance verification activity is an important milestone in the instrument characterization and the obtained results will assure the fulfillment of the science requirements for its operation in space.
The entire alignment and verification phase has been performed by the Metis team in collaboration with Thales Alenia Space Torino and took place in ALTEC (Turin) at the Optical Payload System Facility using the Space Optics Calibration Chamber infrastructure, a vacuum chamber especially built and tested for the alignment and calibration of the Metis coronagraph, and suitable for tests of future payloads.
The goal of the alignment, integration, verification and calibration processes is to measure the parameters of the telescope, and the characteristics of the two Metis channels: visible and ultraviolet. They work in parallel thanks to the peculiar optical layout. The focusing and alignment performance of the two channels must be well understood, and the results need to be easily compared to the requirements. For this, a dedicated illumination method, with both channels fed by the same source, has been developed; and a procedure to perform a simultaneous through focus analysis has been adopted.
In this paper the final optical performance achieved by Metis is reported and commented.
PILOT optical alignment
Author(s):
B. Mot;
G. Roudil;
Y. Longval;
P. Ade;
Y. André;
J. Aumont;
L. Baustista;
J. -P. Bernard;
N. Bray;
P. de Bernardis;
O. Boulade;
F. Bousquet;
M. Bouzit;
V. Buttice;
A. Caillat;
M. Charra;
M. Chaigneau;
B. Crane;
J. -P. Crussaire;
F. Douchin;
E. Doumayrou;
J. -P. Dubois;
C. Engel;
P. Etcheto;
P. Gélot;
M. Griffin;
G. Foenard;
S. Grabarnik;
P. Hargrave;
A. Hughes;
R. Laureijs;
Y. Lepennec;
B. Leriche;
S. Maestre;
B. Maffei;
J. Martignac;
C. Marty;
W. Marty;
S. Masi;
F. Mirc;
R. Misawa;
J. Montel;
L. Montier;
J. Narbonne;
J. -P. Nicot;
F. Pajot;
G. Parot;
E. Pérot;
J. Pimentao;
G. Pisano;
N. Ponthieu;
I. Ristorcelli;
L. Rodriguez;
M. Salatino;
G. Savini;
O. Simonella;
M. Saccoccio;
P. Tapie;
J. Tauber;
J. -P. Torre;
C. Tucker
Show Abstract
PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloonborne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy. The PILOT instrument allows observations at wavelengths 240 μm and 550 μm with an angular resolution of about two arcminutes. The observations performed during the two first flights performed from Timmins, Ontario Canada, and from Alice-springs, Australia, respectively in September 2015 and in April 2017 have demonstrated the good performances of the instrument. Pilot optics is composed of an off axis Gregorian type telescope combined with a refractive re-imager system. All optical elements, except the primary mirror, which is at ambient temperature, are inside a cryostat and cooled down to 3K. The whole optical system is aligned on ground at room temperature using dedicated means and procedures in order to keep the tight requirements on the focus position and ensure the instrument optical performances during the various phases of a flight. We’ll present the optical performances and the firsts results obtained during the two first flight campaigns. The talk describes the system analysis, the alignment methods, and finally the inflight performances.
On-orbit alignment and wavefront compensation of segmented aperture telescope using adaptive optics
Author(s):
Norihide Miyamura
Show Abstract
For small satellite remote sensing missions, a large aperture telescope more than 400mm is required to realize less than 1m GSD observations. However, it is difficult or expensive to realize the large aperture telescope using monolithic primary mirror with high surface accuracy. A segmented mirror telescope should be studied especially for small satellite missions. We describe the conceptual design of the optical system that involve the segmented primary mirror and adaptive optics system, then we show numerical simulation results of the optical performance.
A lightweight Schmidt space telescope configuration for ultra-high energy cosmic ray detection
Author(s):
Vania Da Deppo;
Paolo Sandri;
Piero Mazzinghi;
Alessandro Zuccaro Marchi
Show Abstract
One of the most challenging open questions of modern astrophysics and particle physics is the determination of the origins and the production mechanisms of the Ultra-High Energy Cosmic Rays (UHECR), i.e. particles with energy above the Greisen–Zatsepin–Kuzmin (GZK) limit, which is about 5×10
19 eV.
UHECRs can be studied in two ways: either via direct detection of the secondary particles, i.e. extensive air shower (EAS), produced by UEHRCs interaction with the atmosphere, or by observing during night the track of the UV fluorescence emitted by EAS. The origin direction of the cosmic rays can be therefore determined.
While ground-based observatories are already operative, different optical configurations, based mainly on the Schmidt camera layout or double Fresnel lenses concept, can be envisaged for future space-based ones. Both solutions faced in the past technological issues: transmission and resolution at large field angles for Fresnel lenses and weight of the primary mirror for the Schmidt. However, recent advances in the technology of ultra-lightweight, large and deployable active mirrors made the Schmidt camera approach feasible, becoming the preferred option.
This work describes a lightweight Schmidt space telescope design for UHECRs detection conceived for a mission intended to orbit at 600 km altitude.
The instrument concept is a fast, high-pixelized, large aperture and large Field-of-View (FoV) digital camera, working in the near-UV wavelength range with single photon counting capability. The telescope will record the track of an EAS with a time resolution of 2.5 μs and a spatial resolution of about 0.6 km (corresponding to ~ 4’), thus allowing the determination of energy and direction of the primary particles.
The proposed design has about 50° FoV and a 4.2 m entrance pupil diameter. The mirror is 7.5 m in diameter, it is deployable and segmented to fit the diameter of the considered launcher fairing (i.e. Ariane 6.2). The Schmidt corrector plate is a lightweight annular corona.
This configuration provides a polychromatic angular resolution less than 4' RMS over the whole FoV with a very fast relative aperture, i.e. F/# 0.7. Thanks to its very large pupil and large FoV, the design could be fit for a space-based observatory, thus enhancing the science achievable with respect to the presently operating ground-based counterparts, such as Telescope Array and Auger. A key advantage of this catadioptric design over the classic all refractive adopted in the past is the higher attainable global throughput. This parameter guarantees to reach and fulfil the required instrument photon collection specifications.
Electro-mechanical deformable mirror for space application
Author(s):
Sébastien Theis;
Laurent Ropert;
Vincent Costes;
Laurent Cadiergues;
Paul Sauvageot
Show Abstract
ACMAS program, in partnership with CNES and DGA, intends to develop an innovative concept of deformable mirror (DM) for next generation space telescopes, to manufacture an engineering model and to test it on optical and mechanical points of view.
The design of this space compatible DM is based on ISP System’s technology, and is adapted to space constraints (ECSS) particularly in terms of vibrations and reliability. These electro-mechanical DMs offer some innovative characteristics for space telescopes with low speed wavefront variations.
A specific version of the patented AME actuator is developed for space applications, and tested to TRL6. The deformable mirror’s actuators pattern is optimized in terms of quantity and position with respect to the wavefront corrections expected to apply during mission. The DM design is optimized thanks to finite element modeling in order to withstand the vibrations and shocks due to launching, and improve thermo-mechanical stability, and an innovative redundancy method is developed.
The performance of an engineering model is measured using an optical test bench with high resolution wavefront sensor. The correction thermal stability is also measured and the performance with one and two disabled actuators is evaluated. Vibrations are then injected into the DM. All these measures are compared to simulation values and show an impressive correlation..
Common interface visible sensor
Author(s):
R. Shivitz
Show Abstract
The Lockheed Martin Optical Payload Center of Excellence (OPCoE) collaborated with government customers and leading companies in the aerospace and optics industries to field a space imaging instrument, achieving multi-spectral, wide field, high resolution imaging capability in a compact, lightweight, all reflective architecture. The heart of the instrument is an unobscured three mirror anastigmat collimator. The afocal design consists of a physical entrance pupil accepting a collimated input, an intrinsic internal focus and pupil, and in a compact folded geometry to achieve a balance between critical sampling, radiometric sensitivity, and field of view. Light-weighted, thermally stable materials and robust coatings coupled with low stress, thermal and dynamically stable optical mounts have demonstrated diffraction limited performance during test and over predicted mission conditions. Metrology features were made a central part of the optical component design to facilitate the use of spatial analysis tools and alignment techniques for merit function prescription optimization. The optical components are mounted to a composite egg crate bench, designed to reduce structural mass while ensuring rigid alignment of the optical components. Active thermal control reduces diurnal variations to the optical alignment and ensures stable optical performance. Design innovations include a filter wheel assembly designed to minimize exported force and torque and an internal radiometric calibrator based on high reliability light emitting diodes for focal plane gain calibration. The instrument currently hosts a large format staring focal plane for wide field imaging, but the flexibility of the design can accommodate various sensor packages.
European and US technologies enable CETUS: an ultraviolet space telescope concept
Author(s):
Tony Hull;
Sara Heap;
Bill Danchi;
Bob Woodruff;
Steve Kendrick;
Lloyd Purves
Show Abstract
NASA has funded the Cosmic Evolution Through Ultraviolet Spectroscopy (CETUS) mission study in preparation for the Decadal Survey, ASTRO2020. CETUS is developed as a Probe Class Mission, a new NASA category for astrophysics cost capped at 1B USD. This enables larger and more sophisticated observatories than under NASA’s Explorer Programs, but less ambitious than under NASA Flagship Missions. The NASA CETUS Study has resulted in a wide-field-of-view (WFOV) telescope of 1.5m aperture, with the colleting area by solid angle product A*Ω substantially higher than that for HST. CETUS will include a wide field camera, a multi-object spectrograph of the same field, and also a point source spectrometer reaching down to 100nm wavelength.
Alignment procedure for the Gregorian telescope of the Metis coronagraph for the Solar Orbiter ESA mission
Author(s):
Vania Da Deppo;
Sergio Mottini;
Giampiero Naletto;
Fabio Frassetto;
Paola Zuppella;
Mewael G. Sertsu;
Marco Romoli;
Silvano Fineschi;
Ester Antonucci;
Gianalfredo Nicolini;
Piergiorgio Nicolosi;
Daniele Spadaro;
Vincenzo Andretta;
Marco Castronuovo;
Marta Casti;
Gerardo Capobianco;
Giuseppe Massone;
Roberto Susino;
Federico Landini;
Maurizio Pancrazzi;
Chiara Casini;
Luca Teriaca;
Michela Uslenghi
Show Abstract
Metis is a solar coronagraph mounted on-board the Solar Orbiter ESA spacecraft. Solar Orbiter is scheduled for launch in February 2020 and it is dedicated to study the solar and heliospheric physics from a privileged close and inclined orbit around the Sun. Perihelion passages with a minimum distance of 0.28 AU are foreseen.
Metis features two channels to image the solar corona in two different spectral bands: in the HI Lyman ∝ at 121.6 nm, and in the polarized visible light band (580 – 640 nm). Metis is a solar coronagraph adopting an “inverted occulted” configuration. The inverted external occulter (IEO) is a circular aperture followed by a spherical mirror which back rejects the disk light. The reflected disk light exits the instrument through the IEO aperture itself, while the passing coronal light is collected by the Metis telescope. Common to both channels, the Gregorian on-axis telescope is centrally occulted and both the primary and the secondary mirror have annular shape.
Classic alignment methods adopted for on-axis telescope cannot be used, since the on-axis field is not available. A novel and ad hoc alignment set-up has been developed for the telescope alignment.
An auxiliary visible optical ground support equipment source has been conceived for the telescope alignment. It is made up by four collimated beams inclined and dimensioned to illuminate different sections of the annular primary mirror without being vignetted by other optical or mechanical elements of the instrument.
Liquid crystal phase modulator integration on the TriPleX photonic platform
Author(s):
K. Wörhoff;
A. Ryabchun;
M. Hoekman;
J. Epping;
R. Grootjans;
A. Leinse
Show Abstract
Technology integration of liquid crystal cells for electro-optic modulation has been implemented on the commercial TriPleX photonic platform. Design and fabrication procedure have been optimized for fulfilling the low insertion loss criterion for applications such as space communication and enabling the implementation of compact liquid crystal tuning elements for achieving high integration density. First performance testing of this concept has confirmed low-power consumption switching with 2π phase tuning being obtained within a voltage range of 2.5 V.
Photonic integrated circuits for ultra-fast steering in phased-array antennas
Author(s):
Francesco Amato;
Giovanni Serafino;
Filippo Scotti;
Bilal Hussain;
Veronica Toccafondo;
Marco Chiesa;
Claudio Porzi;
Antonella Bogoni;
Paolo Ghelfi
Show Abstract
We report the design and implementation of a beam-forming network based on packaged integrated photonic circuits. Each of the four PICs emulating a phased-array antenna is optically fed by the 13GHz signal, and is able to adjust the phase exceeding 360° with a precision <1°. Experiments demonstrate an ultrafast antenna reconfiguration in less than 5ns
Modular and smooth introduction of photonics in high-throughput communication satellites – perspective of project BEACON
Author(s):
Vanessa C. Duarte;
João G. Prata;
Rogério N. Nogueira;
Georg Winzer;
Lars Zimmermann;
Rob Walker;
Stephen Clements;
Marta Filipowicz;
Marek Napierala;
Tomasz Nasilowski;
Jonathan Crabb;
Leontios Stampoulidis;
Javad Anzalchi;
Miguel V. Drummond
Show Abstract
In this paper we present a 4-channel silicon photonic true-time delay (TTD) beamformer in which the phase of each channel is automatically adjusted in real-time. Beamforming was demonstrated with a 1 Gb/s QPSK signal carried at 28 GHz. The demonstration comprised the following custom made devices: two arrays of GaAs Mach-Zehnder modulators (MZMs), a radiation-hardened 7-core erbium-doped fiber amplifier (MC-EDFA) for power boosting, and a silicon photonic integrated circuit (PIC) containing a 4 × 1 TTD optical beamformer network (OBFN). Having provided a successful proof-of-concept demonstration, the dimensioning of an end-to-end photonic-aided payload receiver is here studied. It comprises the proposed OBFN fed by 100 antenna elements (AEs) in a multibeam scenario, also providing an estimation of the system’s power consumption.
Demonstration of strain independent temperature measurements using optical PM-FBG sensors for ground testing of satellite panels
Author(s):
Selwan K. Ibrahim;
Raymond McCue;
John A. O'Dowd;
Martin Farnan;
Devrez M. Karabacak
Show Abstract
Photonically wired spacecraft panels have been demonstrated within a recent ESA ARTES project by integrating mechanically packaged fiber Bragg grating (FBG) based optical temperature sensors into a honeycomb satellite test panel. Replacing electrical sensors with optical fiber sensors for testing satellites should have the advantage of reducing the harness mass and AIT. Fiber optic sensing also comes with clear benefits including immunity to electromagnetic interference and the capability of supporting arrays of sensors on a single fiber. However, standard FBG based temperature sensors are sensitive to both strain and temperature and in order to measure both strain and temperature simultaneously, two FBG sensors are required. An alternative solution using birefringent FBGs inscribed in Polarization Maintaining (PM) fiber (PM-FBG) in combination with high precision optical interrogators offers the same capabilities of standard FBG based optical sensors with high accuracy measurements, and can simultaneously measure both strain and temperature using only one sensor. PM-FBG sensors can also be multiplexed on a single fiber and therefore offer a simplified installation option by mounting them on the surface of the structure without the requirement for complex transducer packaging designs. With the support from an ESA GSTP project, we have developed an optical interrogator that measures PM-FBGs with high accuracy. The aim of the project is to demonstrate an optical strain independent temperature measurement system using PM-FBGs installed on a satellite test panel in atmospheric pressure and thermal vacuum environments with an operating temperature range from -20°C to + 80°C.
Mitigating the effect of space small debris on COPV in space with fiber sensors monitoring and self‐repairing materials
Author(s):
Emile Haddad;
Yi Zhao;
Mert Celikin;
Matteo Basti;
Kamel Tagziria;
Elad Wallach;
Christopher Semprimoschnig;
Ugo Lafont;
Iain McKenzie
Show Abstract
Small space debris are a high risk for the walls of Composite Overwrapped Pressure Vessels (COPV), by making small holes and causing the fuel leak. Commonly the self-healing materials are used to keep the mechanical structure strength, here the hermeticity of the repaired portion is a stringent requirement, to prevent any potential fuel leak from the cryogenic tank in vacuum. The efficiency is compared for protective walls composed of a combination of various layers, using strong materials (Kevlar, Nextel) and self-healing commercial materials developed as bulletproof, e.g. the Ethylene-co-Meth Acrylic Acid (EMAA) and Reverlink
TM.
The small debris impact dynamic was detected and monitored with Fiber Bragg Gratings (FBG) sensors at very fast acquisition frequencies, up to 0.5 GHz (2 ns), measuring the variation of the total reflected signal by the FBG. The acquisition system is based on commercially available products. To measure the total wavelength spectrum, the fastest available spectrometer can go up to 2 MHz acquisition (Micron-Optics), which is insufficient to detect the hypervelocity impact. The impact pressure evolution of the FBG, placed in the middle layer, was compared with commonly used strain gauges placed a few layers further or on the back of the last layer. The measured impact time delay and relative intensity were compatible between the two sensing methods.
Some samples were characterized in details using the X-ray Computed Tomography at ESTEC, they permitted us to confirm the results by observing the details of the healing and follow the impact trajectory visually.
In-orbit demonstration of fiber optic sensors based on Bragg gratings
Author(s):
Raquel López Heredero;
Malte Frövel;
Hugo Laguna;
Tomás Belenguer
Show Abstract
FIBOS (FIber Bragg gratings for Optical Sensing) is one payload used to monitor temperature and strain during a nanosatellite mission. Description of the payload and in-orbit results are presented.
Fiber Bragg Grating (FBG) sensors offer attractive and robust solutions for temperature and pressure monitoring in a spacecraft. Moreover, they can be embedded in composite structures or attached on their surface for structural health monitoring during the entire life cycle of a satellite, from integration and qualification tests, to final operation.
FIBOS contains two FBGs to measure temperature and strain during one space mission called OPTOS. The mission, developed by INTA (Instituto Nacional de Técnica Aeroespacial), was a low-cost nanosatellite based on a triple configuration (3U) of the popular Cubesat standard. OPTOS was launched in November 2013 and was operative during two years. Its main goal was to validate and demonstrate the suitability of novel technologies for space applications inside a miniaturized area with big restrictions in terms of mass and power consumption.
This work describes the payload components. FIBOS contains commercial off-the-shelf (COTS) parts like a monolithic tunable laser and a conventional InGaAs pigtailed photodiode. The optical sensor head includes two FBGs mounted onto a steel mechanical structure to monitor temperature and strain. Results of the mission are presented. Measurements performed during the operation in-orbit show good agreement with calibration data performed on earth inside a thermalvacuum chamber (TVC). This paper shows a demonstration of a fiber optic sensor based on FBGs in space environment.
Optical fiber interconnect: standards, procurement, lesson learned and future applications
Author(s):
Frédéric Taugwalder
Show Abstract
The ESCC has published new optical fiber connectors standards destined to simplify procurement of such components. A summary presentation is given, but more importantly, how to use them, the lesson learned from Diamond’s perspective is presented. The latter cover the fiber lot management, the radiation and a few other parameters necessary for projects.
Three main application categories are presented: A) Generic-Sensing, B) Satellite external communication, C) Satellite internal communication. Their products range and covered solution is presented, with potential new development proposed
A Ka-band single string photonic payload flight demonstrator for broadband high throughput satellite systems and an in orbit demonstrator of optical RF distribution on board satellites
Author(s):
Miguel A. Piqueras;
Javier Martí;
Silvia Delgado;
Rob Singh;
Robert Parish;
Ghislain Turgeon;
Agustin Zornoza
Show Abstract
This paper provides a summary of two on orbit demonstrators (IOD) for photonics payload technology hosted in two satellites respectively. A Ka-band Flight Demonstration Photonic Payload aimed for payload solutions for High Throughput Satellites (HTS) Systems was hosted in a GEO Communication satellite. An Optical RF Distribution flight demonstration was hosted in a second GEO satellite. This paper provides the design, parameter allocations and testing of these payloads. It describes the system and payload design solution overviews, identifies critical payload hardware, and summarizes key unit and payload performances for the Ka Band Flight demonstration payload and for the Optical distribution of RF signals. Both in-flight demonstrations are now flying as hosted payloads in two different GEO communications satellite recently launched.
50GHz gallium arsenide electro-optic modulators for spaceborne telecommunications
Author(s):
Robert Walker;
Nigel Cameron;
Yi Zhou;
Chris Main;
Gary Hoy;
Stephen Clements
Show Abstract
Travelling-wave electro-optic modulators designed for V-band space applications using gallium arsenide guided-wave technology are presented. The designs feature a low-loss folded optical configuration giving straight-line RF access at one end of the chip, with all optical I/O via the opposite end. This configuration enables the close-packed monolithic modulator arrays needed for phased-array applications, contributes to high modulation bandwidths with low ripple by eliminating directional change in the RF feed arrangements and facilitates compact packaging. While only 1550nm designs are reported here, the AlGaAs material system is versatile, permitting modulators to be realized for a wide range of optical wavelengths, with particular advantage in drive-power at shorter wavelengths. Both single MZ and monolithic dualparallel (IQ) modulators have been assessed up to 70GHz; bandwidths around 50GHz are achieved with low-frequency Vπ of 4.6V. Typically, the folded devices are half the length of conventional format modulators and can accommodate 4 device arrays in the same width package.
Evaluation of optical switches for Space applications
Author(s):
David Poudereux;
Juan Barbero;
José Manuel G. Tijero;
Ignacio Esquivias;
Iain Mackencie
Show Abstract
We have evaluated the performance for space applications of commercial off-the-shelf fiber coupled optical switches with no-moving parts, based on different technologies. The technical requirements of several space applications of optical switches were defined. After the technology selection, a tradeoff was performed to select the final optical switches to be tested, which are based on three technologies (Magneto-Optic MO, Bulk Electro-Optic B-EO, and Waveguide Electro-Optic W-EO) and fabricated by four different manufacturers. Other potential technologies (acoustooptic, liquid crystal, thermo-optic, micro/nano photonic waveguides) were not selected due to the lack of commercial products. A test campaign was carried out, consisting of thermal vacuum cycles, mechanical tests (vibration and shocks) and radiation tests (gamma radiation). The main performance parameters were the insertion loss, crosstalk, and switching speed. After the final electro-optical characterization, a destructive physical analysis was made to some optical switches. The results of the tests indicated that B-EO and MO technologies are excellent candidates for the analyzed space applications. They respond very well under typical space conditions as radiation, vibration, shocks and thermal vacuum; B-EO technology presents lower switching time but its crosstalk is worse. WG-EO technology is very fast, but a mechanical failure in one device was observed, the insertion losses are very high and the crosstalk is very low.
A pipeline to improve compressed image quality
Author(s):
Jean-Marc Delvit;
Carole Thiebaut;
Christophe Latry;
Gwendoline Blanchet;
Roberto Camarero
Show Abstract
This paper presents a new image restoration pipeline performing especially well on noisy and compressed images. Most images are corrupted by noise. The signal to noise ratio (SNR) level increases with the pixel intensity value, which makes the denoising process especially challenging in dark areas of the images. Moreover, these areas are more likely to be highly compressed since they have low signal variations.
In this paper, we take into account compression by introducing a pre-processing step restituting the instrument noise. Then we propose a denoising and deconvolution step optimally parametrized since the instrument response (noise and Modulation Transfer Function) is known. We achieve better restoration than classical algorithms on satellite imagery. This improvement in image quality is shown on two kinds of application: pansharpening and 3D restitution.
Stratospheric balloons: low-cost platforms for science and technology development
Author(s):
F. Friedl-Vallon;
K. Dannenberg;
P. Raizonville;
A. Vargas
Show Abstract
Stratospheric balloons are useful platforms for various research and technology needs. In particular, they can be used for proof of concept demonstrations in preparation of new space and Earth observation missions. A typical balloon flight duration varies from a few hours to several weeks, depending on the balloon type, the choice of season, launch site and flight trajectory. Payloads can be flown at altitudes of 15-40 km. Compared to satellites, stratospheric balloons can be operated at relatively low cost and with shorter lead times from the experiment idea to the flight.
Recently, a new balloon infrastructure project called HEMERA has been selected by the European Commission within its programme Horizon 2020. One of the objectives of HEMERA is to enlarge the user community within research and technology related to stratospheric balloons and to coordinate activities within the field. The project is coordinated by the French space agency CNES and involves 13 partners from various European entities as well as the Canadian Space Agency, CSA. The project was kicked-off in late January 2018 and will be executed during 2018-2021.
Six balloon flights with a target payload mass of 150 kg are foreseen within HEMERA offering free of charge balloon flights to users and scientists from various science fields and/or for technology tests. In addition, several sounding balloon flights are foreseen for smaller payloads of up to 3 kg. The launch sites will be Esrange in Sweden, Timmins in Canada, and Aire sur l 'Adour in France. Two Calls for Proposals are planned in the HEMERA project. The selected experiments will fly on balloons during 2019-2021
General design of space optical remote sensing camera based on high-precision surveying and mapping requirements
Author(s):
Weijun Cai;
Xiaohong Zhang;
Fuqiang Li;
Jun Zheng;
Shitao Ding
Show Abstract
Space mapping satellites play an increasingly important role in Space mapping satellites play an increasingly important role in mapping and mapping. The positioning accuracy of mapping satellites is the core and key index for evaluating the performance of Surveying and mapping. At present, it has developed to the precision of the meter level. Therefore, in the design process of Surveying and mapping camera, it is not only necessary to ensure that the image has good MTF, signal to noise ratio, dynamic range and other basic radiation characteristics, but also need to focus on the high precision calibration of the interior orientation elements of optical system distortion, optical axis, focal distance and other questions of orbit stability.
In 2012 and 2016, China successfully launched ZY-3 (01/02) satellites, with a three-line-arrays camera and a multispectral camera. It is mainly used for the production of basic geographic information products of 1:50000 scale, and modification and updating of 1:25000 and larger scale topographic maps in China. The satellites have achieved good application results. Based on these experiences, driven by higher precision surveying and mapping requirements, as the main development and research organization of the Chinese space optical remote sensing camera, BISME has carried out a serial of research in the overall design of the space optical surveying camera. This paper gives some own views about the research for discussion and exchange.
Testing NISP instrument on ground
Author(s):
Anne Costille;
M. Carle;
E. Prieto;
M. Pons;
C. Fabron;
M. I. Andersen;
A. N. Sorensen;
N. C. Jensen;
S. M. Pedersen;
T. Maciaszek
Show Abstract
The Laboratoire d’Astrophysique de Marseille (LAM) is deeply involved in the development and the test of the NISP (Near Infrared Spectro-Photometer) instrument for the ESA EUCLID mission that will be launched in 2020. The goal of the mission is to understand the nature of the dark energy responsible for the accelerating expansion of the Universe. NISP is one of its two instruments operating in the near-IR spectral region (0.9-2μm) to map the geometry of the dark Universe. The integration of the NISP flight model (FM) has been started at LAM to allow its delivery in 2019 to the payload after vibration test and two thermal vacuum test campaigns to demonstrate the performance of the instrument. The thermal vacuum test will take place in ERIOS chamber, a 90m3 chamber developed by LAM to test optical instruments at cryogenics temperature and high vacuum. In addition to the chamber, a full and specialised set of ground support equipment called the Verification Ground System (VGS) is developed to fill the goal of the NISP test campaign. The test campaign combines functional tests of the detectors and wheels, performance tests of the instrument, calibration procedure validation and observations scenario test, all done at LAM. One of the main objectives of the test campaign is the measurement of NISP focus position with respect to the EUCLID object plane. The VGS is made of i) a telescope simulator to simulate the EUCLID telescope for optical performance tests, ii) a thermal environment to simulate the Euclid PLM thermal interfaces, iii) the NISP Electrical GSE (EGSE) to control the instrument during the test and iv) a Metrology Verification System (MVS) to measure the positions of NISP and the telescope simulator during the test. We present the set of GSE developed for NISP and their performance already validated during two blank tests: thermal blank test and metrology blank test. In addition, a blank test with all the VGS parts (thermal, optical, metrology) is scheduled in the coming months to validate the overall performance of this GSE including the telescope simulator. The goal is to measure with a high precision the focus distance of the telescope simulator at cold and the stability of the focus in time, and to demonstrate the functionality of the telescope simulator for NISP test campaign needs. Finally, we describe the thermal vacuum test configuration for the “end to end” test on the NISP flight model foreseen by beginning of 2019.
OPSys: optical payload systems facility for space instrumentation integration and calibration
Author(s):
Gerardo Capobianco;
Silvano Fineschi;
Giuseppe Massone;
Federico Landini;
Marta Casti;
Alessandro Bellomo;
Maurizio Deffacis;
Marco Romoli;
Ester Antonucci;
Vincenzo Andretta;
Giampiero Naletto;
Gianalfredo Nicolini;
Daniele Spadaro
Show Abstract
The Optical Payload System (OPSys) is an INAF (italian National Institute for Astrophysics) facility hosted by Aerospace Logistics Technology Engineering Company (ALTEC SpA) in Turin, Italy. The facility is composed by three clean rooms having different cleanliness levels, a thermo-vacuum chamber (SPOCC, Space Optics calibration Chamber) with a motorized optical bench and several light sources covering the range from the extreme ultraviolet to the red light wavelengths. The SPOCC has been designed having in mind the very stringent requirements of the calibration of solar coronagraphs and the suppression of the stray-light. The facility and the optical performances will be described here. The calibration campaign performed on Metis space coronagraph will be reported as a case study.
METimage instrument development status
Author(s):
Oswald Wallner;
Klaus Ergenzinger;
Frank Schmülling
Show Abstract
METimage is a cross-purpose, medium resolution, multi-spectral optical imaging radiometer for meteorological applications onboard the MetOp-SG satellites. It is capable of measuring thermal radiance emitted by the Earth and solar backscattered radiation in 20 spectral bands from 443 to 13.345 nm. We provide an overview over the instrument design and present the instrument development status.
Optical harness (OHA) for future L-band radiometer
Author(s):
M. A. Piqueras;
T. Mengual;
J. Blasco;
M. Aamer;
O. Navasquillo;
J. I. Ramírez
Show Abstract
Soil Moisure and Ocean Salinity (SMOS) was the first ESA satellite relying on a complete optical harness, which was initially selected for the mechanical properties of optical fibre, what facilitated the deployment of the 3 arms of the instrument. In addition, other interesting advantages of the optical harness, as immunity to electromagnetic interference, high bandwidth, low losses and mass, etc., played an important role in the instrument performance.
In the frame of the the ESA ITI contract No 4000120740/17/NL/AI, based on the advantages of optical cables and the good results obtained in SMOS mission, DAS team along with Airbus DS is studying different optical harness configurations as an evolution towards a full optical harness system for a future SMOS Operational (SMOS-OPS) Lband radiometer. In particular, different Optical Harness (OHA) configurations have been studied in order to select the two most promising options.
The first configuration aims at solving some identified issues as well as at improving performance of SMOS thanks to lessons learnt from the in-orbit operation, but without attempting novel techniques of calibration or signal distribution.The second configuration explores the application of alternative techniques like the use of WDM or multi- RF over fibre. The main goals of this second configuration are the improvement of the electrical performance and the optimization of the optical harness in terms of layout, i.e, to reduce number of cables/fibres, size, weight, as well as power consumption.
Design and on-orbit calibration of the solar ultraviolet imager (SUVI) on the GOES-R series weather satellite
Author(s):
Gopal Vasudevan;
Lawrence Shing;
Dnyanesh Mathur;
Christopher Edwards;
Margaret Shaw;
Daniel Seaton;
Jonathan Darnel
Show Abstract
The GOES-R series is the latest in a long line of American geostationary weather satellites operated by NOAA (National Oceanic and Atmospheric Administration). The Solar Ultraviolet Imager (SUVI) is an instrument onboard Geostationary Operational Environmental Satellites, GOES-R series, part of NOAA's (National Oceanic and Atmospheric Administration) space weather monitoring fleet. GOES-16 SUVI is in operation and the GOES-17 SUVI has completed initial calibrations.
SUVI is a generalized Cassegrain telescope with a large field of view that employs multilayer coatings optimized to operate in six extreme ultraviolet (EUV) narrow bandpasses centered at 9.4, 13.1, 17.1, 19.5, 28.4 and 30.4 nm. The SUVI EUV line set provides the best comprehensive feature and dynamics information for revealing and correlating both the low coronal signatures of coronal mass ejections (CME) triggers (for example, flares) and the high coronal signatures of the actual CME. SUVI acquires full disk images in EUV band pass every few minutes and telemeters the data to the ground for digital processing. These data will enable NOAA to monitor solar activity and to issue accurate near real-time alerts when space weather may possibly affect the performance and reliability of space-borne and ground-based technological systems and human endeavors.
This paper describes key design drivers in the development of SUVI, methods used in the autonomous on-orbit calibration of the instrument, and the automated monitoring of the health and safety of the instrument during operations.
Radiation tests on the COTS image sensor from CMOSIS
Author(s):
Pawel Adamiec;
Juan Barbero;
Alejandro Lopez Moya;
Enrique Cordero
Show Abstract
12 Mpix color commercial-of-the-shelf (COTS) image sensor from CMOSIS was tested with proton radiation. The target mission required an irradiation with protons of energy of 50 MeV and fluences up to 1·1012 p/cm2. Several intermediate steps were introduced to check the behavior of the image sensor. A low-cost test camera was developed to control the image sensors, acquire the images, and monitor the currents and voltages during the tests. Each color was characterized separately according to the EMVA 1288 standard. Such treatment allowed also analysis of the bayer filter deposited on the image sensor surface. Post-radiation characterization revealed that a significant deterioration in the parameter performance was found independently of the pixel color. The most affected parameters were dark current and dark signal nonuniformities (DSNU) which have increased from about one to two orders of magnitude.
SIMBIO-SYS STC ready for the first light: the radiometric calibration
Author(s):
A. Slemer;
E. Simioni;
V. Da Deppo;
C. Re;
M. Dami;
D. Borrelli;
I. Ficai Veltroni;
G. Aroldi;
L. Tommasi;
M. T. Capria;
G. Naletto;
R. Mugnolo;
M. Amoroso;
G. Cremonese
Show Abstract
The Stereo Channel (STC) is a double wide-angle camera developed to be one of the channels of the SIMBIO-SYS instrument onboard of the ESA BepiColombo mission to Mercury. STC main goal is to map in 3D the whole Mercury surface.
The geometric and radiometric responses of the STC Proto Flight model have been characterized on-ground during the calibration campaign. The derived responses will be used to calibrate the STC images that will be acquired in flight. The aim is to derive the functions that link the detected signal in digital number to the radiance of the target surface in physical units.
The result of the radiometric calibration consists in the determination of well-defined quantities: i) the dark current as a function of the integration time and of the detector temperature, nominally fixed at 268 K; ii) the Read Out Noise, which is associated with the noise signal of the read-out electronic; iii) the Fixed Pattern Noise, which is generated by the different response of each pixel; iv) once these quantities are known, the photon response and the Photo Response Non-uniformity, which represent the variation of the photon-responsivity of a pixel in an array, can be derived.
The final result of the radiometric calibration is the relation between the radiance of an accurately known and uniform source, and the digital numbers measured by the detector.
Dynamic MTF estimate of the optical imager onboard Alsat-1B satellite
Author(s):
Chahira Serief;
Youcef Ghelamallah
Show Abstract
Unwanted movements during image recording usually cause problems for optical imaging systems onboard Earth Observation satellites. The major effect of these movements is the degradation of image quality by smearing and distortion. The aim of this paper is to provide estimates of the blur-caused MTF of an isolated CCD detector element as a result of linear motion to evaluate the impact of such blur, that may be experienced operationally, on the whole system MTF of the Alsat-1B imager. The estimates are made on ground prior to launch and include effects caused by linear motion of the spacecraft relative to the earth and exclude effects of motion caused by mechanical vibration or platform drift. Those estimates are of great importance as part of system level analysis which can help restoring the degraded image.
Study of the coherent perturbation of a Michelson interferometer due to the return from a scattering surface
Author(s):
Vitalii Khodnevych;
Sibilla Di Pace;
Jean-Yves Vinet;
Nicoleta Dinu-Jaeger;
Michel Lintz
Show Abstract
We describe a setup based on Michelson interferometry for coherent measurements of the backscattered light from a low roughness optical surface under test. Special data processing was developed for the extraction of the useful signal from the various stray contributions to the coherent signal. We achieve coherent detection of light scattered by a mirror down to -130 dB in optical power. We characterize the dependence of the backscattered light with spot position and incidence angle. Results of cross-polarization scattering coherent measurements and preliminary results of dust deposition experiment are presented here. This work represents the first step in the experimental evaluation of the coherent perturbation induced by the scattered light in the space gravitational wave detector of the LISA mission.
Advent of the IBIS as the digital sunsensor for the future
Author(s):
J. Leijtens;
D. Broekmans;
S. Schmidt;
G. van der Horn;
R. Visee
Show Abstract
For many years there have been attempts to eliminate the earth albedo sensitivity for Sunsensors. This is best done through development of a true digital Sunsensor.
The best known digital Sunsensor was designed (and patented) by Adcole back in the 1970's only to be followed by the Leonardo smart digital Sunsensor and a small digital Sunsensor developed by Sinclair interplanetary some 30 years later. The first two sensors are relatively large and expensive, whereas the later is small and affordable but lacks the required radiation tolerance and quality level required for longer duration ESA missions. Although TNO attempted to develop a small but highly reliable Sunsensor between 2004 and 2010, this development did not lead further than the prototype called mini-DSS.
From this TNO research and developments it became apparent that the detector technology and detection principle used are key to delivering the desired properties: high reliability, low cost, small form factor and low power consumption.
While Leonardo stopped the development of a small digital Sunsensor in 2017, Lens R&D is now developing such a device in frame of an ESA Artes 5.1 contract signed in April 2018.
Based on insights developed during the TNO mini/micro-DSS program and a new operating principle, the Intensity Based Images Sensing (IBIS) principle is expected to lead to a producible sensor that is low power, highly reliable and cost effective.
The dedicated imager (dubbed IPS) required for the demonstrator to be built within the framework will be designed by SystematIC Design and is expected to show a very low power consumption and low operation voltage. These properties are important in order to allow for further design optimizations related to potential autonomous powering or power over data applications.
The presentation will focus on the status of the Artes program design considerations for the IBIS sensor and the optical design of the sensor, which is core to providing a highly reliable but cost-effective sensor.
MINISTAR: a miniaturized device for the test of star trackers
Author(s):
Vanni Nardino;
Donatella Guzzi;
Matteo Burresi;
Massimo Cecchi;
Tommaso Cecchi;
Francesco Corti;
Marco Corti;
Enrico Franci;
Gabriele Guidotti;
Ivan Pippi;
Lorenzo Salvadori;
Chiara Spagnesi;
Valentina Raimondi
Show Abstract
Star trackers are electro-optical devices that are used to determine the attitude of satellite platforms. The test of star trackers is typically carried out by means of Optical Ground Support Equipment (OGSE). In this paper we present a new prototype of OGSE, the MINISTAR, recently developed by a consortium of Italian enterprises and the Applied Physics Institute of the National Research Council. The MINISTAR is a miniaturized electro-optical device able to generate synthetic images of dynamic star fields for the simultaneous test of up to three star trackers. Their performance can be evaluated in terms of its optics, electronics and on-board attitude software. The MINISTAR is able to perform a dynamic simulation of the apparent motion of the observed scene in order to test the star tracker in a realistic working scenario. It can be placed directly on the star tracker under test and, thanks to its reduced dimensions and weight, the test and validation phase can be performed while the star tracker is assembled on the satellite platform. The MINISTAR is also able to simulate the presence of large objects, such as the Sun, the Earth and the Moon, custom objects and disturbances like cosmic rays and stray light effects. The prototype has been built paying special attention to the employed materials and technology in order to minimize the weight and to ensure its compatibility with most star tracker models available on the market.
Stray light solution for GHGSAT nanosatellite
Author(s):
Vincent Latendresse;
Dina Katsir;
Keren Shabtai;
Jason McKeever;
Victor Isbrucker;
Jonathan Lavoie;
Roman V. Kruzelecky;
Wes Jamroz
Show Abstract
GHGSat is world’s first nanosatellite dedicated for monitoring greenhouse gas (GHG) and air quality gas (AQG) emissions from any industrial site in the world. The satellite was designed and constructed by MPB Communications to monitor carbon dioxide (CO2) and methane (CH4) from a low earth orbit (about 500 km). To reach the designated resolution of less than 50 meters and high precision of greenhouse gases monitoring, the nanosatellite has large aperture in order to collect enough optical signal. The aperture of about 10cm causes significant stray light issues with limited solution options without adding too much weight to the light weight satellite. As the stray light was the main concern in this project, many precautions was taken. As a solution for blocking unwanted light, baffle with many vanes was used. However, having the vanes is not optimal solution without high absorbing coating applied on it. The coating requirements was low reflectance, no outgassing in space environment and long life stability, being a satellite inaccessible for maintenance. The chosen coating for stray light elimination was Acktar Vacuum BlackTM. Hemispherical reflectance and BRDF data was examined before making the choice. The satellite was launched in June 2016 and the images was analyzed to ensure the aimed resolution and precision of the optical system. After almost two years of activity, no visible changes was discovered in image quality nor stray light issues detected.
An absolute optical frequency reference for space
Author(s):
Thilo Schuldt;
Markus Oswald;
Martin Gohlke;
Klaus Döringshoff;
Evgeny Kovalchuk;
Achim Peters;
Claus Braxmaier
Show Abstract
A variety of future space missions rely on the availability of high-performance optical frequency references with applications in fundamental physics, geoscience, Earth observation and global satellite navigation systems (GNSS). Examples are the gravitational wave detector LISA (Laser Interferometer Space Antenna), the Earth gravity mission NGGM (Next Generation Gravity Mission) and missions, dedicated to tests of Special Relativity, e.g. by performing a Kennedy-Thorndike experiment testing the boost dependence of the speed of light. In this context, we developed optical frequency references based on Doppler-free spectroscopy of molecular iodine where compactness and mechanical and thermal stability are main design criteria. We demonstrated a frequency instability of 6•10-15 at 1 s integration time and 3•10-15 for integration times between 100 s and 1.000 s. Furthermore, a very compact spectroscopy setup was realized for the sounding rocket mission JOKARUS which was successfully flown in May 2018. In a current activity, an integrated high-performance iodine-based frequency reference is developed which serves as a demonstrator for future GNSS using optical technologies.
End to end calibration of a radiometer at high irradiance levels
Author(s):
Steven van den Berg;
Omar El Gawhary;
Paul Dekker;
Marijn van Veghel;
Ramon Vink;
Steven Sablerolle;
Gianluca Casarosa
Show Abstract
In this contribution we present a method to calibrate a radiometer at high irradiance levels (18 kW/m2). The method has been developed in the frame of the ESA Technology Research Programme. The radiometer under test is used as a reference detector in solar simulators. In order to underpin that the irradiance level that is generated in the solar simulator is within the required levels of uncertainty, the performance of the reference radiometer has been validated. The concept of the calibration of the radiometer is that the radiometer cavity is exposed to a known optical flux, provided by a laser. Taking into account the area of the cavity aperture, which is measured independently with a coordinate measurement machine, the average irradiance level is determined. The reading of the radiometer is then compared to the applied irradiance level. For this calibration the challenge is not only to achieve SI traceability at high irradiance levels, but also to meet other requirements like not to exceed a pre-determined level of irradiance at any position of the radiometer cavity, to avoid potential damage. The measurement uncertainty for the calibration of the instrument is <1%. Results show that the irradiance provided by the radiometer agrees within the measurement uncertainty with the known applied irradiance over the tested calibration range (0.04 W/cm2 - 1.8 W/cm2).
Image-based wavefront correction for space telescopes
Author(s):
Orestis Kazasidis;
Sven Verpoort;
Ulrich Wittrock
Show Abstract
With a view to future large space telescopes, we investigate image-based wavefront correction with active optics. We use an image-sharpness metric as merit function to evaluate the image quality, and the Zernike modes as control variables. In severely aberrated systems, the Zernike modes are not orthogonal to each other with respect to this merit function. Using wavefront maps, the PSF, and the MTF, we discuss the physical causes for the non-orthogonality of the Zernike modes with respect to the merit function. We show that for combinations of Zernike modes with the same azimuthal order, a flatter wavefront in the central region of the aperture is more important than the RMS wavefront error across the full aperture for achieving a better merit function. The non-orthogonality of the Zernike modes with respect to the merit function should be taken into account when designing the algorithm for image-based wavefront correction, because it may slow down the process or lead to premature convergence.
Fiber optic gyroscope For 6-component planetary seismology
Author(s):
F. Guattari;
E. de Toldi;
R. F. Garcia;
D. Mimoun
Show Abstract
Planetary seismology is a key technique for imaging the internal structure of planetary objects. It targets some of the most fundamental science objectives, from the formation of planetary systems to the characterization of habitable worlds. However, standard methods suffer from various limitations inherent to planetary missions, first one being that a single station is much easier to settle than an array.
Taking benefit of the latest developments in so-called “rotational seismology”, it appears that a single instrument able to monitor both translations and rotations of planetary surfaces would be a game changer in planetary seismology. Indeed, in addition to perform both seismology and global rotational monitoring of the planetary object, the measurement of 6 Degrees of Freedom (DoF) brings a significantly increased scientific return compared to classical 3-DoF sensors.
Hence, to enter a new realm of planetary exploration with an innovative ground motion instrumentation concept relying on high precision sensors based on optical interferometry, a project named PIONEERS has been submitted (April 2018) and accepted (July 2018) by European Commission through its H2020 program.
Under the leadership of ISAE-SUPAERO, gathering IPGP, ETH-Z, Royal Observatory of Belgium, LMU and iXblue, the PIONEERS team aims to develop two innovative 6-Dof instruments for measuring ground deformation on planetary objects.
The first instrument is a prototype of very low noise 6-Dof sensor dedicated to the imaging of the internal structure of terrestrial planets. The second one is a high TRL CubeSat version of the same instrument concept for exploration of small bodies.
An optical distribution board for atom quantum experiments in space (a numerical analysis)
Author(s):
I. Drougkakis;
K. G. Mavrakis;
K. Poulios;
G. Vasilakis;
D. G. Papazoglou;
W. von Klitzing
Show Abstract
We present the theoretical analysis of a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling schemes on optical breadboards. This technique uses glass wedges and plates to correct misalignments in the position and angle of beams on the breadboard. It can be used in any application where stable and robust coupling of light from an input to an output fiber is required, such as laser distribution boards for cold atom experiments in space. We examine the optical performance in terms of coupling efficiency (CE) for a number of different OBST systems and compare the results. Coupling efficiencies above 95% and positional and angular resolution of smaller than 5 μm and 5 μrad can be achieved using this technology.
PROBA-3 formation-flying metrology: algorithms for the shadow position sensor system
Author(s):
M. Casti;
A. Bemporad;
S. Fineschi;
G. Capobianco;
D. Loreggia;
V. Noce;
F. Landini;
C. Thizy;
D. Galano;
R. Rougeot
Show Abstract
PROBA-3 ESA’s mission aims at demonstrating the possibility and the capacity to carry out a space mission in which two spacecrafts fly in formation and maintain a fixed configuration. In particular, these two satellites - the Coronagraph Spacecraft (CSC) and the Occulter Spacecraft (OSC) – will form a 150-meters externally occulted coronagraph for the purpose of observing the faint solar corona, close to the solar limb – i.e. 1.05 solar radii from the Sun’s center (R
Θ). The first satellite will host the ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire) coronagraph as primary payload. These features give to the PROBA-3 mission the characteristics of both, a technological and a scientific mission.
Several metrology systems have been implemented in order to keep the formation-flying configuration. Among them, the Shadow Position Sensors (SPSs) assembly. The SPSs are designed to verify the sun-pointing alignment between the Coronagraph pupil entrance centre and the umbra cone generated by the Occulter Disk. The accurate alignment between the spacecrafts is required for observations of the solar corona as much close to the limb as 1.05 R
Θ.The metrological system based on the SPSs is composed of two sets of four micro arrays of Silicon Photomultipliers (SiPMs) located on the coronagraph pupil plane and acquiring data related to the intensity of the penumbra illumination level to retrieve the spacecrafts relative position. We developed and tested a dedicated algorithm for retrieving the satellites position with respect to the Sun. Starting from the measurements of the penumbra profile in four different spots and applying a suitable logic, the algorithm evaluates the spacecraft tri-dimensional relative position. In particular, during the observational phase, when the two satellites will be at 150 meters of distance, the algorithm will compute the relative position around the ideal aligned position with an accuracy of 500μm within the lateral plane and 500 mm for the longitudinal measurement. This work describes the formation flying algorithm based on the SPS measurements. In particular, the implementation logic and the formulae are described together with the results of the algorithm testing.
High performance silver coating with PACA2M magnetron sputtering
Author(s):
Catherine Grèzes-Besset;
Nathalie Valette;
Grégory Chauveau;
Matthieu Castelnau;
Karine Mathieu;
Matthieu Tatat;
Frédéric Lemarquis
Show Abstract
The performances that are required today for optical components are increasingly demanding, both in terms of the spectral response and the conditions to which the components are subjected. So-called dense deposition techniques for thin film coating currently make it possible to respond in many cases to this ever-increasing requirement. Indeed, conventional evaporation techniques that can address a large number of applications such as metallic coatings, antireflection coatings, mirrors, are no longer sufficient and we currently rely on the dense deposition techniques such as, for instance, magnetron sputtering which allow implementing layers stable and low-ageing behavior. In this paper, we will review the recent achievements at CILAS by magnetron sputtering technique on high-performance silver coatings for space applications.
In our premises in Aubagne, CILAS has implemented a large dimension in-line magnetron sputtering coating machine with which such silver coatings are realized. This equipment with oversized dimensions involving a 6 meters by 3 meters vacuum chamber, 12 turbomolecular pumps and 7 planar magnetrons over 2.50m long will be presented in detail. In particular, the wide range of configurations will also be illustrated with complex coatings achievements with respect to the capability of the machine which is equipped with magnetrons, that may be powered in Radio Frequency, Mid Frequency, Direct Current or pulsed Direct Current modes.
For several years, CILAS has improved its coating processes to produce high quality silver coatings, taking into account spectral performances, environmental conditions and also coating uniformity over 2meter by 2 meter dimensions.
Further developments have been led by CILAS with the support of the French Space Agency as part of Research and Development activities to improve environmental performance; we present here characterization results on samples before and after environmental qualification (temperature, humidity, vacuum heat ...) and on components with dimensions up to 600mm. A multi-year test campaign including stress measurements and adhesion tests on samples and mirror demonstrator will also be presented.
Linearly variable filters fabricated by magnetron sputtering technology
Author(s):
Thomas Bégou;
Frédéric Lemarquis;
Antonin Moreau;
Fabien Lemarchand;
Holger Reus;
Detlef Arhilger;
Harro Hagedorn;
Julien Lumeau
Show Abstract
Variable filters, which central wavelength of the bandpass shifts along one dimension of the component, is a promising way to simplify and to miniaturize imaging spectrophotometer systems for spatial observation. In fact, by combining a dispersive element and a variable filter, it is possible to realize a spectral and a spatial filtering based on pushbroom technique. While there were numerous methods developed in order to produce variable filters, at this date, there is no simple, reliable and repeatable method. In this paper, we present a new method for the fabrication of variable filters based on plasma assisted reactive magnetron sputtering (PARMS).
Variable filters are obtained upon the variation of the thickness of some or all the layers deposited on the substrate. The layers are deposited using a Bühler HELIOS machine in order to benefit from the high stability of the deposition process. To insure a non-uniformity of the deposited layers, adapted masks are placed in front of the targets for the low and high refractive index materials. The uniformity of these layers is measured via a custom set-up allowing a local measurement of the transmission to perform a mapping of the transmission over the whole component aperture.
In this paper, we present the fabrication of layers and filters with variable thickness. Various types of thickness gradients are presented.
Towards qualification longevity of high power Space optics
Author(s):
A. Melninkaitis;
G. Batavičiute;
C. Heese;
M. Šciuka;
L. Smalakys
Show Abstract
Laser systems dedicated to space missions require durable and well-characterized optics, that could ensure long-term operation under high average output power. If any of optical elements in such system experiences light-induced fatigue, the performance of whole laser system suffers. Thus, any delayed failure of the optical element would also endanger the entire space mission as repairing optic in the orbit is rather complicated. Up to now, the ability to predict optic’s longevity required by space programs was difficult and expensive, because of limited experimental data and lack of validated prediction models and methods. In order to address this problem, Lidaris and ESA joined forces for a two years cooperation project ESPRESSO. The overall aim of the project is to carry out research and development work required for essential preparation of reliable longevity qualification procedure to evaluate high power laser optics with intended use in space applications. Main elements of chosen methodology for optics lifetime prediction is reported in this paper. The essence of the proposed method lies in online video detection, failure mode (damage mechanism) separation and subsequent search of appropriate extrapolation models and methods. Main experimental findings confirm the suitability of the suggested approach for prediction of laser-induced damage threshold (LIDT) from a limited set of data to the extrapolated higher number of incident laser pulses.
Analysis and control of light scattered by optical components for space applications
Author(s):
M. Zerrad;
M. Lequime;
C. Amra
Show Abstract
Space applications require more and more demanding optical functions. This evolution led to the development of new generation of optical components with extreme performances in terms of scattering level, roughness, localized defects, spectral evolution of performances, coherent backscattering…. In this context, optical components produced for space applications present an increasing complexity with extreme specifications. As a consequence, new problematics specific to this generation of components appeared and among these, the management of light scattered by these components remains a significant challenge.
For example, for complex optical coatings (typically with more than 100 interfaces), the scattering response of the component is not directly correlated to the substrate spectrum, as it is the case for simple coatings (less than 40 layers). For this reason, an accurate modelling of light scattered by complex optical coatings requires a global analysis taking into account different parameters from the design and manufacturing to the conditions of use of the component.
We will present in this paper the last developments performed by the Scattering Group of Institut Fresnel for the modelling and the metrology of light scattered by complex optical components for space applications.
A specific care will be given to recent studies performed on narrow band filters for earth observation and high performances mirrors. For each of these applications, the specific problematics and corresponding challenges will be presented and experimental and numerical results will be detailed. The agreement between metrology and modelling will be highlighted.
A steep bandpass interference filter with FWHM 11nm centered at 1254nm for studying Lyman Alpha signatures of highly redshifted galaxies
Author(s):
A. Hull;
U. Brauneck;
J. Gallego;
N. Cardiel;
C. Cabello;
R. Guzmán;
J. M. Rodríguez-Espinosa;
A. Herrero;
M. Mas-Hesse;
E. Salvador;
A. Manrique;
A. Marín-Franch
Show Abstract
The presented new 1% narrowband filter centered at 1254nm with a FWHM of 11nm required and achieved excellent maximum transmission and deep out of band blocking. Magnetron sputtering was used for the filter coating process. The filter was used in the fully cryogenic near-infrared camera CIRCE of the Gran Telescopio Canarias (GTC) Telescope. The goal of the project is to detect very distant galaxies at the dawn of the Universe. These remote and extremely faint galaxies are selected by their Ly-alpha emission. We report on the spectral and interferometric results of the filter, and provide the spectacular first deep image taken with the 10.4m GTC telescope.
Integrated atomic quantum technologies in demanding environments: development and qualification of miniaturized optical setups and integration technologies for UHV and space operation
Author(s):
M. Christ;
A. Kassner;
R. Smol;
A. Bawamia;
A. Peters;
M. Wurz;
E. Rasel;
A. Wicht;
M. Krutzik
Show Abstract
Employing compact quantum sensors in field or in space (e.g., small satellites) implies demanding requirements on components and integration technologies. Within our work on integrated sensors, we develop miniaturized, ultra-stable optical setups for optical cooling and trapping of cold atomic gases. Besides challenging demands on alignment precision, and thermo-mechanical durability, we specifically address ultra-high vacuum (UHV) compatibility of our integration technologies and optical components. A prototype design of an UHV-compatible, crossed beam optical dipole trap setup and its application within a cold atomic quantum sensor is described.
First qualification efforts on adhesive micro-integration technologies are presented. These tests are conducted in application-relevant geometries and material combinations common for micro-integrated optical setups. Adhesive aging will be investigated by thermal cycling or gamma radiation exposure. For vacuum compatibility testing, a versatile UHV testing system is currently being set up, enabling residual gas analysis and measurement of total gas rates down to 5•10
-10mbar l/s at a base pressure of 10
-11 mbar, exceeding the common ASTM E595 test.
StrayLux: an efficient tool for stray-light modelling in optical instruments
Author(s):
Flavio Mariani;
Jerome Caron;
Matteo Taccola;
Semen Grabarnik;
Jean-Loup Bezy
Show Abstract
Stray-light components are an unavoidable part of the signal detected by most optical instrument; they can originate from different sources and optical design solutions can help reducing some of them. Diffuse stray-light results from the same scene observed by the instrument, and can deteriorate the radiometric performances especially in the presence of highlycontrasted scenes, as it often occurs in earth observation applications. When strict radiometric requirements are applied, as in the case of more recent mission studies, an assessment of stray-light levels can be relevant already in the early phases of an instrument development, to compare the performances of different concepts. For this task commercial stray-light tools using Monte-Carlo simulations can be extremely time consuming.
Here we present the software StrayLux, a tool to calculate the diffuse stray-light component of optical instruments. This software uses a semi-analytical approach to approximate stray-light contribution of the optical components of an instrument, resulting in shorter calculation times than Monte-Carlo simulations. The tool is completely written in Python, is provided with a graphical interface, and can interact with Zemax to extract the relevant parameters of an optical design.
The latest version of the software is currently made available to ESA industrial partners as a possible benchmark tool for stray-light estimation, within the instrument pre-development activities for future missions.
Design and realization of multispectral bandpass filters for space applications
Author(s):
C. Goury;
U. Brauneck;
V. Naulin;
S. Bourquin;
A. Rola;
I. Toubhans;
P. Pranyies;
C. Henry;
A. Hull
Show Abstract
Spectral and radiometric requirements of optical filters for space applications are always more demanding. Multispectral bandpass filters require very steep edges, a high accuracy in the central wavelength position, a high average transmittance as well as a very good level of blocking outside of the bandpass region.
Realization of such filters implies to design the layer stacks in a way that reduces sensitivity to the production deviations and to be able to properly control the coating conditions in the machine.
In order to optimize the design, a pre-production error analysis can be performed, to assess the weight of each layer in the global filter properties and therefore modify the design until a good stability level is achieved. We discuss different insitu optical monitoring strategies and process conditions depending on the coating technology. The realization phase needs a precise control of the coating machine such as well-characterized deposited materials, stable deposition rates, a reliable layer thickness monitoring system in addition to a good coating uniformity over all the coating positions inside the machine.
We present design strategies and means of pre-production error analysis for typical multispectral bandpass specifications as well as transmittance curves.
Shock and vibration tests of space light-weighted corner cubes manufactured with adhesion process
Author(s):
N. Cocheteau;
C. du Jeu;
M. Voisin;
A. Maurel-Pantel;
F. Lebon;
S. Begoc
Show Abstract
The interferometer of the third generation meteorological satellite is composed by two corner cubes. The specifications, in terms of optical performances - wave front error (WFE) - and mechanical and thermal environments are very stringent compared to the actual knowledge. To answer to the mass, optical and mechanical specifications, a lightweighted hollow corner cube have been designed. An integration process based on enhanced molecular adhesion have been developed and tested in collaboration with CNES and LMA. This process required a fine polishing of the three mirrors of the corner cube before adhesion in order to obtain a very low flatness, roughness and angle precision. The mechanical resistance of the enhanced molecular adhesion process have been validated on three mockups submitted to shock and vibrations. The optical performances have been demonstrate on flight model corner cubes.
Straylight of curved gratings: an interlaboratory comparison
Author(s):
Monika Kroneberger;
Dana Tomuta;
Andreas Mezger
Show Abstract
The accurate simulation of stray light is essential for the verification of the contrast requirements in optical instruments. In a spectrometer, the scattering from reflective gratings is difficult to characterize while contributing significantly to the overall system stray light and reduction of the spectrometer contrast.
Curved gratings also introduce higher straylight and difficulties in the verification of their straylight compliance. Scatterometers have to be adapted to the grating curvature and thus loose some of their performance.
While measuring a curved sample, this becomes part of the optical system of the scatterometer. For the AlbatrossTT and the CASI the system considering the curved sample has to be adapted to refocus the beam onto the detector. Additional aberrations modify the near angle limit, i.e. the smallest angle where the measured BRDF is higher than the system signature. Theoretical analysis of the scatterometer becomes necessary because the signature of the system is no longer directly measureable.
In addition, 2D BRDF measurement is adequate for characterization of a high polished optical surface or black coatings but deems to be insufficient to characterize all features of the grating scatter function.
3D measurement is essential to verify compliancy in all angular directions.
Small errors in the measurement procedure or measurement setup can lead to different results. Also every scatterometer setup has its own design driven limitations effecting near angle limit and resolution. To create reasonable results those limitations have to be carefully considered.
We present a set of measurements in two different laboratories with different scatterometers.
New light absorbing material for grazing angles
Author(s):
A. Yevtushenko;
A. von Finck;
D. Katsir;
A. Duparré
Show Abstract
One of the largest challenges for optical systems is eliminating stray light generated by reflections off the walls and other optical elements of the device. Most black coatings are not sufficiently effective at grazing angles. Acktar’s black coatings exhibit particularly low residual reflectance and have been implemented in various instruments. The new proposed material exhibits particularly low hemispherical and specular reflectance – especially at grazing angles.
An optically athermalized lens covering a 200-degree temperature range
Author(s):
John R. Rogers
Show Abstract
There are several methods for athermalizing an optical system. Active athermalization requires that the focus of the system be actuated as a function of temperature. This adds complexity to the system and is often not desired for Space applications. Mechanical athermalization does not attempt to stabilize or otherwise influence the optical behavior over temperature, but relies on a mount structure that is engineered to keep the focal plane array (FPA) located at the position of best focus over temperature. Often such mounts involve dissimilar materials expanding in opposite directions to obtain the desired net expansion. Optical athermalization keeps the mount structure simple but uses a modified optical design to ensure that the position of best focus falls at the FPA location across the temperature range. To achieve this while still producing a sharp image, the lens materials must be chosen carefully.
In designing an athermalized lens, the mounting details of the elements must be taken into account carefully. A common approach for optimization is to assume that the elements are separated by spacers whose CTEs are known. Unfortunately, in most cases this is not how the optical system is actually assembled. More commonly, the individual lenses are either cemented to or otherwise preloaded against seats cut into the housing barrel. Furthermore, there are many ways in which the contact between the optical elements and the housing takes place, and this influences the location where each element is “pinned” to the housing, i.e., the position at which there is no relative motion between the element and the housing.
In this paper, we present the design of a lens optimized to be optically athermalized over a 200° C temperature range. The design includes the effects of the lens mounting details as well as the change in CTE of aluminum over temperature. We also explore the sensitivity of the design to the mounting details and the CTE.
Development of VUV multilayer coatings for SMILE-UVI instrument
Author(s):
Jérôme Loicq;
Karl Fleury-Frenette;
Pascal Blain;
Alexandra Mazzoli;
Benoit Hubert;
Emma Spanswick;
Greg Enno;
Eric Donovan
Show Abstract
The Ultraviolet Imager (UVI) instrument is a very challenging imager developed in the frame of the SMILE-ESA mission. The UV camera will consist of a single imaging system targeted at a portion of the Lyman-Birge-Hopfield (LBH) N2 wavelength band. The baseline design of the imager meets the requirements to record snapshots of auroral dynamics with sufficient spatial resolution to measure cusp processes (100 km) under fully sunlit conditions from the specified apogee of the spacecraft. To achieve this goal, the UVI instrument utilizes a combination of four on-axis mirrors with an intensified FUV CMOS based camera. The mirrors will be coated with spectral selective interferometric layers to provide most of the signal filtering.
The objective of these filters is to select the scientific waveband between 160 and 180 nm. The combined four mirrors have to give an out-of-band rejection ratio as high as possible to reject light from solar diffusion, dayglow and unwanted atomic lines in a range of 10-8 – 10-9. Different multilayer coatings are considered and optimized according to the π- multilayer equation for different H/L ratio and for different angles of incidence.
Our theoretical evaluation shows a least a modification of the reflectance spectrum as a function of the angle of incidence, so that the optical beams hitting the different mirrors can have different optical properties depending on the optical fields and the distribution of the rays on the pupil. In this paper the effect of fields and coating homogeneity on the spectral throughput of the UVI instrument will be assessed and described.
Full-SiC derotator optics for METimage: preliminary design and verification approach
Author(s):
E. Renotte;
C. Bastin;
F. Bernard;
A. Bernat;
JM. Boitrel;
M. Bougoin;
C. Flebus;
E. Gillain;
P. Gloesener;
A. Jago;
G. Laffitte;
F. Lemagne;
D. Logut;
F. Mallet;
A. Mazzoli;
F. Michel;
M. Pfaffe;
M. Pinel;
J. -M. Schumacher;
F. Wolfs
Show Abstract
METimage is an advanced multispectral radiometer for weather and climate forecasting developed by Airbus Defence & Space under the auspices of the German Space Administration (DLR) for the EUMETSAT Polar System –Second Generation (EPS-SG). The instrument is equipped with a continuously rotating scan mirror with a 1.7s period followed by a static telescope. The scan mirror permits an extended Earth view of 108° per revolution and regular views to on-board calibration sources. A derotator assembly, which is half-speed synchronised with the scanner, is inserted in the optical beam after the telescope to compensate the image rotation in the focal plane. The derotator optical arrangement is a fivemirror concept that minimises the polarisation sensitivity. The derotator design is constrained by optical performance, mass and compactness, which led to the selection of a full silicon carbide (SiC) concept. This paper describes the preliminary design and verification approach of the derotator optics.
Manufacturing and qualification of the QM mirror for the high-resolution spectrometer of the FLEX mission
Author(s):
Luigina Arcangeli;
Giovanni Bianucci;
Fabio Marioni;
Ruben Mazzoleni;
Massimiliano Rossi;
Marco Terraneo;
Fabio E. Zocchi;
Marco Meini;
Francesco Galeotti;
Riccardo Gabrieli;
Fabio Belli;
Matteo Taccola
Show Abstract
FLORIS (FLuorescence Imaging Spectrometer) is the single High-Resolution Spectrometer instrument of the FLEX (FLuorescence EXplorer) mission, currently under development by the European Space Agency as the eighth Earth Explorer Mission. The goal of the mission is the monitoring of the chlorophyll fluorescence of plants giving information about their photosynthetic activity.
Leonardo Avionics & Space System Division is the prime contractor for the FLORIS Instrument for which Media Lario is manufacturing the QM unit of the spherical mirror included in the High-Resolution Spectrometer (HRSPE), hereafter called HRM mirror.
The High-Resolution Mirror is a 250-mm diameter spherical mirror with a radius of curvature of approximately 440 mm. For the mirror substrate, Leonardo has selected the Aluminium alloy AlSi40, a special alloy with 40% Silicon content, coated with a hard polishing layer of Nickel Phosphorus (NiP), deposited by electroless chemical process. The Silicon content allows this special Aluminium alloy to have the same coefficient of thermal expansion (CTE) of the NiP layer, therefore preventing thermal deformations deriving from the bimetallic effect. The mirror structure is light-weighted to approximately 2.8 kg. The required wave-front error of the mirror is better than 0.5 fringes PV, while the surface microroughness has been specified at 0.5 nm RMS due to stringent straylight requirements of the FLORIS instrument.
Media Lario has been selected for the mirror development phase because of their experience in the design and manufacturing of AlSi/NiP mirrors demonstrated in the development of the Earth Observation optical payload for small satellites (called STREEGO), based on an AlSi40 TMA telescope. The manufacturing process includes precision diamond turning, optical figuring and super-polishing. The optical coating will be done by Leonardo at their thin-films facility of Carsoli, Italy. Since the recipe prescribes to pre-heat the mirror surface at 100° C, Media Lario will qualify the mirror substrate with -25/+110°C thermal cycles to ensure adequate thermal stability for the coating process.
Developments of practical CdZnTe immersed grating and machined germanium/indium phosphide GRISM for a high-performance spectrograph in SPACE
Author(s):
Takashi Sukegawa;
Yukinobu Okura
Show Abstract
Dispersing elements are the key device of the spectrometer. Spectrograph in SPACE has various limitations at size and weight. An immersed grating and GRISM, which is made of high-index material is effective in solution of those problems. First, an absolute efficiency of dispersing element is very important, because the throughput of spectrograph has big relation with the mirror size that is almost equal with a scale of a satellite. When an immersed grating or GRISM made of high-index material with high-throughput is manufacturing, there are many difficulties as the fact known well. Especially it is difficult to obtain the ideal grooved shape and a sufficiently small surface flatness. CANON has already succeeded in the development of a practical Germanium (Ge) and Indium phosphide (InP) immersion echelle grating. On the other hands, about CdZnTe immersed grating, it was only succeeded in processing of grooved shaping on the immersed prism. There was not a back-reflection coating on the grooved surface, which was indispensable in order to obtain a high- efficiency. In this development, a back-reflection coating on the grooved surface for CdZnTe immersed grating has succeeded. Two devices for an actual proof shows very good absolute maximum diffraction efficiency (>75%) and small polarization dependability (< 1%). Since the back-reflection coating is a gold base, it is possible to apply in 10-20μm which range of wavelength is main objective in use of CdZnTe. Moreover, a machined Germanium/Indium phosphide GRISM also has succeeded. This GRISM is a type of transmittance. The grooves on GRISM were machined with a diamond tool. Manufacturing some GRISMs with different resolution, the minimum grooved pitch is about 2.2 μm. These GRISMs have the efficiency and the surface flatness compared with a ZnSe GRISM known before. As the conclusions, these devices are useful to the space application, and becomes indispensable to a high-performance spectrograph.
