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- Front Matter: Volume 8442
- Plenary Session
- ExoPlanet/Coronagraphic Missions and Technology I
- ExoPlanet/Coronagraphic Missions and Technology II
- ExoPlanet/Coronagraphic Missions and Technology III
- ExoPlanet/Coronagraphic Missions and Technology IV
- SPICA
- Euclid/WFIRST
- Small Missions/Explorers I
- Small Missions/Explorers II
- ECHO
- Technology
- Astrometry/GAiA
- Exoplanet and Combined Missions
- Hubble Space Telescope SM4/Spitzer
- Large Space Optics
- Solar Missions
- JWST Overview
- JWST Optics/I&T I
- JWST Optics/I&T II
- JWST Instruments
- Poster Session: ECHO
- Poster Session: EUCLID
- Poster Session: Hubble and SPITZER
- Poster Session: JWST
- Poster Session: SPICA
- Poster Session: Missions/Concepts
- Poster Session: Solar System
- Poster Session: Technologies
Front Matter: Volume 8442
Front Matter: Volume 8442
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This PDF file contains the front matter associated with SPIE Proceedings Volume 8442, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
Plenary Session
The cosmic microwave background: observing directly the early universe
Paolo de Bernardis,
Silvia Masi
Show abstract
The Cosmic Microwave Background (CMB) is a relict of the early universe. Its perfect 2.725K blackbody
spectrum demonstrates that the universe underwent a hot, ionized early phase; its anisotropy (about 80 µK rms)
provides strong evidence for the presence of photon-matter oscillations in the primeval plasma, shaping the initial
phase of the formation of structures; its polarization state (about 3 µK rms), and in particular its rotational
component (less than 0.1 µK rms) might allow to study the inflation process in the very early universe, and the
physics of extremely high energies, impossible to reach with accelerators. The CMB is observed by means of
microwave and mm-wave telescopes, and its measurements drove the development of ultra-sensitive bolometric
detectors, sophisticated modulators, and advanced cryogenic and space technologies. Here we focus on the new
frontiers of CMB research: the precision measurements of its linear polarization state, at large and intermediate
angular scales, and the measurement of the inverse-Compton effect of CMB photons crossing clusters of Galaxies.
In this framework, we will describe the formidable experimental challenges faced by ground-based, near-space and
space experiments, using large arrays of detectors. We will show that sensitivity and mapping speed improvement
obtained with these arrays must be accompanied by a corresponding reduction of systematic effects (especially
for CMB polarimeters), and by improved knowledge of foreground emission, to fully exploit the huge scientific
potential of these missions.
ExoPlanet/Coronagraphic Missions and Technology I
Review of small-angle coronagraphic techniques in the wake of ground-based second-generation adaptive optics systems
Show abstract
Small-angle coronagraphy is technically and scientifically appealing because it enables the use of smaller telescopes,
allows covering wider wavelength ranges, and potentially increases the yield and completeness of circumstellar
environment – exoplanets and disks – detection and characterization campaigns. However, opening up
this new parameter space is challenging. Here we will review the four posts of high contrast imaging and their
intricate interactions at very small angles (within the first 4 resolution elements from the star). The four posts
are: choice of coronagraph, optimized wavefront control, observing strategy, and post-processing methods. After
detailing each of the four foundations, we will present the lessons learned from the 10+ years of operations of
zeroth and first-generation adaptive optics systems. We will then tentatively show how informative the current
integration of second-generation adaptive optics system is, and which lessons can already be drawn from this
fresh experience. Then, we will review the current state of the art, by presenting world record contrasts obtained
in the framework of technological demonstrations for space-based exoplanet imaging and characterization mission
concepts. Finally, we will conclude by emphasizing the importance of the cross-breeding between techniques
developed for both ground-based and space-based projects, which is relevant for future high contrast imaging
instruments and facilities in space or on the ground.
Coronagraph focal-plane phase masks based on photonic crystal technology: recent progress and observational strategy
Show abstract
Photonic crystal, an artificial periodic nanostructure of refractive indices, is one of the attractive technologies for
coronagraph focal-plane masks aiming at direct imaging and characterization of terrestrial extrasolar planets. We
manufactured the eight-octant phase mask (8OPM) and the vector vortex coronagraph (VVC) mask very precisely using
the photonic crystal technology. Fully achromatic phase-mask coronagraphs can be realized by applying appropriate
polarization filters to the masks. We carried out laboratory experiments of the polarization-filtered 8OPM coronagraph
using the High-Contrast Imaging Testbed (HCIT), a state-of-the-art coronagraph simulator at the Jet Propulsion
Laboratory (JPL). We report the experimental results of 10-8-level contrast across several wavelengths over 10%
bandwidth around 800nm. In addition, we present future prospects and observational strategy for the photonic-crystal
mask coronagraphs combined with differential imaging techniques to reach higher contrast. We proposed to apply the
polarization-differential imaging (PDI) technique to the VVC, in which we built a two-channel coronagraph using
polarizing beam splitters to avoid a loss of intensity due to the polarization filters. We also proposed to apply the
angular-differential imaging (ADI) technique to the 8OPM coronagraph. The 8OPM/ADI mode mitigates an intensity
loss due to a phase transition of the mask and provides a full field of view around central stars. We present results of
preliminary laboratory demonstrations of the PDI and ADI observational modes with the phase-mask coronagraphs.
Status of the assessment phase of the ESA M3 mission candidate EChO
Show abstract
EChO is an M-class mission candidate within the science program Cosmic Vision 2015-2025 of the European Space
Agency. It was selected in February 2011 to enter an assessment phase (phase 0/A). Following the internal Concurrent
Design Facility study conducted by ESA in June/July 2011, a call for instrument studies was released in September,
resulting in two consortia being selected to study the complete science instrument on board EChO throughout 2012.
Similarly, two parallel competitive industrial studies of the complete mission will end early 2013.
The instrument study focuses on the design and accommodation in the spacecraft of the scientific instrument, a
spectrometer divided into several channels covering the 0.55 to 11 micron (0.4 to 16 micron goal) wave band. It also
includes the design of the active cryogenic chain required to operate the instrument focal plane detectors.
The industrial study focuses on the complete system-level design, including the mission analysis and operations, the
spacecraft design (both service and payload modules) and also programmatic aspects such as risk mitigation, schedule
and cost analyses.
This paper describes the status of the EChO assessment study at the mid-term review (June/July 2012). It includes a short
introduction to the EChO mission, a brief update on recent work by the Science Study Team (SST) to refine the science
requirements, the description of the telescope trade-off and baseline selection, as well as the status of both instrument
consortia and industrial system-level studies.
The achromatic chessboard, a new concept of a phase shifter for nulling interferometry: IV. Advanced experimental measurements
Show abstract
Context. To characterize their atmospheres in order to find evidences of life, one has to detect directly
photons from the exoplanets to measure their spectra. One possible technique is dark fringe
interferometry that needs an achromatic π phase shift in one arm of the interferometer. We have
conceived a phase shifter made of two cellular mirrors, in which each cell position and phase shift is
specific, so that the behaviour of the nulling with respect to wavelength is flat within a broad range.
Aims. We want to validate experimentally two versions of this achromatic phase shifter: a transmissive
one in bulk optics and a reflective one using a segmented deformable mirror. What we present in this
paper are the last results obtained in the lab.
Methods. We built an optical bench in the visible that allows us to test the principle and characterize
the performances and the limits of this phase shifter.
Results. We tested several transmissive and one reflective phase shifter and obtained, for instance, an
attenuation of about 2.10-3 for a white source (from 430 to 830 nm) that proved the achromatic
behavior of the phase shifter. The preliminary performances and limitations are analyzed.
ExoPlanet/Coronagraphic Missions and Technology II
High contrast vacuum nuller testbed (VNT) contrast, performance, and null control
Show abstract
Herein we report on our Visible Nulling Coronagraph high-contrast result of 109 contrast averaged over a focal plane
region extending from 1 – 4 λ/D with the Vacuum Nuller Testbed (VNT) in a vibration isolated vacuum chamber. The
VNC is a hybrid interferometric/coronagraphic approach for exoplanet science. It operates with high Lyot stop
efficiency for filled, segmented and sparse or diluted-aperture telescopes, thereby spanning the range of potential future
NASA flight telescopes. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop the VNC
and its technologies, and has developed an incremental sequence of VNC testbeds to advance this approach and its
enabling technologies. These testbeds have enabled advancement of high-contrast, visible light, nulling interferometry to
unprecedented levels. The VNC is based on a modified Mach-Zehnder nulling interferometer, with a “W” configuration
to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters.
We give an overview of the VNT and discuss the high-contrast laboratory results, the optical configuration, critical
technologies and null sensing and control.
EXCEDE technology development I: first demonstrations of high contrast at 1.2 l/D for an Explorer space telescope mission
Show abstract
Coronagraph technology is advancing and promises to enable space telescopes capable of seeing debris disks as well as
seeing and spectrally characterizing exo-Earths. Recently, NASA's explorer program has selected the EXCEDE
(EXoplanetary Circumstellar Environments and Disk Explorer) mission concept for technology development. EXCEDE
is a 0.7m space telescope concept designed to achieve raw contrasts of 1e-6 at an inner working angle of 1.2 λ/D and 1e-
7 at 2 λ/D. In addition to doing fundamental science on debris disks, EXCEDE will also serve as a technological and
scientific precursor for an exo-Earth imaging mission. EXCEDE uses a Starlight Suppression System (SSS) based on the
Phase Induced Amplitude Apodization (PIAA) coronagraph to provide high throughput and high contrast close to the
diffraction limit, enabling aggressive performance on small telescopes. We report on the latest progress in developing
the SSS and present coronagraphic performance results from our air testbed at NASA Ames. Our results include a lab
demonstration of 1e-5 contrast at 1.2 λ/D, 1.3e-6 contrast at 1.4 λ/D and 2e-8 at 2 λ/D in monochromatic light. In
addition, we discuss tip-tilt instabilities, which are believed to be our main limiting factor at present, and ways of
characterizing them.
Technology demonstration of starshade manufacturing for NASA's Exoplanet mission program
Show abstract
It is likely that the coming decade will see the development of a large visible light telescope with enabling
technology for imaging exosolar Earthlike planets in the habitable zone of nearby stars. One such technology utilizes an external occulter, a satellite flying far from the telescope and employing a large screen, or
starshade, to suppress the incoming starlight suffciently for detecting and characterizing exoplanets. This
trades the added complexity of building the precisely shaped starshade and flying it in formation against
simplifications in the telescope since extremely precise wavefront control is no longer necessary. In this paper we present the results of our project to design, manufacture, and measure a prototype occulter petal as
part of NASA's first Technology Development for Exoplanet Missions program. We describe the mechanical design of the starshade and petal, the precision manufacturing tolerances, and the metrology approach.
We demonstrate that the prototype petal meets the requirements and is consistent with a full-size occulter
achieving better than 10-10 contrast.
Electric field reconstruction in the image plane of a high-contrast coronagraph using a set of pinholes around the Lyot plane
Show abstract
In a setup similar to the self coherent camera, we have added a set of pinholes in the diffraction ring of the Lyot plane in a high-contrast stellar Lyot coronagraph. We describe a novel complex electric field reconstruction from image plane intensity measurements consisting of light in the coronagraph's dark hole interfering with light from the pinholes. The image plane field is modified by letting light through one pinhole at a time. In addition to estimation of the field at the science camera, this method allows for self-calibration of the probes by letting light through the pinholes in various permutations while blocking the main Lyot opening. We present results of estimation and calibration from the High Contrast Imaging Testbed along with a comparison to the pair-wise deformable mirror diversity based estimation technique. Tests are carried out in narrow-band light and over a composite 10% bandpass.
ExoPlanet/Coronagraphic Missions and Technology III
Broadband focal plane wavefront control of amplitude and phase aberrations
Show abstract
The Stroke Minimization algorithm developed at the Princeton High Contrast Imaging Laboratory has proven
symmetric dark hole generation using minimal stroke on two deformable mirrors (DM) in series. The windowed
approach to Stroke Minimization has proven symmetric dark holes over small bandwidths by using three
wavelengths to define the bandwidth of correction in the optimization problem. We address the relationship of
amplitude and phase aberrations with wavelength, how this changes with multiple DMs, and the implications for
simultaneously correcting both to achieve symmetric dark holes. Operating Stroke Minimization in the windowed
configuration requires multiple wavelength estimates. To save on exposures, a single estimate is extrapolated to
bounding wavelengths using the established relationship in wavelength to produce multiple estimates of the image
plane electric field. Here we demonstrate better performance by improving this extrapolation of the estimate to
other wavelengths. The accuracy of the functional relationship will ultimately bound the achievable bandwidth,
therefore as a metric these results are also compared to estimating each wavelength separately. In addition to
these algorithm improvements, we also discuss a laboratory upgrade and how it can better simulate broadband
starlight. We also discuss the possibility of leveraging two DMs in series to directly estimate the electric field
over a narrow bandwidth and the challenges associated with it.
A dark-hole correction test for the step-transmission filter based coronagraphic system
Show abstract
We present the initial test of the dark-hole correction for the high-contrast imaging coronagraph that is based on the step-transmission
filter. The dark hole is created by a 12x12 actuator deformable mirror (DM) that has been put in the
conjugate plane of the pupil image of the coronagraph. In this test, we use the stochastic parallel gradient descent
(SPGD) optimization algorithm to directly control the DM to provide an optimal phase to minimize the intensity in target
regions, where the dark hole is created and the contrast can be enhanced. For demonstration purpose, the test is carried
out in a single wavelength and should be improved in next step for broad-band high-contrast imaging. Finally, it is
shown in the test that an extra contrast ~50 times improvement has reached in the dark hole in the coronagraphic image
plane. Such a technique could be used for a future space-based high-contrast observation and is promising for the direct
imaging of an Earth-like exoplanet.
PICTURE: a sounding rocket experiment for direct imaging of an extrasolar planetary environment
Show abstract
The Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE 36.225 UG) was designed
to directly image the exozodiacal dust disk of ǫ Eridani (K2V, 3.22 pc) down to an inner radius of 1.5 AU.
PICTURE carried four key enabling technologies on board a NASA sounding rocket at 4:25 MDT on October
8th, 2011: a 0.5 m light-weight primary mirror (4.5 kg), a visible nulling coronagraph (VNC) (600-750 nm), a
32x32 element MEMS deformable mirror and a milliarcsecond-class fine pointing system.
Unfortunately, due to a telemetry failure, the PICTURE mission did not achieve scientific success. Nonetheless,
this flight validated the flight-worthiness of the lightweight primary and the VNC. The fine pointing system,
a key requirement for future planet-imaging missions, demonstrated 5.1 mas RMS in-flight pointing stability.
We describe the experiment, its subsystems and flight results. We outline the challenges we faced in developing
this complex payload and our technical approaches.
SPICA coronagraph instrument: characterization of atmospheres and physical parameters of giant planets by direct imaging and spectroscopy
Show abstract
We present the current status of the development of the SPICA Coronagraph Instrument (SCI). SPICA is a next-generation
3-meter class infrared telescope, which will be launched in 2022. SCI is high-contrast imaging, spectroscopic
instrument mainly for direct detection and spectroscopy of extra-solar planets in the near-to-mid infrared wavelengths to
characterize their atmospheres, physical parameters and evolutionary scenarios. SCI is now under the international
review process. In this paper, we present a science case of SCI. The main targets of SCI, not only for direct imaging but
also for spectroscopy, are young to matured giant planets. We will also show that some of known exoplanets by ground-based
direct detection are good targets for SCI, and a number of direct detection planets that are suitable for SCI will be
significantly increased in the next decade. Second, a general design of SCI and a key technology including a new high-throughput
binary mask coronagraph, will be presented. Furthermore, we will show that SCI is potentially capable of
achieving 10-6 contrast by a PSF subtraction method, even with a telescope pointing error. This contrast enhancement
will be important to characterize low-mass and cool planets.
Coronagraphic imaging of debris disks from a high altitude balloon platform
Show abstract
Debris disks around nearby stars are tracers of the planet formation process, and they are a key element of our understanding of the formation and evolution of extrasolar planetary systems. With multi-color images of a significant number of disks, we can probe important questions: can we learn about planetary system evolution; what materials are the disks made of; and can they reveal the presence of planets? Most disks are known to exist only through their infrared flux excesses as measured by the Spitzer Space Telescope, and through images measured by Herschel. The brightest, most extended disks have been imaged with HST, and a few, such as Fomalhaut, can be observed using ground-based telescopes. But the number of good images is still very small, and there are none of disks with densities as low as the disk associated with the asteroid belt and Edgeworth Kuiper belt in our own Solar System.
Direct imaging of disks is a major observational challenge, demanding high angular resolution and extremely high dynamic range close to the parent star. The ultimate experiment requires a space-based platform, but demonstrating much of the needed technology, mitigating the technical risks of a space-based coronagraph, and performing valuable measurements of circumstellar debris disks, can be done from a high-altitude balloon platform. In this paper we present a balloon-borne telescope concept based on the Zodiac II design that could undertake compelling studies of a sample of debris disks.
ExoZodi Mapper: a starshade probe mission
Show abstract
Direct detection and imaging of Exo-Earths is a prime candidate for the next Astrophysics flagship mission. Much effort
is focused on developing the mission concept and technology to enable the direct imaging of an Exo-Earth. However,
several key astronomical unknowns stand in the way of a fully optimized Exo-Earth imaging mission, the primary of
which is the uncertainty in the Exo-Zodi brightness. By analogy to our own Zodiacal dust, Exo-Zodiacal dust is
predicted to exist in the habitable zones of other stars, exactly in the locations where Exo-Earths would reside. Reflected
light from this dust could be a primary background contribution to measurements of the Exo-Earth.
We propose a mission concept called the Exo-Zodi Mapper (EZM) to obtain definitive measurements of the brightness
of the Exo-Zodi dust around target stars which are the prime targets for a future mission aimed at the direct detection of
Exo-Earths. Our mission concept uses a medium sized starshade that works with the James Webb Space Telescope to
image and characterize the brightness and distribution of Exo-Zodiacal dust around ~40 primary target stars. This
measurement would provide more precise requirements for the eventual Exo-Earth flagship mission, which may translate
into significant savings. In addition, EZM can provide a host of ancillary science information on these important targets,
including detailed maps of their dust distribution, studies of outer, giant planets, and exploration of the overall
architecture of these planetary systems. The EZM starshade can also be used to enable high-contrast imaging of other
targets of value to the astronomical community such as debris disks around young stars. We present an overview of the
science that motivated the mission concept, the driving requirements, and the top level mission architecture.
ExoPlanet/Coronagraphic Missions and Technology IV
SPICES: a 1.5-m space coronagraph for spectro-polarimetric characterization of cold exoplanets
Show abstract
The study of the physico-chemical properties of wide-separated exoplanets (> 1 AU) is a major goal of high-contrast
imaging techniques. SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary
Systems) is a project of space coronagraph dedicated to the spectro-polarimetric analysis of gas and ice giant
planets, super-Earths and circumstellar disks in visible light at a spectral resolution of about 40. After recalling
the science cases of the mission, we describe the optical design and the critical subsystems of the instrument.
We then discuss the SPICES performance that we derived from numerical simulations.
NEAT: a spaceborne astrometric mission for the detection and characterization of nearby habitable planetary systems
Show abstract
The NEAT (Nearby Earth Astrometric Telescope) mission is a proposal submitted to ESA for its 2010 call for M-size mission within the Cosmic Vision 2015-2025 plan. The main scientific goal of the NEAT mission is to detect and characterize planetary systems in an exhaustive way down to 1 Earth mass in the habitable zone and further away, around nearby stars for F, G, and K spectral types. This survey would provide the actual planetary masses, the full characterization of the orbits including their inclination, for all the components of the planetary system down to that mass limit. NEAT will continue the work performed by Hipparcos and Gaia by reaching a precision that is improved by two orders of magnitude on pointed targets.
Characterization of habitable exoplanets with simultaneous coronagraphy and astrometry with a single aperture telescope
Show abstract
With sub-microarcsecond astrometry, exoplanets can be identified and their masses measured. Coronagraphic imaging of
these exoplanets is required to study their atmospheres and surfaces in sufficient detail to identify possible signs of
biological activity. We show how both measurements can be simultaneously acquired with a single telescope in which
the central field is directed to a coronagraph instrument providing high contrast images, while the surrounding field is
imaged with a wide field camera in which numerous faint background stars are used as an astrometric reference. To
calibrate astrometric distortions due to optics and focal plane detector array imperfections and variations, we propose to
place small dark spots on the telescope primary mirror. The spots, arranged in a regular grid containing no low spatial
frequencies, do not affect the coronagraph performance. In the wide field image, they create diffraction spikes
originating from the central bright star, which are affected by changes in intrumental distortions in exactly the same way
as the background stars used for reference, thus allowing calibration of instrumental errors to micro-arcsecond level. We
show that combining simultaneous astrometric and coronagraphic measurements allows reliable detection and
characterization of exoplanets. Recent laboratory tests performed at the University of Arizona and NASA Ames validate
the concept, demonstrating both the ability to accurately calibrate astrometric distortions, and compatibility with high
contrast imaging systems.
Direct imaging of exoEarths embedded in clumpy debris disks
Show abstract
The inner solar system, where the terrestrial planets formed and evolve, is populated by small grains of dust
produced by collisions of asteroids and outgassing comets. At visible and infrared wavelengths, this dust cloud is
in fact the most luminous component in the solar system after the Sun itself and the Earth may appear similar to
a clump of zodiacal dust to an external observer. Hence, the presence of large amounts of dust in the habitable
zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of exoEarths
with future dedicated space-based telescopes. In that context, we address in this paper the detectability of
exoEarths embedded in structured debris disks with future space-based visible coronagraphs and mid-infrared
interferometers. Using a collisional grooming algorithm, we produce models of dust clouds that simultaneously
and self-consistently handle dust grain dynamics, including resonant interactions with planets, and grain-grain
collisions. Considering various viewing geometries, we also derive limiting dust densities that can be tolerated
around nearby main-sequence stars in order to ensure the characterization of exoEarths with future direct imaging
missions.
SPICA
The next-generation infrared space telescope SPICA
Show abstract
We present the overview and the current status of SPICA (Space Infrared Telescope for Cosmology and Astrophysics),
which is a mission optimized for mid- and far-infrared astronomy with a cryogenically cooled 3.2 m telescope. SPICA
has high spatial resolution and unprecedented sensitivity in the mid- and far-infrared, which will enable us to address a
number of key problems in present-day astronomy, ranging from the star-formation history of the universe to the
formation of planets. To reduce the mass of the whole mission, SPICA will be launched at ambient temperature and
cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system, a combination of which
allows us to have a 3-m class cooled (6 K) telescope in space with moderate total weight (3.7t). SPICA is proposed as a
Japanese-led mission together with extensive international collaboration. ESA's contribution to SPICA has been studied
under the framework of the ESA Cosmic Vision. The consortium led by SRON is in charge of a key focal plane
instrument SAFARI (SPICA Far-Infrared Instrument). Korea and Taiwan are also important partners for SPICA. US
participation to SPICA is under discussion. The SPICA project is now in the "risk mitigation phase". The target launch
year of SPICA is 2022.
Progress toward BLISS, the background-limited infrared-submillimeter spectrograph for SPICA
Show abstract
We are developing the Background-Limited Infrared-Submillimeter Spectrograph (BLISS) for SPICA to provide a breakthrough capability for far-IR survey spectroscopy. The 3.2-meter, actively-cooled (T<6K) SPICA telescope allows mid-IR to submm observations which are limited only by the natural backgrounds, and BLISS is designed
to operate near this fundamental limit. BLISS-SPICA provide a line sensitivity of 10-20 W m-2 , thereby enabling
spectroscopy of dust-obscured galaxies at all epochs back to the first billion years after the Big Bang (redshift
6), and study of all stages of planet formation in circumstellar disks.
BLISS covers the 35-430 micron waveband at moderate resolving power (300<R<700) in six grating spec trometer bands, each coupling at least two 2 sky positions simultaneously. The instrument is cooled with an on-board refrigerator to 50 mK for optimal sensitivity. The detector package in the goal implementation is 4200 silicon-nitride micro-mesh leg-isolated bolometers with superconducting transition-edge-sensed (TES) thermis tors, read out with a cryogenic time-domain multiplexer. The instrument is designed to fit within the stringent SPICA resource allocations for mass and heat lift, and to mitigate the impact of cosmic rays. We report on this design and our progress in prototyping and validating the BLISS spectrometers and prototype cooler. A companion paper in Conference 8452 (A. Beyer et al.) discusses in greater detail the progress in the BLISS TES bolometer development.
Mid-infrared camera and spectrometer on board SPICA
Show abstract
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for
mid- and far-infrared astronomy, envisioned for launch in early 2020s. The core wavelength coverage of this
mission is 5 to 200 micron. Mid-infrared Camera and Spectrometer (MCS) will provide imaging and spectroscopic
observing capabilities in the mid-infrared region with 4 modules. WFC (Wide Field Camera) has two 5
arcminutes square field of view and covers the wavelength range from 5 to 38 micron. MRS (Mid Resolution
Spectrometer) has integral field units by image slicer and covers the wavelength range from 12.2 to 37.5 micron
simultaneously using dichroic filter and two sets of spectrometers. HRS (High Resolution Spectrometer) covers
the wavelength range from 12 to 18 micron with resolving power 20000 to 30000, and it has optional short
wavelength channel which covers from 4 to 8 micron with resolving power 30000. LRS (Low Resolution Spectrometer)
adopts prism disperser and covers the wavelength range from 5 to 38 micron with resolving power 50
to 100. Here, we present detailed specifications of MCS, optical design, and estimated performance on orbit.
The SAFARI imaging spectrometer for the SPICA space observatory
Show abstract
The Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA, will provide astronomers with a long
awaited new window on the universe. Having a large cold telescope cooled to only 6K above absolute zero, SPICA will
provide a unique environment where instruments are limited only by the cosmic background itself. A consortium of
European and Canadian institutes has been established to design and implement the SpicA FAR infrared Instrument
SAFARI, an imaging spectrometer designed to fully exploit this extremely low far infrared background environment
provided by the SPICA observatory.
SAFARI’s large instantaneous field of view combined with the extremely sensitive Transition Edge Sensing detectors
will allow astronomers to very efficiently map large areas of the sky in the far infrared – in a square degree survey of a
1000 hours many thousands of faint sources will be detected, and a very large fraction of these sources will be fully
spectroscopically characterised by the instrument. Efficiently obtaining such a large number of complete spectra is
essential to address several fundamental questions in current astrophysics: how do galaxies form and evolve over cosmic
time?, what is the true nature of our own Milky Way?, and why and where do planets like those in our own solar system
come into being?
The optical design concept of SPICA-SAFARI
Show abstract
The Safari instrument on the Japanese SPICA mission is a zodiacal background limited imaging spectrometer offering a
photometric imaging (R ≈ 2), and a low (R = 100) and medium spectral resolution (R = 2000 at 100 μm) spectroscopy
mode in three photometric bands covering the 34-210 μm wavelength range. The instrument utilizes Nyquist sampled
filled arrays of very sensitive TES detectors providing a 2’x2’ instantaneous field of view. The all-reflective optical
system of Safari is highly modular and consists of an input optics module containing the entrance shutter, a calibration
source and a pair of filter wheels, followed by an interferometer and finally the camera bay optics accommodating the
focal-plane arrays. The optical design is largely driven and constrained by volume inviting for a compact three-dimensional
arrangement of the interferometer and camera bay optics without compromising the optical performance
requirements associated with a diffraction- and background-limited spectroscopic imaging instrument. Central to the
optics we present a flexible and compact non-polarizing Mach-Zehnder interferometer layout, with dual input and output
ports, employing a novel FTS scan mechanism based on magnetic bearings and a linear motor. In this paper we discuss
the conceptual design of the focal-plane optics and describe how we implement the optical instrument functions, define
the photometric bands, deal with straylight control, diffraction and thermal emission in the long-wavelength limit and
interface to the large-format FPA arrays at one end and the SPICA telescope assembly at the other end.
Euclid/WFIRST
Euclid: ESA's mission to map the geometry of the dark universe
Show abstract
Euclid is a space-borne survey mission developed and operated by ESA. It is designed to understand the origin of the
Universe's accelerating expansion. Euclid will use cosmological probes to investigate the nature of dark energy, dark
matter and gravity by tracking their observational signatures on the geometry of the Universe and on the history of
structure formation. The mission is optimised for the measurement of two independent cosmological probes: weak
gravitational lensing and galaxy clustering. The payload consists of a 1.2 m Korsch telescope designed to provide a large
field of view. The light is directed to two instruments provided by the Euclid Consortium: a visual imager (VIS) and a
near-infrared spectrometer-photometer (NISP). Both instruments cover a large common field of view of 0.54 deg2, to be
able to survey at least 15,000 deg2 for a nominal mission of 6 years. An overview of the mission will be presented: the
scientific objectives, payload, satellite, and science operations. We report on the status of the Euclid mission with a
foreseen launch in 2019.
VIS: the visible imager for Euclid
Show abstract
Euclid-VIS is a large format visible imager for the ESA Euclid space mission in their Cosmic Vision program, scheduled
for launch in 2019. Together with the near infrared imaging within the NISP instrument it forms the basis of the weak
lensing measurements of Euclid. VIS will image in a single r+i+z band from 550-900 nm over a field of view of ~0.5
deg2. By combining 4 exposures with a total of 2240 sec, VIS will reach to V=24.5 (10σ) for sources with extent ~0.3
arcsec. The image sampling is 0.1 arcsec. VIS will provide deep imaging with a tightly controlled and stable point spread
function (PSF) over a wide survey area of 15000 deg2 to measure the cosmic shear from nearly 1.5 billion galaxies to
high levels of accuracy, from which the cosmological parameters will be measured. In addition, VIS will also provide a
legacy imaging dataset with an unprecedented combination of spatial resolution, depth and area covering most of the
extra-Galactic sky. Here we will present the results of the study carried out by the Euclid Consortium during the Euclid
Definition phase.
Euclid near-infrared spectrophotometer instrument concept at the end of the phase A study
Show abstract
The Euclid mission objective is to map the geometry of the dark Universe by investigating the distance-redshift
relationship and the evolution of cosmic structures. The NISP (Near Infrared Spectro-Photometer) is one of the two
Euclid instruments operating in the near-IR spectral region (0.9-2μm). The instrument is composed of:
- a cold (140K) optomechanical subsystem constituted by a SiC structure, an optical assembly, a filter wheel
mechanism, a grism wheel mechanism, a calibration unit and a thermal control
- a detection subsystem based on a mosaic of 16 Teledyne HAWAII2RG 2.4μm. The detection subsystem is
mounted on the optomechanical subsystem structure
- a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an
instrument control unit.
This presentation will describe the architecture of the instrument, the expected performance and the technological key
challenges. This paper is presented on behalf of the Euclid Consortium.
The optical baseline concept of the NISP near infrared spectrometer and photometer on board of the ESA/EUCLID satellite
Show abstract
The ESA/EUCLID satellite is equipped with two instruments that are simultaneously observing patches of > 0:5 square degree on the sky. The VIS visual light high spacial resolution imager and the NISP near infrared spectrometer and photometer are separated by a di-chroic beam splitter. This paper shows the baseline concept of the NISP instrument with its two observational modes being low resolution slit-less spectroscopy and three band J, H and K+ photometry. The drivers for the optical design, the nominal performance as well as the tolerancing approach for NISP are being presented. The impact of the tolerance approach and the tight tolerances on the opto-mechanical design, assembly, integration and verification is addressed in a special section of this paper.
First optical tests of the Euclid grisms made by photolithography
Show abstract
The ESA mission Euclid is designed to explore the dark side of the Universe and to understand the nature of the dark energy responsible of the accelerating expansion of the Universe. One of the two probes carried by this mission is based on the Baryonic Acoustic Oscillation (BAO) method that requires the redshift measurements of millions of galaxies. In the Euclid design the spectroscopic channel uses slitless low resolution grisms. Classical grisms, manufactured by replication of a ruled master on the hypotenuse of a prism, are extremely difficult to make for Euclid due to the combination of low groove density and small blaze angle. Two years ago we started an RandD program to develop grisms by the photolithography process that is well adapted to coarse gratings and allows introducing aberration correction by ruling curved and non parallel grooves. During the Euclid Phase A, we developed several prototypes made by photolithography and we present in this paper the test results done in the specific environment of the Euclid mission.
Euclid Mission: building of a reference survey
Show abstract
Euclid is an ESA Cosmic-Vision wide-field-space mission which is designed to explain the origin of the acceleration of
Universe expansion. The mission will investigate at the same time two primary cosmological probes: Weak gravitational
Lensing (WL) and Galaxy Clustering (in particular Baryon Acoustic Oscillations, BAO). The extreme precision
requested on primary science objectives can only be achieved by observing a large number of galaxies distributed over
the whole sky in order to probe the distribution of dark matter and galaxies at all scales. The extreme accuracy needed
requires observation from space to limit all observational biases in the measurements. The definition of the Euclid
survey, aiming at detecting billions of galaxies over 15 000 square degrees of the extragalactic sky, is a key parameter of
the mission. It drives its scientific potential, its duration and the mass of the spacecraft. The construction of a Reference
Survey derives from the high level science requirements for a Wide and a Deep survey. The definition of a main
sequence of observations and the associated calibrations were indeed a major achievement of the Definition Phase.
Implementation of this sequence demonstrated the feasibility of covering the requested area in less than 6 years while
taking into account the overheads of space segment observing and maneuvering sequence. This reference mission will be
used for sizing the spacecraft consumables needed for primary science. It will also set the framework for optimizing the
time on the sky to fulfill the primary science and maximize the Euclid legacy.
Wavefront sensing for WFIRST with a linear optical model
Show abstract
In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations
in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model
is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical
alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at
different field points and does not require separate convergence of phase retrieval at individual field points. Because the
algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore,
because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus
to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance
wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field
Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical
model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise
and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using
these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use
them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the
accuracy of galactic ellipticity determination for weak-lensing science.
Euclid NISP GWA and compensating mechanism
Show abstract
This paper presents the GWA and the Compensating mechanism of the Near Infrared SpectroPhotometer (NISP) instrument of the ESA Euclid mission. The NIS instrument should perform an exposure sequence in the wave length range [0.9 - 2.0Jum with different exposures of the same field of views with different passband grisms with two orthogonal dispersion directions and two wavelength range. These functionalities will be achieved by a mechanism supporting the optical elements: the Grism Wheel Assembly (GWA). The required positioning repeatability is in the order of few arcsec to keep the spectra aligned with the detector pixel columns/rows. The GWA will be assembled to the NISP Optomechanical Assembly (NIOMA) with an operating temperature of 140K. A further mechanism is necessary to compensate the torque perturbances induced by the two large wheels. It is based onto a stepper motor that will drive a flywheel.
Small Missions/Explorers I
Summary of observations of the infrared camera (IRC) onboard AKARI
Show abstract
AKARI, the Japanese satellite mission dedicated to infrared astronomy was launched in 2006 February and exhausted its liquid helium in 2007 August. During the cold mission phase, the Infrared Camera (IRC) onboard carried out an all-sky survey at 9 and 18µm with better spatial resolution and higher sensitivity than IRAS. Both bands also have slightly shorter wavelength coverage than IRAS 12 and 25μm bands and thus provide different information on the infrared sky. All-sky image data of the IRC are now in the final processing and will be released to the public within a year. After the exhaustion of the cryogen, the telescope and focal plane instruments of AKARI had still been kept at sufficiently low temperatures owing to the onboard cryocooler. Near-infrared (NIR) imaging and spectroscopic observations with the IRC had continued until 2011 May, when the spacecraft had a serious problem in the power supply system that forced us to terminate the observation. The IRC carried out nearly 20000 pointing observations in total despite of its near-earth orbit. About a half of them were performed after the exhaustion of the cryogen in the spectroscopic modes, which provided high-sensitivity NIR spectra from 2 to 5µm without disturbance of the terrestrial atmosphere. During the warm mission phase, the temperature of the instrument gradually increased and changed the array operation conditions. We present a summary of AKARI/IRC observations, including the all-sky mid-infrared diffuse data as well as the data taken in the warm mission phase.
Breakthrough capability for the NASA astrophysics explorer program: reaching the darkest sky
Show abstract
We describe a mission architecture designed to substantially increase the science capability of the NASA Science
Mission Directorate (SMD) Astrophysics Explorer Program for all AO proposers working within the near-UV to far-infrared
spectrum. We have demonstrated that augmentation of Falcon 9 Explorer launch services with a 13 kW Solar
Electric Propulsion (SEP) stage can deliver a 700 kg science observatory payload to extra-Zodiacal orbit. This new
capability enables up to ~13X increased photometric sensitivity and ~160X increased observing speed relative to a Sun-
Earth L2, Earth-trailing, or Earth orbit with no increase in telescope aperture. All enabling SEP stage technologies for
this launch service augmentation have reached sufficient readiness (TRL-6) for Explorer Program application in
conjunction with the Falcon 9. We demonstrate that enabling Astrophysics Explorers to reach extra-zodiacal orbit will
allow this small payload program to rival the science performance of much larger long development time systems; thus,
providing a means to realize major science objectives while increasing the SMD Astrophysics portfolio diversity and
resiliency to external budget pressure. The SEP technology employed in this study has strong applicability to SMD
Planetary Science community-proposed missions. SEP is a stated flight demonstration priority for NASA's Office of the
Chief Technologist (OCT). This new mission architecture for astrophysics Explorers enables an attractive realization of
joint goals for OCT and SMD with wide applicability across SMD science disciplines.
CASTOR: the Cosmological Advanced Survey Telescope for Optical and Ultraviolet Research
Show abstract
The Cosmological Advanced Survey Telescope for Optical and UV Research (CASTOR) is a proposed CSA
mission that would make a unique, powerful, and lasting contribution to astrophysics by providing panoramic,
high-resolution imaging in the UV/optical (0.15 - 0.55 μm) spectral region. This versatile `smallSAT'-class
mission would far surpass any ground-based optical telescope in terms of angular resolution, and would provide
ultra-deep imaging in three broad lters to supplement longer-wavelength data from planned international dark
energy missions (Euclid, WFIRST) as well as from the ground-based Large Synoptic Survey Telescope (LSST).
Combining the largest focal plane ever
own in space, with an innovative optical design that delivers HST-quality
images over a eld two orders of magnitude larger than Hubble Space Telescope (HST), CASTOR would image
about 1/8th of the sky to a (u-band) depth ~1 magnitude fainter than will be possible with LSST even after a
decade of operations. No planned or proposed astronomical facility would exceed CASTOR in its potential for
discovery at these wavelengths.
Small Missions/Explorers II
LiteBIRD: a small satellite for the study of B-mode polarization and inflation from cosmic background radiation detection
Show abstract
LiteBIRD [Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background
Radiation Detection] is a small satellite to map the polarization of the cosmic microwave background (CMB)
radiation over the full sky at large angular scales with unprecedented precision. Cosmological inflation, which
is the leading hypothesis to resolve the problems in the Big Bang theory, predicts that primordial gravitational
waves were created during the inflationary era. Measurements of polarization of the CMB radiation are known as
the best probe to detect the primordial gravitational waves. The LiteBIRD working group is authorized by the
Japanese Steering Committee for Space Science (SCSS) and is supported by JAXA. It has more than 50 members
from Japan, USA and Canada. The scientific objective of LiteBIRD is to test all the representative inflation models that satisfy single-field slow-roll conditions and lie in the large-field regime. To this end, the requirement
on the precision of the tensor-to-scalar ratio, r, at LiteBIRD is equal to or less than 0.001. Our baseline design
adopts an array of multi-chroic superconducting polarimeters that are read out with high multiplexing factors in
the frequency domain for a compact focal plane. The required sensitivity of 1.8μKarcmin is achieved with 2000
TES bolometers at 100mK. The cryogenic system is based on the Stirling/JT technology developed for SPICA,
and the continuous ADR system shares the design with future X-ray satellites.
WISH for deep and wide NIR surveys
Toru Yamada,
Ikuru Iwata,
Makiko Ando,
et al.
Show abstract
WISH, Wide-field Imaging Surveyor for High-redshiftt, is a space mission concept to conduct very deep and widefield
surveys at near infrared wavelength at 1-5μm to study the properties of galaxies at very high redshift beyond the
epoch of cosmic reionization. The concept has been developed and studied since 2008 to be proposed for future
JAXA/ISAS mission. WISH has a 1.5m-diameter primary mirror and a wide-field imager covering 850 arcmin2. The
pixel scale is 0.155 arcsec for 18μm pitch, which properly samples the diffraction-limited image at 1.5μm. The main
program is Ultra Deep Survey (UDS) covering 100 deg2 down to 28AB mag at least in five broad bands. We expect to
detect <104 galaxies at z=8-9, 103-104 galaxies at z=11-12, and 50-100 galaxies at z<14, many of which can be feasible
targets for deep spectroscopy with Extremely Large Telescopes. With recurrent deep observations, detection and light
curve monitoring for type-Ia SNe in rest-frame infrared wavelength is also conducted, which is another main science
goal of the mission. During the in-orbit 5 years observations, we expect to detect and monitor <2000 type-Ia SNe up to
z~2. WISH also conducts Ultra Wide Survey, covering 1000deg2 down to 24-25AB mag as well as Extreme Survey,
covering a limited number of fields of view down to 29-30AB mag. We here report the progress of the WISH project
including the basic telescope and satellite design as well as the results of the test for a proto-model of the flip-type filter
exchanger which works robustly near 100K.
The i-INSPIRE satellite: a university pico-satellite project
Lisa M. R. Fogarty,
Size Z. (A.) Xiao,
Jiro Funamoto,
et al.
Show abstract
The i-INSPIRE satellite is the result of a collaborative project at the University of Sydney, across the science
and engineering faculties. The satellite is a compact tube-shaped pico-satellite with a mass of less than 0.75 kg.
i-INSPIRE carries three science instruments - a photonic spectrograph, a radiation counter and an imaging
camera, and will be launched to a 310km polar orbit in late 2012 or early 2013. Here we describe the satellite
and its subsystems (including the science instruments and the communication system) as well as the ground
station, pre-launch tests, and the proposed launch itself. i-INSPIRE will be Australia's first fully university
operated pico-satellite.
FalconSAT-7: a membrane photon sieve CubeSat solar telescope
Show abstract
We are currently constructing FalconSAT-7 for launch in mid-2014. The low-Earth, 3U CubeSat solar telescope
incorporates a 0.2m deployable membrane photon sieve with over 2.5 billion holes. The aim of the experiment is to
demonstrate diffraction limited imaging of a collapsible, diffractive primary over a narrow bandwidth. As well as being
simpler to manufacture and deploy than curved, polished surfaces, the sheets do not have to be optically flat, greatly
reducing many engineering issues. As such, the technology is particularly promising as a means to achieve extremely
large optical primaries from compact, lightweight packages.
A conceptual design of a near infrared satellite for PAH survey
Chun Xu,
Jinsong Deng,
Yonghe Zhang
Show abstract
We present here a conceptual design of a near infrared survey satellite whose primary goal is to carry out an all sky
survey of Polycyclic Aromatic Hydrocarbons (PAH). The searching of PAH is through direct imaging both at and
besides its 3.3 μm CH stretching vibrations emission bands and make comparison between the "line" and the continuum
fluxes. The dawn-dust sun-synchronous orbit is chosen because it is ideal for thermal control and it is suitable for all sky
surveys. The "pointing-maneuver-pointing" observing strategy is adopted in order to minimize the effect from the
detector read noises. The survey sensitivity is chosen to generally match those of the UKIDSS near IR surveys so their
results can be compared more directly.
ECHO
The Exoplanet Characterization Observatory (EChO): performance model EclipseSim and applications
Show abstract
We present EclipseSim, a radiometric model for exoplanet transit spectroscopy that allows easy exploration of
the fundamental performance limits of any space-based facility aiming to perform such observations. It includes
a library of stellar model atmosphere spectra and can either approximate exoplanet spectra by simplified models,
or use any theoretical or observed spectrum, to simulate observations. All calculations are done in a spectrally
resolved fashion and the contributions of the various fundamental noise sources are budgeted separately, allowing
easy assessment of the dominant noise sources, as a function of wavelength. We apply EclipseSim to the Exoplanet
Characterization Observatory (EChO), a proposed mission dedicated to exoplanet transit spectroscopy that is
currently in competition for the M3 launch slot of ESA’s cosmic vision programme. We show several case studies
on planets with sizes in the super-Earth to Jupiter range, and temperatures ranging from the temperate to the
≈1500K regime, demonstrating the power and versatility of EChO. EclipseSim is publicly available.*
An integrated payload design for the Exoplanet Characterisation Observatory (EChO)
Show abstract
The Exoplanet Characterisation Observatory (EChO) is a space mission dedicated to undertaking spectroscopy of
transiting exoplanets over the widest wavelength range possible. It is based around a highly stable space platform with a
1.2 m class telescope. The mission is currently being studied by ESA in the context of a medium class mission within
the Cosmic Vision programme for launch post 2020. The payload suite is required to provide simultaneous coverage
from the visible to the mid-infrared and must be highly stable and effectively operate as a single instrument. In this
paper we describe the integrated spectrometer payload design for EChO which will cover the 0.4 to 16 micron
wavelength band. The instrumentation is subdivided into 5 channels (Visible/Near Infrared, Short Wave InfraRed, 2 x Mid Wave InfraRed; Long Wave InfraRed) with a common set of optics spectrally dividing the input beam via dichroics.
We discuss the significant design issues for the payload and the detailed technical trade-offs that we are undertaking to
produce a payload for EChO that can be built within the mission and programme constraints and yet which will meet the
exacting scientific performance required to undertake transit spectroscopy.
Visible/infrared spectrometer for EChO
Show abstract
The Exoplanet Characterisation Observatory (EChO) is a medium class mission candidate within ESA's Cosmic Vision
2015-2025 program on space science. EChO will be equipped with a visible to infrared spectrometer covering the
wavelength range from 0.4 - 11 μm (goal: 16 μm) at a spectral resolving power between 30 and 300 in order to
characterize the atmospheres of known transiting extrasolar planets ranging from Hot Jupiters to Super Earths. In this
paper we will present first results from the dedicated study of the EChO science payload carried out by our EChO
Instrument Consortium during the assessment phase of the mission.
Design of the MWIR channels of EChO
Show abstract
In this paper, we present the design of the MWIR channels of EChO. Two channels cover the 5-11 micron spectral
range. The choice of the boundaries of each channel is a trade-off driven by the science goals (spectral features of key
molecules) and several parameters such as the common optics design, the dichroic plates design, the optical materials
characteristics, the detector cut-off wavelength. We also will emphasize the role of the detectors choice that drives the
thermal and mechanical designs and the cooling strategy.
Technology
Mirror coatings with atomic layer deposition: initial results
Show abstract
The technology of Atomic Layer Deposition (ALD) holds promise to enable a future strategic mission that can address both ultraviolet (UV) astrophysics and optical exoplanet science with a shared telescope. The technology path to a shared telescope requires the development of a mirror coating with high reflectance from 100 nm to 1000 nm, and low polarization effects (i.e., s-p phase shifts that can vary with angle of incidence across a primary and secondary mirror) in the optical range. Currently, UV coatings have low reflectance, and conventional optical coatings have poor polarization properties for high-contrast coronagraph applications. In this paper we attempt to take a first step toward solving both problems simultaneously by using ALD, taking advantage of the fact that ALD can potentially produce mirror coatings with denser layers than conventional coatings (hence better reflectance, durability, and water resistance). In addition, ALD can potentially produce coatings with new composite materials (hence better control of polarization). We report here the results of our initial experiments with mirror coatings using ALD.
The thermal sieve: a diffractive baffle that provides thermal isolation of a cryogenic optical system from an ambient temperature collimator
Show abstract
We present the thermal sieve, which is a diffractive baffle that provides thermal isolation between an
ambient collimator and a cryogenic optical system being measured. The baffle uses several parallel
plates with holes in them. The holes are lined up to allow the collimated light to pass, but the view
factor for thermal radiation is greatly reduced. A particular design is shown here that allows less than
0.25 W/m2 thermal transfer and degrades the test wavefront by only 3 nm rms.
Innovative optical setup for testing a stereo camera for space applications
Show abstract
The Stereo Camera (STC) of the SIMBIO-SYS imaging suite of the BepiColombo ESA mission to Mercury is based on
an innovative and compact design in which the light independently collected by two optical channels at ±20° separation
with respect to nadir falls on a common bidimensional detector. STC adopts a novel stereo acquisition mode, based on
the push-frame concept, never used before on a space mission. To characterize this camera for obtaining the most
accurate data of the Mercury surface, standard calibration measurements have been performed. In addition, we also
wanted to demonstrate and characterize the capability of the instrument to reconstruct a 3D surface with the desired
accuracy by means of the stereo push-frame concept. To this end, a lab setup has been realized with an evaluation model
of STC, in which the problem of working at an essentially infinite object distance over hundred km baselines has been
overcome by means of a simple collimator and two precision rotators. The intrinsic and extrinsic parameters of the
camera have been obtained with standard stereo procedures, adapted to the specific case. The stereo validation has been
performed by comparing the shape of the target object accurately measured by laser scanning, with the shape
reconstructed by applying the adopted stereo algorithm to the acquired image pairs. The obtained results show the
goodness of this innovative validation technique, that will be applied also for validating the stereo capabilities of STC
flight model.
Astrometry/GAiA
A metrology concept for multiple telescope astrometry
Show abstract
Medium to large angle observations, e.g. for global astrometry, can be implemented in space by means of either a
common telescope, fed by a Beam Combiner (as in Hipparcos), or by individual telescopes set in a rigid geometry
(as in Gaia). We investigate the applicability of auto-collimation and cophasing techniques for implementation of
a monitoring system alternative to more conventional point-to-point metrology. Apart different implementation
constraints, the most relevant difference consists in the auto-collimation approach characteristics of monitoring
simultaneously comparably large sections of the optical system, thus evaluating collective properties closer to
those experienced by the stellar beams.
Gaia's FPA: sampling the sky in silicon
Show abstract
ESA´s astrometry satellite Gaia is scheduled for launch in 2013. In a combination of outstanding hardware performance,
autonomous object detection and sophisticated data processing, Gaia will chart more than a billion stars of the entire sky
to unprecedented accuracy during its 5 years mission. A key element to its mission success is the focal plane assembly
(FPA), the largest ever flown to space, comprising a close-butted almost Giga-pixel mosaic of 106 large area CCDs.
Manufacturing and extensive testing of the individual devices and detector system units as well as integration on the
single-piece, silicon-carbide support structure has been a challenge. The focal plane is now assembled and has undergone
its final tests during 2012.
The paper summarizes the expected in-flight performances of Gaia´s FPA and the implemented tools and procedures to
monitor its operation in space. Accurate knowledge of the impact of FPA performance parameters on individual
measurements and its evolution in time is critical to achieve the high accuracy needed in calibrating the science data. An
example is the radiation-induced deterioration of the CCD charge transfer efficiency, which acts on distorting the
detected object PSFs while observing the sky in continuous scan mode. Through dedicated calibration procedures and
directly through the scientific data processing, Gaia will therefore closely track the radiation environment at L2 from the
FPA output itself. Detection of transient effects and analysis of persistent damage on the CCDs mainly caused by solar
protons converts Gaia's FPA inherently into the largest ever radiation monitor in space.
Gaia in-orbit realignment: overview and data analysis
Show abstract
The ESA Gaia spacecraft has two Shack-Hartmann wavefront sensors (WFS) on its focal plane. They are
required to refocus the telescope in-orbit due to launch settings and gravity release. They require bright stars to
provide good signal to noise patterns. The centroiding precision achievable poses a limit on the minimum stellar
brightness required and, ultimately, on the observing time required to reconstruct the wavefront. Maximum
likelihood algorithms have been developed at the Gaia SOC. They provide optimum performance according to
the Crámer-Rao lower bound. Detailed wavefront reconstruction procedures, dealing with partial telescope pupil
sampling and partial microlens illumination have also been developed. In this work, a brief overview of the WFS
and an in depth description of the centroiding and wavefront reconstruction algorithms is provided.
Gaia basic angle monitoring system
Show abstract
The Gaia mission will create an extraordinarily precise three-dimensional map of more than one billion stars in our
Galaxy. The Gaia spacecraft, built by EADS Astrium, is part of ESA's Cosmic Vision programme and scheduled for
launch in 2013. Gaia measures the position, distance and motion of stars with an accuracy of 24 micro-arcsec using two
telescopes at a fixed mutual angle of 106.5°, named the ‘Basic Angle’. This accuracy requires ultra-high stability, which
can only be achieved by using Silicon Carbide for both the optical bench and the telescopes. TNO has developed, built
and space qualified the Silicon carbide Basic Angle Monitoring (BAM) on-board metrology system for this mission.
The BAM measures the relative motion of Gaia’s telescopes with accuracies in the range of 0.5 micro-arcsec. This is
achieved by a system of two laser interferometers able to measure Optical Path Differences (OPD) as small as 1.5
picometer rms. Following a general introduction to the Gaia mission, the Payload Module (PLM) and the use of Silicon
Carbide as base material, this presentation will address an overview of the challenges towards the key requirements,
design, integration and testing (including space-level qualification) of the Gaia BAM.
Exoplanet and Combined Missions
The EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE)
Show abstract
We present an overview of the EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE), selected by
NASA for technology development and maturation. EXCEDE will study the formation, evolution and architectures of
exoplanetary systems, and characterize circumstellar environments into stellar habitable zones. EXCEDE provides
contrast-limited scattered-light detection sensitivities ~ 1000x greater than HST or JWST coronagraphs at a much
smaller effective inner working angle (IWA), thus enabling the exploration and characterization of exoplanetary
circumstellar disks in currently inaccessible domains. EXCEDE will utilize a laboratory demonstrated high-performance
Phase Induced Amplitude Apodized Coronagraph (PIAA-C) integrated with a 70 cm diameter unobscured aperture
visible light telescope. The EXCEDE PIAA-C will deliver star-to-disk augmented image contrasts of < 10E-8 and a 1.2
λ/D IWA or 0.14” with a wavefront control system utilizing a 2000-element MEMS DM and fast steering mirror.
EXCEDE will provide 0.12” spatial resolution at 0.4 μm with dust detection sensitivity to levels of a few tens of zodis
with two-band imaging polarimetry. EXCEDE is a science-driven technology pathfinder that will advance our
understanding of the formation and evolution of exoplanetary systems, placing our solar system in broader astrophysical
context, and will demonstrate the high contrast technologies required for larger-scale follow-on and multi-wavelength
investigations on the road to finding and characterizing exo-Earths in the years ahead.
Using the ISS as a testbed to prepare for the next generation of space-based telescopes
Show abstract
The infrastructure available on the ISS provides a unique opportunity to develop the technologies necessary to assemble
large space telescopes. Assembling telescopes in space is a game-changing approach to space astronomy. Using the ISS
as a testbed enables a concentration of resources on reducing the technical risks associated with integrating the
technologies, such as laser metrology and wavefront sensing and control (WFSandC), with the robotic assembly of major
components including very light-weight primary and secondary mirrors and the alignment of the optical elements to a
diffraction-limited optical system in space. The capability to assemble the optical system and remove and replace
components via the existing ISS robotic systems such as the Special Purpose Dexterous Manipulator (SPDM), or by the
ISS Flight Crew, allows for future experimentation as well as repair if necessary. In 2015, first light will be obtained by
the Optical Testbed and Integration on ISS eXperiment (OpTIIX), a small 1.5-meter optical telescope assembled on the
ISS. The primary objectives of OpTIIX include demonstrating telescope assembly technologies and end-to-end optical
system technologies that will advance future large optical telescopes.
Wide Field Infrared Survey Telescope [WFIRST]: telescope design and simulated performance
Show abstract
The Wide Field Infrared Survey Telescope (WFIRST) mission concept was ranked first in new space astrophysics
missions by the Astro2010 Decadal Survey, incorporating the Joint Dark Energy Mission payload concept and multiple
science white papers. This mission is based on a space telescope at L2 studying exoplanets [via gravitational
microlensing], probing dark energy, and surveying the near infrared sky. Since the release of the Astro2010 Decadal
Survey, the team has been working with the WFIRST Science Definition Team to refine mission and payload concepts.
We present the current interim reference mission point design of the payload, based on the use of a 1.3m unobscured
aperture three mirror anastigmat form, with focal imaging and slit-less spectroscopy science channels. We also present
the first results of Structural/Thermal/Optical performance modeling of the telescope point design.
Hubble Space Telescope SM4/Spitzer
Performance and calibration of the HST Wide Field Camera 3
Show abstract
The WFC3 is the primary science instrument on HST. It accounts for over half of all observations since its installation
during SM4 in May 2009. We discuss the evolution of our understanding of the performance of WFC3 and our
calibration strategies. A key aspect of WFC3 is its high degree of stability which permits steadily improving calibrations.
We discuss four main topics: the calibration and trending of photometric and astrometric observations, the techniques we
are using to achieve markedly improved flat field calibrations (and their associated challenges), the evolution of the
WFC3 CCD and HgCdTe detectors in the space environment, and the recent implementation of a spatial scanning
observing technique which enables very high signal to noise ratio observations of bright sources including exo-planets
and also high precision astrometry.
Characterizing persistence in the IR detector within the Wide Field Camera 3 instrument on the Hubble Space Telescope
Show abstract
Like essentially all IR arrays, the IR detector in the Wide Field Camera 3 (WFC3) instrument on-board Hubble Space
Telescope (HST) exhibits afterimages, known as persistence, following exposures to light levels that approach or
exceed saturation of individual pixels of the detector. The nature of the persistence in the HgCdTe WFC3/IR detector is
distinctly non-linear in that the amount of persistence is not simply proportional to the exposure level. Instead, the
amount of persistence is small until the exposure reaches about half saturation at which point it rises fairly rapidly until
the exposure reaches about twice saturation and then it increases gradually with increasing saturation. The persistence
shows typical power law decay with time over the periods of time that are relevant to HST observations. Given the
frequent usage of the WFC3/IR detector on HST, it is not possible to completely avoid the effects of persistence in
observations obtained with HST by introducing time gaps between IR observations. Therefore, we have developed a
parameterized persistence model that we are using to estimate the amount of persistence in all WRC3/IR images. These
estimates are available for all existing WFC3/IR images through the Mikulski Archive at STScI (MAST) to help HST
users remove persistence from their images. Here we discuss the characterization of persistence in the WFC3 detector in
orbit, the fraction of observations that are affected by persistence, and the effectiveness of the tools we have developed
to reduce the effects of persistence in WFC3 images.
A Spitzer IRAC measure of the zodiacal light
Show abstract
The dominant non-instrumental background source for space-based infrared observatories is the zodiacal light
(ZL). We present Spitzer Infrared Array Camera (IRAC) measurements of the ZL at 3.6, 4.5, 5.8, and 8.0 μm,
taken as part of the instrument calibrations. We measure the changing surface brightness levels in approximately
weekly IRAC observations near the north ecliptic pole over the period of roughly 8.5 years. This long time
baseline is crucial for measuring the annual sinusoidal variation in the signal levels due to the tilt of the dust disk
with respect to the ecliptic, which is the true signal of the ZL. This is compared to both Cosmic Background
Explorer Diffuse Infrared Background Experiment data and a ZL model based thereon. Our data show a few
percent discrepancy from the Kelsall et al.(1998)1 model including a potential warping of the interplanetary dust
disk and a previously detected overdensity in the dust cloud directly behind the Earth in its orbit. Accurate
knowledge of the ZL is important for both extragalactic and Galactic astronomy including measurements of the
cosmic infrared background, absolute measures of extended sources, and comparison to extrasolar interplanetary
dust models. IRAC data can be used to further inform and test future ZL models.
Intra-pixel gain variations and high-precision photometry with the Infrared Array Camera (IRAC)
Show abstract
The Infrared Array Camera (IRAC) on the Spitzer Space Telescope has been used to measure < 10-4 temporal
variations in point sources (such as transiting extrasolar planets) at 3.6 and 4.5 μm. Due to the under-sampled
nature of the PSF, the warm IRAC arrays show variations of as much as 8% in sensitivity as the center of the
PSF moves across a pixel due to normal spacecraft pointing wobble and drift. These intra-pixel gain variations
are the largest source of correlated noise in IRAC photometry. Usually this effect is removed by fitting a
model to the science data themselves (self-calibration), which could result in the removal of astrophysically
interesting signals. We describe a new technique for significantly reducing the gain variations and improving
photometric precision in a given observation, without using the data to be corrected. This comprises: (1) an
adaptive centroiding and repositioning method ("Peak-Up") that uses the Spitzer Pointing Control Reference
Sensor (PCRS) to repeatedly position a target to within 0.1 IRAC pixels of an area of minimal gain variation;
and (2) the high-precision, high-resolution measurement of the pixel gain structure using non-variable stars. We
show that the technique currently allows the reduction of correlated noise by almost an order of magnitude over
raw data, which is comparable to the improvement due to self-calibration. We discuss other possible sources of
correlated noise, and proposals for reducing their impact on photometric precision.
Absolute photometric calibration of IRAC: lessons learned using nine years of flight data
Show abstract
Significant improvements in our understanding of various photometric effects have occurred in the more than nine years
of flight operations of the Infrared Array Camera aboard the Spitzer Space Telescope. With the accumulation of
calibration data, photometric variations that are intrinsic to the instrument can now be mapped with high fidelity. Using
all existing data on calibration stars, the array location-dependent photometric correction (the variation of flux with
position on the array) and the correction for intra-pixel sensitivity variation (pixel-phase) have been modeled
simultaneously. Examination of the warm mission data enabled the characterization of the underlying form of the pixelphase
variation in cryogenic data. In addition to the accumulation of calibration data, significant improvements in the
calibration of the truth spectra of the calibrators has taken place. Using the work of Engelke et al. (2006), the KIII
calibrators have no offset as compared to the AV calibrators, providing a second pillar of the calibration scheme. The
current cryogenic calibration is better than 3% in an absolute sense, with most of the uncertainty still in the knowledge of
the true flux densities of the primary calibrators. We present the final state of the cryogenic IRAC calibration and a
comparison of the IRAC calibration to an independent calibration methodology using the HST primary calibrators.
Large Space Optics
Space active optics: performance of a deformable mirror for in-situ wave-front correction in space telescopes
Show abstract
MADRAS (Mirror Active, Deformable and Regulated for Applications in Space) project aims at demonstrating
the interest of Active Optics for space applications. We present the prototype of a 24 actuators, 100 mm diameter
deformable mirror to be included in a space telescope's pupil relay to compensate for large lightweight primary
mirror deformation. The mirror design has been optimized with Finite Element Analysis and its experimental
performance characterized in representative conditions. The developed deformable mirror provides an efficient
wave-front correction with a limited number of actuators and a design fitting space requirements.
MOIRE: initial demonstration of a transmissive diffractive membrane optic for large lightweight optical telescopes
Show abstract
The desire to field space-based telescopes with apertures in excess of 10 meter diameter is forcing the development
of extreme lightweighted large optics. Sparse apertures, shell optics, and membrane optics are a few of the
approaches that have been investigated and demonstrated. Membrane optics in particular have been investigated for
many years. The majority of the effort in membrane telescopes has been devoted to using reflective membrane
optics with a fair level of success being realized for small laboratory level systems; however, extending this
approach to large aperture systems has been problematic. An alternative approach in which the membrane is used as
a diffractive transmission element has been previously proposed, offering a significant relaxation in the control
requirements on the membrane surface figure. The general imaging principle has been demonstrated in 50-cm-scale
laboratory systems using thin glass and replicated membranes at long f-number (f/50). In addition, a 5-meter
diameter f/50 transmissive diffractive optic has been demonstrated, using 50-cm scale segments arrayed in a
foldable origami pattern. In this paper we discuss Membrane Optical Imager Real-time Exploitation (MOIRE)
Phase 1 developments that culminated in the development and demonstration of an 80 cm diameter, off-axis, F/6.5
phase diffractive transmissive membrane optic. This is a precursor for an optic envisioned as one segment of a 10
meter diameter telescope. This paper presents the demonstrated imaging wavefront performance and collection
efficiency of an 80 cm membrane optic that would be used in an F/6.5 primary, discusses the anticipated areal
density in relation to existing space telescopes, and identifies how such a component would be used in previously
described optical system architectures.
Spherical primary optical telescope (SPOT) segments
Show abstract
The spherical primary optical telescope (SPOT) project is an internal research and development program at NASA
Goddard Space Flight Center. The goals of the program are to develop a robust and cost effective way to
manufacture spherical mirror segments and demonstrate a new wavefront sensing approach for continuous phasing
across the segmented primary. This paper focuses on the fabrication of the mirror segments. Significant cost
savings were achieved through the design, since it allowed the mirror segments to be cast rather than machined from
a glass blank. Casting was followed by conventional figuring at Goddard Space Flight Center. After polishing, the
mirror segments were mounted to their composite assemblies. QED Technologies used magnetorheological
finishing (MRF®) for the final figuring. The MRF process polished the mirrors while they were mounted to their
composite assemblies. Each assembly included several magnetic invar plugs that extended to within an inch of the
face of the mirror. As part of this project, the interaction between the MRF magnetic field and invar plugs was
evaluated. By properly selecting the polishing conditions, MRF was able to significantly improve the figure of the
mounted segments. The final MRF figuring demonstrates that mirrors, in the mounted configuration, can be
polished and tested to specification. There are significant process capability advantes due to polishing and testing
the optics in their final, end-use assembled state.
The path to far-IR interferometry in space: recent developments, plans, and prospects
Show abstract
The far-IR astrophysics community is eager to follow up Spitzer and Herschel observations with sensitive, high-resolution
imaging and spectroscopy, for such measurements are needed to understand merger-driven star formation and
chemical enrichment in galaxies, star and planetary system formation, and the development and prevalence of water-bearing
planets. The community is united in its support for a space-based interferometry mission. Through concerted
efforts worldwide, the key enabling technologies are maturing. Two balloon-borne far-IR interferometers are presently
under development. This paper reviews recent technological and programmatic developments, summarizes plans, and
offers a vision for space-based far-IR interferometry involving international collaboration.
Update on multivariable parametric cost models for ground and space telescopes
Show abstract
Parametric cost models can be used by designers and project managers to perform relative cost comparisons between
major architectural cost drivers and allow high-level design trades; enable cost-benefit analysis for technology
development investment; and, provide a basis for estimating total project cost between related concepts. This paper
reports on recent revisions and improvements to our ground telescope cost model and refinements of our understanding
of space telescope cost models. One interesting observation is that while space telescopes are 50X to 100X more
expensive than ground telescopes, their respective scaling relationships are similar. Another interesting speculation is
that the role of technology development may be different between ground and space telescopes. For ground telescopes,
the data indicates that technology development tends to reduce cost by approximately 50% every 20 years. But for space
telescopes, there appears to be no such cost reduction because we do not tend to re-fly similar systems. Thus, instead of
reducing cost, 20 years of technology development may be required to enable a doubling of space telescope capability.
Other findings include: mass should not be used to estimate cost; spacecraft and science instrument costs account for
approximately 50% of total mission cost; and, integration and testing accounts for only about 10% of total mission cost.
Solar Missions
Design of large aperture solar optical telescope for the SOLAR-C mission
Y. Suematsu,
Y. Katsukawa,
H. Hara,
et al.
Show abstract
A large aperture optical telescope is planned for the next Japanese solar mission SOLAR-C as one of major three
observing instruments. The optical telescope is designed to provide high-angular-resolution investigation of lower
atmosphere from the photosphere to the uppermost chromosphere with enhanced spectroscopic and spectro-polarimetric
capability covering a wide wavelength region from 280 nm to 1100 nm. The opto-mechanical and -thermal performance
of the telescope is crucial to attain high-quality solar observations and we present a study of optical and structural design
of the large aperture space solar telescope, together with conceptual design of its accompanying focal plane instruments:
wide-band and narrow-band filtergraphs and a spectro-polarimeter for high spatial and temporal observations in the solar
photospheric and chromospheric lines useful for sounding physical condition of dynamical phenomena.
In-orbit determination of the straylight in the SOHO/LASCO-C2 coronagraph and its temporal evolution
Show abstract
The LASCO-C2 coronagraph aboard SOHO (the SOlar and Heliospheric Observatory) is continuously observing
the solar corona since early 1996. The instrument as well as the experimental context underwent during this
period many changes and observational constraints. The consequences for the in-orbit calibration procedures
are illustrated with the systematic measure of the coronagraph straylight. Disentangle the coronal signal and
the straylight is the crucial point. The separation and monitoring of the straylight component rely on the daily
sets of polarized observations of the corona and a minimal set of assumptions about the symmetry of the F-corona
(the dust component of the solar corona). Four main changes have been detected since 1996. Specific
recommendations for the in-orbit calibration of future spatial coronagraphs will be presented.
Optimization of the occulter for the Solar Orbiter/METIS coronagraph
Show abstract
METIS (Multi Element Telescope for Imaging and Spectroscopy investigation), selected to fly aboard the Solar Orbiter ESA/NASA mission, is conceived to perform imaging (in visible, UV and EUV) and spectroscopy (in EUV) of the solar corona, by means of an integrated instrument suite located on a single optical bench and sharing the same aperture on the satellite heat shield. As every coronagraph, METIS is highly demanding in terms of stray light suppression. Coronagraphs history teaches that a particular attention must be dedicated to the occulter optimization. The METIS occulting system is of particular interest due to its innovative concept. In order to meet the strict thermal requirements of Solar Orbiter, METIS optical design has been optimized by moving the entrance pupil at the level of the external occulter on the S/C thermal shield, thus reducing the size of the external aperture. The scheme is based on an inverted external-occulter (IEO). The IEO consists of a circular aperture on the Solar Orbiter thermal shield. A spherical mirror rejects back the disk-light through the IEO. A breadboard of the occulting assembly (BOA) has been manufactured in order to perform stray light tests in front of two solar simulators (in Marseille, France and in Torino, Italy). A first measurement campaign has been carried on at the Laboratoire d'Astrophysique de Marseille. In this paper we describe the BOA design, the laboratory set-up and the preliminary results.
JWST Overview
The James Webb Space Telescope: extending the science
Show abstract
The science objectives of the James Webb Space Telescope fall into four themes. The End of the Dark Ages: First Light
and Reionization theme seeks to identify the first luminous sources to form and to determine the ionization history of the
universe. The Assembly of Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars, metals,
morphological structures, and black holes within them evolved from the epoch of reionization to the present. The Birth
of Stars and Protoplanetary Systems theme seeks to unravel the birth and early evolution of stars, from infall onto dust-enshrouded
protostars, to the genesis of planetary systems. The Planetary Systems and the Origins of Life theme seeks to
determine the physical and chemical properties of planetary systems around nearby stars and of our own, and to
investigate the potential for life in those systems. These four science themes were used to establish the design
requirements for the observatory and instrumentation. Since Webb’s capabilities are unique, those science themes will
remain relevant through launch and operations and goals contained within these themes will continue to guide the design
and implementation choices for the mission. More recently, it has also become clear that Webb will make major
contributions to other areas of research, including dark energy, dark matter, exoplanet characterization and Solar System
objects. In this paper, I review the original four science themes and discuss how the scientific output of Webb will
extend to these new areas of research.
Science operations with the James Webb Space Telescope
Jane Rigby,
George Sonneborn,
Joe Pollizzi,
et al.
Show abstract
The James Webb Space Telescope (JWST) will be a powerful space observatory whose four science instruments will
deliver rich imaging and multiplexed spectroscopic datasets to the astronomical and planetary science communities.
The ground segment for JWST, now being designed and built, will carry out JWST's science operations. The ground
segment includes:
software that the scientific community will use to propose and specify new observations;
systems that will schedule science and calibration observations in a way that respects physical and investigator-specified
constraints, while satisfying preferences for efficient observing, low background levels, and distributed
subscription across a year;
the infrastructure to regularly measure and maintain the telescope's wavefront;
orbit determination, ranging, and tracking;
communication via the Deep Space Network to command the observatory and retrieve scientific data;
onboard scripts that execute each observing program in an event-driven fashion, with occasional interruptions for
targets of opportunity or time-critical observations; and
a system that processes and calibrates the data into science-ready products, automatically recalibrates when calibrations
improve, and archives the data for timely access by the principal investigator and later worldwide access by the scientific
community.
This ground system builds on experience from operating the Hubble Space Telescope, while solving challenges that are
unique to JWST. In this paper, we describe the elements of the JWST ground system, how it will work operationally
from the perspective of the observatory itself, and how a typical user will interact with the system to turn their idea into
scientific discovery.
Status of the James Webb Space Telescope Observatory
Show abstract
The James Webb Space Telescope (JWST) is the largest cryogenic, space telescope ever built, and will
address a broad range of scientific goals from first light in the universe and re-ionization, to
characterization of the atmospheres of extrasolar planets. Recently, significant progress has been made in
the construction of the observatory with the completion of all 21 flight mirrors that comprise the
telescope’s optical chain, and the start of flight instrument deliveries to the Goddard Space Flight Center.
In this paper we discuss the design of the observatory, and focus on the recent milestone achievements in
each of the major observatory sub-systems.
James Webb Space Telescope optical telescope element mirror development history and results
Show abstract
In a little under a decade, the James Webb Space Telescope (JWST) program has designed, manufactured,
assembled and tested 21 flight beryllium mirrors for the James Webb Space Telescope Optical Telescope
Element. This paper will summarize the mirror development history starting with the selection of
beryllium as the mirror material and ending with the final test results. It will provide an overview of the
technological roadmap and schedules and the key challenges that were overcome. It will also provide a
summary of the key tests that were performed and the results of these tests.
Observatory alignment of the James Webb Space Telescope
Show abstract
The payload portion of James Web Space Telescope (JWST) consists of a deployable, three mirror anistigmat, telescope
and an Integrated Science Instrument Model (ISIM) that contains the scientific instruments. This paper describes the
overall process and strategy of aligning the Observatory in an efficient manner that reduces risk and strives to be tolerant
of faults in the system. A process has been developed consisting of ground calibration of the instruments and alignment
testing of the fixed optics to ensure that the telescope is alignable in space. The overall architecture of the alignment
process and the processes to safely and efficiently conduct the optical commissioning is described.
JWST Optics/I&T I
Status of the JWST optical telescope element
Show abstract
Significant progress has been made in the development of the Optical Telescope Element (OTE) for the James Webb
Space Telescope (JWST) Observatory. All of the mirror assemblies are complete and through final testing. The
composite Pathfinder Primary Mirror Backplane Support Structure (PMBSS) has been completed and the flight
structure is making significant progress. This paper will discuss the current status of all the OTE components and
the plan forward to completion.
Statistical analysis of the surface figure of the James Webb Space Telescope
Show abstract
The performance of an optical system is best characterized by either the point spread function (PSF) or the optical
transfer function (OTF). However, for system budgeting purposes, it is convenient to use a single scalar metric, or a
combination of a few scalar metrics to track performance. For the James Webb Space Telescope, the Observatory
level requirements were expressed in metrics of Strehl Ratio, and Encircled Energy. These in turn were converted to
the metrics of total rms WFE and rms WFE within spatial frequency domains. The 18 individual mirror segments
for the primary mirror segment assemblies (PMSA), the secondary mirror (SM), tertiary mirror (TM), and Fine
Steering Mirror have all been fabricated. They are polished beryllium mirrors with a protected gold reflective
coating. The statistical analysis of the resulting Surface Figure Error of these mirrors has been analyzed. The
average spatial frequency distribution and the mirror-to-mirror consistency of the spatial frequency distribution are
reported. The results provide insight to system budgeting processes for similar optical systems.
Predicted JWST imaging performance
Show abstract
The James Webb Space Telescope optical telescope element mirror components, 18 individual primary mirror segment
assemblies (PMSA), the secondary mirror (SM), tertiary mirror (TM), and Fine Steering Mirror, have all been fabricated.
The performance of the optical telescope (OTE) based on the as-measured optical components is combined with
alignment tolerances and the on-orbit alignment process to predict the imaging performance of JWST. The best
estimate of the wavefront error, Strehl ratio and Encircled Energy stability is presented.
Wavefront sensing and controls for the James Webb Space Telescope
Show abstract
The James Webb Space Telescope (JWST) is a segmented deployable telescope, utilizing 6 degrees of freedom for
adjustment of the Secondary Mirror (SM) and 7 degrees of freedom for adjustment of each of its 18 segments in the
Primary Mirror (PM). When deployed, the PM segments and the SM will be placed in their correct optical positions to
within a few mm, with accordingly large wavefront errors. The challenge, therefore, is to position each of these optical
elements in order to correct the deployment errors and produce a diffraction-limited telescope, at λ=2μm, across the
entire science field. This paper describes a suite of processes, algorithms, and software that has been developed to
achieve this precise alignment, using images taken from JWST’s science instruments during commissioning. The results
of flight-like end-to-end simulations showing the commissioning process are also presented.
JWST Optics/I&T II
Actuator usage and fault tolerance of the James Webb Space Telescope optical element mirror actuators
Show abstract
The James Webb Space Telescope (JWST) telescope's secondary mirror and eighteen primary mirror segments are
each actively controlled in rigid body position via six hexapod actuators. The mirrors are stowed to the mirror
support structure to survive the launch environment and then must be deployed 12.5 mm to reach the nominally
deployed position before the Wavefront Sensing and Control (WFSandC) alignment and phasing process begins. The
actuation system is electrically, but not mechanically redundant. Therefore, with the large number of hexapod
actuators, the fault tolerance of the OTE architecture and WFSandC alignment process has been carefully considered.
The details of the fault tolerance will be discussed, including motor life budgeting, failure signatures, and motor life.
James Webb Space Telescope optical telescope element mirror coatings
Show abstract
James Webb Space Telescope (JWST) Optical Telescope Element (OTE) mirror coating program has been completed.
The science goals of the JWST mission require a uniform, low stress, durable optical coating with high reflectivity over
the JWST spectral region. The coating has to be environmentally stable, radiation resistant and compatible with the
cryogenic operating environment. The large size, 1.52 m point to point, light weight, beryllium primary mirror (PM)
segments and flawless coating process during the flight mirror coating program that consisted coating of 21 flight
mirrors were among many technical challenges. This paper provides an overview of the JWST telescope mirror coating
program. The paper summarizes the coating development program and performance of the flight mirrors.
The integration and test program of the James Webb Space Telescope
Show abstract
The James Webb Space Telescope (JWST) project has entered into a comprehensive integration and test (I and T) program that over the coming years will assemble and test the various elements of the observatory and verify the readiness of the integrated system for launch. Highlights of the I and T program include a sequence of cryo-vacuum tests of the Integrated Science Instrument Module (ISHvf), to be carried out at NASA's Goddard Space Flight Center (GSFC) and an end-to- end cryo-vacuum optical and thermal test - of unprecedented scale - of the telescope plus instruments at NASA's Johnson Space Center (JSC). The I and T program, as replanned for a 2018 launch readiness date, contains a number of risk-reduction features intended to maximize the prospects for success of the critical tests, leading to reduced cost and schedule risk for those activities. For the JSC test, these include enhancement of the precursor Pathfinder program, the addition of a second cryo-vacuum thermal test of the observatory's Core region, and enhancement of the subsystem level testing program for the cryo-cooler for the Mid-InfraRed Instrument (MlRl). We report here on the I and T program for JWST, focusing on the I and T path for the instruments and telescope, and on the status of the hardware and plans that support it.
JWST's cryogenic position metrology system
Show abstract
The James Webb Space Telescope will undergo a full system test in the cryogenic vacuum chamber A at the Johnson
Spaceflight Center in order to verify the overall performance of the combined telescope and instrument suite. This will
be the largest and most extensive cryogenic test ever undertaken. Early in the test system development, it was
determined that precise position measurements of the overall hardware would enhance the test results. Various concepts
were considered before selecting photogrammetry for this metrology. Photogrammetry has been used in space systems
for decades, however cryogenic use combined with the size and the optical/thermal sensitivity of JWST creates a unique
set of implementation challenges. This paper provides an overview of the JWST photogrammetric system and mitigation
strategies for three key engineering design challenges: 1) the thermal design of the viewing windows to prevent
excessive heat leak and stray light to the test article 2) cost effective motors and mechanisms to provide the angle
diversity required, and 3) camera-flash life and reliability sufficient for inaccessible use during the number and duration
of the cryogenic tests.
Status of the James Webb Space Telescope integrated science instrument module
Show abstract
The Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) is discussed from a
systems perspective with emphasis on development status and advanced technology aspects. The ISIM is one of
three elements that comprise the JWST space vehicle and is the science instrument payload of the JWST. The major
subsystems of this flight element and their build status are described.
JWST Instruments
Science opportunities with the near-IR camera (NIRCam) on the James Webb Space Telescope (JWST)
Show abstract
The Near-Infrared Camera (NIRCam) on the James Webb Space Telescope (JWST) offers revolutionary gains in
sensitivity throughout the 1-5 μm region. NIRCam will enable great advances in all areas of astrophysics, from the
composition of objects in our own Kuiper Belt and the physical properties of planets orbiting nearby stars to the
formation of stars and the detection of the youngest galaxies in the Universe. NIRCam also plays an important role in
initial alignment of JWST and the long term maintenance of its image quality. NIRCam is presently undergoing
instrument Integration and Test in preparation for delivery to the JWST project. Key near-term milestones include the
completion of cryogenic testing of the entire instrument; demonstration of scientific and wavefront sensing performance
requirements; testing of replacement H2RG detectors arrays; and an analysis of coronagraphic performance in light of measured telescope wavefront characteristics. This paper summarizes the performance of NIRCam, the scientific and
education/outreach goals of the science team, and some results of the on-going testing program.
The JWST near-infrared spectrograph NIRSpec: status
Show abstract
The Near-Infrared Spectrograph NIRSpec is one of the four instruments of the James Webb Space Telescope (JWST).
NIRSpec will cover the 0.6-5.0 micron range and will be capable of obtaining spectra of more than 100 objects
simultaneously in its multi-object spectroscopy (MOS) mode. It also features a set of slits and an aperture for high
contrast spectroscopy of individual sources, as well as an integral-field unit (IFU) for 3D spectroscopy. We will first
show how these capabilities are linked to the four main JWST scientific themes. We will then give an overview of the
NIRpec modes and spectral configurations with an emphasis on the layout of the field of view and of the spectra. Last,
we will provide an update on the status of the instrument.
Ambient alignment verification of JWST-MIRI
Show abstract
We report on the alignment verification activities using optical visible techniques, and performed at ambient temperature
before and after environmental and qualification tests, on the Mid InfraRed Instrument (MIRI), one of the scientific
instruments on-board the James Webb Space Telescope (JWST). More specifically, the method developed to measure
some of the instrument key parameters, such as pupil shear and focus offset, is explained in details. We describe the
chosen approach, the associated common hardware, the initial set-up and alignment, then discuss the measurements
themselves and finally the data analysis, before concluding on the successful application of such approach to the optical
characterization of the MIRI flight model.
The JWST Fine Guidance Sensor (FGS) and Near-Infrared Imager and Slitless Spectrograph (NIRISS)
Show abstract
The Fine Guidance Sensor (FGS) is one of the four science instruments on board the James Webb Space Telescope (JWST). FGS features two modules: an infrared camera dedicated to fine guiding of the observatory and a science camera module, the Near-Infrared Imager and Slitless Spectrograph (NIRISS) covering the wavelength range between 0.7 and 5.0 μm with a field of view of 2.2' X 2.2'. NIRISS has four observing modes: 1) broadband imaging featuring seven of the eight NIRCam broadband filters, 2) wide-field slitless spectroscopy at a resolving power of rv150 between 1 and 2.5 μm, 3) single-object cross-dispersed slitless spectroscopy enabling simultaneous wavelength coverage between 0. 7 and 2.5 μm at Rrv660, a mode optimized for transit spectroscopy of relatively
bright (J > 7) stars and, 4) sparse aperture interferometric imaging between 3.8 and 4.8 μm enabling high
contrast ("' 10-4) imaging of M < 8 point sources at angular separations between 70 and 500 milliarcsec. This
paper presents an overview of the FGS/NIRISS design with a focus on the scientific capabilities and performance offered by NIRISS.
Non-redundant Aperture Masking Interferometry (AMI) and segment phasing with JWST-NIRISS
Show abstract
The Aperture Masked Interferometry (AMI) mode on JWST-NIRISS is implemented as a 7-hole, 15% throughput, non-redundant mask (NRM) that operates with 5-8% bandwidth filters at 3.8, 4.3, and 4.8 microns. We present refined estimates of AMI's expected point-source contrast, using realizations of noise matched to JWST pointing requirements, NIRISS detector noise, and Rev-V JWST wavefront error models for the telescope and instrument. We describe our point-source binary data reduction algorithm, which we use as a standardized method to compare different observational strategies. For a 7.5 magnitude star we report a 10-a detection at between
8.7 and 9.2 magnitudes of contrast between 100 mas to 400 mas respectively, using closure phases and squared visibilities in the absence of bad pixels, but with various other noise sources. With 3% of the pixels unusable, the expected contrast drops by about 0.5 magnitudes. AMI should be able to reach targets as bright as M=5. There will be significant overlap between Gemini-GPI and ESO-SPHERE targets and AMI's search space, and a complementarity with NIRCam's coronagraph. We also illustrate synthesis imaging with AMI, demonstrating an imaging dynamic range of 25 at 100 mas scales. We tailor existing radio interferometric methods to retrieve a faint bar across a bright nucleus, and explain the similarities to synthesis imaging at radio wavelengths. Modest contrast observations of dusty accretion flows around AGNs will be feasible for NIRISS AMI. We show our early results of image-plane deconvolution as well. Finally, we report progress on an NRM-inspired approach to mitigate mission-level risk associated with JWST's specialized wavefront sensing hardware. By combining narrow band and medium band Nyquist-sampled images taken with a science camera we can sense JWST primary mirror segment tip-tilt to lOmas, and piston to a few nm. We can sense inter-segment piston errors of up to 5 coherence lengths of the broadest bandpass filter used ( 250-500 0m depending on the filters). Our approach scales well with an increasing number of segments, which makes it relevant for future segmented-primary space missions.
Poster Session: ECHO
The Exoplanet Characterisation Observatory (EChO) payload electronics
Show abstract
The EChO Payload is an integrated spectrometer designed to cover the 0.55-16 μm (11 to 16 μm as a goal) wavelength
band, subdivided into 5 channels from visible to thermal IR with a common set of optics spectrally dividing the field of
view by means of dichroics and a unique electronics interface to the spacecraft, the Data Control Unit (DCU). DCU is
mainly a digital unit with processing capabilities based on a rad-hard space qualified processor running the main
Application SW (the scientific SW) and some programmable logics.
DCU will host the detector’s warm front-end electronics (FEEs) and its main tasks are to implement the payload
instruments commanding, the science and housekeeping (HK) data acquisition, conversion and packetisation, the
onboard spectra pre-processing, and, finally, to provide finely regulated voltage levels to FEEs. Detector’s proximity
cold electronics send analog data and HKs to DCU for digital conversion by sharing a redundant ADC aboard DCU.
Analog HKs are previously multiplexed, elaborated and converted to digital format before sending them to the satellite
platform, via the SpaceWire (SpW) links.
DCU controls the FEEs syncronization (interpreting and routing sync signals and time stamps sent by OBC by means of
SpW Time Codes) and runs the main logics to perform all the required tasks and memory management.
The EChO DCU electronics basically focuses on the data and command flows, the clock/synchronization and power
distribution network and on an overall architecture for a trade-off solution removing or reducing any electronics single-point
failure.
Mechanical and thermal architecture of an integrated payload instrument for the Exoplanet Characterisation Observatory
Show abstract
The Exoplanet Characterisation Observatory (EChO) is a space mission dedicated to undertaking spectroscopy of
transiting exoplanets over the widest wavelength range possible. It is based around a highly stable space platform with a
1.2 m class telescope. The mission is currently being studied by ESA in the context of a medium class mission within the
Cosmic Vision programme for launch post 2020. The payload instrument is required to provide simultaneous coverage
from the visible to the mid-infrared and must be highly stable and effectively operate as a single instrument.
This paper presents the architectural design for the highly interlinked mechanical and thermal aspects of our instrument
design. The instrument will be passively cooled to approximately 40K along with the telescope in order to maintain the
necessary sensitivity and photometric stability out to mid-infrared wavelengths. Furthermore other temperature stages
will be required within the instrument, some of which will implement active temperature control to achieve the necessary
thermal stability. We discuss the major design drivers of this complex system such as the need for multiple detector
system temperatures of approximately 160K, 40K and 7K all operating within the same instrument.
The sizing cases for the cryogenic system will be discussed and the options for providing the cooling of detectors to
approximately 7K will be examined. We discuss the trade-offs that we are undertaking to produce a technically feasible
payload design which will enable EChO’s exciting science.
EChO SWiR: exoplanet atmospheres characterization observatory sort-wave infrared channel of the EChO payload
Show abstract
EChO, a space mission for exoplanets exploration, is considered the next step for planetary atmospheres
characterization. It will be a dedicated observatory to uncover a large selected sample of planets spanning a
wide range of masses (from gas giants to super-Earths) and orbital temperatures (from hot to habitable). All
targets move around stars of spectral types F, G, K, and M. EChO will provide an unprecedented view of the
atmospheres of planets in the solar neighbourhood.
The consortium formed by various institutions of different countries is proposing an integrated
spectrometer payload for EChO covering the wavelength interval 0.4 to 16 µm. This instrument is subdivided
into 4 channels: a visible channel, which includes a fine guidance system (FGS) and a VIS spectrometer, a
near infrared channel (SWiR), a middle infrared channel (MWiR), and a long wave infrared module (LWiR).
In addition, it contains a common set of optics spectrally dividing the wavelength coverage and injecting the
combined light of parent stars and their exoplanets into the different channels. The proposed payload meets all
of the key performance requirements detailed in the ESA call for proposals as well as all scientific goals.
EChO payload will be based on different spectrometers covering the spectral range mentioned above.
Among them, SWiR spectrometer will work from 2.45 microns to 5.45 microns. In this paper, the optical and
mechanical designs of the SWiR channel instrument, including the evolution of the different trades followed
and the current identification of critical points, are reported on.
The visible and near infrared (VNIR) spectrometer of EChO
Show abstract
The Visible and Near Infrared (VNIR) spectrometer of the EChO will cover the spectral range between 0.55 and 2.50 μm. It has to be designed to assure a high efficiency over whole spectral range. It has to be able to observe stars with an apparent magnitude Mv= 9÷12 and able to see contrasts of the order of 10-4÷10-5 in order to measure characteristics of the exoplanets under investigation. VNIR would be a spectrometer in a cross-dispersed configuration by using a combination of a diffraction grating and a prism to spread the light in different wavelengths and in a useful number of orders of diffraction. It will use a Mercury Cadmium Telluride detector to satisfy the requirements of low thermal noise and the EChO system to operate at the working temperature of 40-45K. The instrument will be interfaced to the telescope optics by optical fibers to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench. The preliminary design of the instrument foresees a resolving power of about 330 with an entrance aperture of 2 arcsec.
A detector technology investigation for the Exoplanet Characterisation Observatory (EChO)
Show abstract
The Exoplanet Characterisation Observatory (EChO) is currently being studied by ESA as a medium class mis sion to be launched in the third decade of the new millennium. EChO requires exquisite detector sensitivity and stability under low- background conditions. The EChO longest wavelength instrument covers the very long wave length (VLWIR) spectral band from 10 to 16 µm and HgCdTe (MCT) photoconductors constitute a promising technology. Currently available MCT detectors have been developed for high-background and high-temperature operations and little is known about the performance achievable when the same detectors are operated at cryo genic temperatures, between 77 K and 4 K. Here we report on the optical and dark measurements obtained on VLWIR MCT photoconductors from European manufacturers at cryogenic temperatures.
The study of magnetic activity and exoplanet magnetospheres using EChO VNIR-channel spectropolarimetry
Show abstract
The EChO satellite provides an opportunity to investigate the magnetic stellar activity and the nature of magnetic
interactions of exoplanets with their host stars by using spectropolarimetry from space. These include auroral phenomena
induced by the coupling on the exoplanet, induced flows between the planet and parent star, and a broad range of
signatures of enhanced magneto-hydrodynamic interactions.
A comprehensive view of the structure and evolution of exoplanetary atmospheres requires investigating the escape
mechanisms of their constituent species, including the effect of a planetary magnetosphere. Given the distribution of
masses and orbital parameters among the currently known gas giant exoplanets, the presence of a significant magnetic
field could have some surprising consequences. In analogy with active dynamo-generated fields in close binary star
systems, such as the RS CVn stars, a planetary field could link to that of the parent star, producing a strongly dissipative
torque and magnetically and tidally locking the planet to its central star. Additionally, the study of stellar magnetism aids
understanding of the coronal and chromospheric activity that affects the evolution of the planetary atmospheres.
Poster Session: EUCLID
An end-to-end approach to the EUCLID NISP on-board pre-processing operations: tests and latest results
Show abstract
NISP is the near IR spectrophotometer instrument part of the Cosmic Vision Euclid mission. In this paper we describe an
end-to-end simulation scheme developed in the framework of the NISP design study to cover the expected focal-plane
on-board pre-processing operations. Non-destructive detector readouts are simulated for a number of different readout
strategies, taking into account scientific and calibration observations; resulting frames are passed through a series of
steps emulating the foreseen on-board pipeline, then compressed to give the final result. In order to verify final frame
quality and resulting computational and memory load, we tested this architecture on a number of hardware platforms
similar to those possible for the final NISP computing unit. Here we give the results of the latest tests. This paper mainly
reports the technical status at the end of the Definition Phase and it is presented on behalf of the Euclid Consortium.
The on-board electronics for the near infrared spectrograph and photometer (NISP) of the EUCLID Mission
Show abstract
The Near Infrared Spectrograph and Photometer (NISP) is one of the instruments on board the EUCLID mission.
The focal plane array (FPA) consists of 16 HAWAII-2RG HgCdTe detectors from Teledyne Imaging Scientific
(TIS), for NIR imaging in three bands (Y, J, H) and slitless spectroscopy in the range 0.9−2µm. Low total noise
measurements (i.e. total noise < 8 electrons) are achieved by operating the detectors in multiple non-destructive
readout mode for the implementation of both the Fowler and Up-The-Ramp (UTR) sampling, which also enables
the detection and removal of cosmic ray events. The large area of the NISP FPA and the limited satellite telemetry
available impose to perform the required data processing on board, during the observations. This requires a well
optimized on-board data processing pipeline, and high-performance control electronics, suited to cope with the
time constraints of the NISP acquisition sequences. This paper describes the architecture of the NISP on-board
electronics, which take charge of several tasks, including the driving of each individual HAWAII-2RG detectors
through their SIDECAR ASICs, the data processing, inclusive of compression and storage, and the instrument
control tasks. We describe the implementation of the processing power needed for the demanding on-board data
reduction. We also describe the basic operational modes that will be managed by the system during the mission,
along with data flow and the Telemetry/TeleCommands flow. This paper reports the NISP on-board electronics
architecture status at the end of the Phase B1, and it is presented on behalf of the Euclid Consortium.
The command and data processing unit of the Euclid Visible Imager: impact of the data compression needs on the unit design
Show abstract
The Command and Data Processing Unit (CDPU) of the Euclid Visible Imager is one of the two warm electronics units
of the instrument. It implements on one side the digital interface to the satellite, for telecommands acquisition and
telemetry downloading, and on the other side the interface to the focal plane CCDs readout electronics, for science data
acquisition and compression. The CDPU main functionalities include the instrument commanding, control and health
monitoring. The baseline unit architecture is presented, reporting the results of the phase B1 study and of the trade-off
activity carried out to check the performances of the SW implementation of two different lossless compression
algorithms on the baseline target processor (LEON3-FT) and on a HW compressor.
Euclid NISP thermal control design
Show abstract
In this paper we describe the thermal architecture of the Near Infrared Spectro-Photometer (NISP) on board the Euclid
ESA mission.
The instrument thermal design is based on the combination of two passive radiators coupled to cold space that, exploiting
the beneficial conditions of the L2 thermal environment, provide the temperature references for the main sub-systems.
One radiator serves as a 135K heat sink for the opto-mechanical structure and for the front-end cold electronics, while
working as an interception stage for the conductive parasitic heat leaks through struts and harness. The second, colder,
radiator provides a 95K reference for the instrument detectors. The thermal configuration has to ensure the units optimal
operating temperature needed to maximize instrument performance, adopting solutions consistent with the mechanical
specifications. At the same time the design has to be compliant with the stringent requirements on thermal stability of the
optical and detector units. The periodical perturbation of filter and grism wheel mechanisms together with orbital
variations and active loads instabilities make the temperature control one of the most critical issues of the whole design.
We report here the general thermal architecture at the end of the Definition Phase, together with the first analysis results
and preliminary performance predictions in terms of steady state and transient behavior. This paper is presented on
behalf of the Euclid Consortium.
Design concept of the electrical ground support equipment for the AIV and calibration of the Euclid NISP instrument
Show abstract
The Near Infrared Spectro-Photometer (NISP) on board the Euclid ESA mission will be developed and tested at various
levels of integration using various test equipment which shall be designed and procured through a collaborative and
coordinated effort.
In this paper we describe the Electrical Ground Support Equipment (EGSE) which shall be required to support the
assembly, integration, verification and testing (AIV/AIT) and calibration activities at instrument level before delivery to
ESA, and at satellite level, when the NISP instrument is mounted on the spacecraft.
We present the EGSE conceptual design as defined in order to be compliant with the AIV/AIT and calibration
requirements. The proposed concept is aimed at maximizing the re-use in the EGSE configuration of the Test Equipment
developed for subsystem level activities, as well as, at allowing a smooth transition from instrument level to satellite
level, and, possibly, at Ground Segment level.
This paper mainly reports the technical status at the end of the Definition phase and it is presented on behalf of the
Euclid Consortium.
Poster Session: Hubble and SPITZER
Keeping the Hubble Space Telescope in focus
Show abstract
The Hubble Space Telescope is a Ritchie-Chrétien optical design with a main primary concave mirror followed by a
convex secondary. The focus is determined by the position of each of these two mirrors. The truss containing them is
made of graphite epoxy which has very low thermal expansion. Nevertheless, temperature variations do cause the mirror
separation to vary by several microns within an orbit. Additionally, outgassing of water vapor causes a long-term
shrinkage which soon after launch in 1990 varied by more than 2 microns per month. This necessitated adjusting the
position of the secondary mirror every few months. Currently this rate is greatly reduced and adjustments are needed less
than once per year.
The focus is monitored monthly to continually assess the need for such adjustments. The measurements have been used
to develop models to predict the focus at times between measurements to assist in the analysis of observations. Detailed
focus knowledge is of value in photometry, coronagraphy and image deconvolution. The various focus models that have
been applied so far are described with an evaluation of their performance. Continuing attempts to refine the model will
be discussed.
Modifications to the warm Spitzer data reduction pipeline
Show abstract
The Spitzer Space Telescope Infrared Array Camera (IRAC) basic calibrated data reduction pipeline is designed to take
a single raw frame from a single IRAC detector and produce a flux-calibrated image that has had all well-understood
instrumental signatures removed. We discuss several modifications to the pipeline developed in the last two years in
response to the Spitzer warm mission. Due to the different instrument characteristics in the warm mission, we have
significantly changed pipeline procedures for masking residual images and mitigating column pulldown. In addition, the
muxbleed correction was turned off, because it is not present in the warm data. Parameters relevant to linearity
correction, bad pixels, and the photometric calibration have been updated and are continually monitored.
The IRAC point response function in the warm Spitzer mission
Show abstract
The Infrared Array Camera (IRAC) is now the only science instrument in operation on the Spitzer Space Telescope. The
3.6 and 4.5 µm channels are temperature-stabilized at ~28.7K, and the sensitivity of IRAC is nearly identical to what it
was in the cryogenic mission. The instrument point response function (PRF) is a set of values from which one can
determine the point spread function (PSF) for a source at any position in the field, and is dependent on the optical
characteristics of the telescope and instrument as well as the detector sampling and pixel response. These data are
necessary when performing PSF-fitting photometry of sources, for deconvolving an IRAC image, subtracting out a
bright source in a field, or for estimating the flux of a source that saturates the detector. Since the telescope and
instrument are operating at a higher temperature in the post-cryogenic mission, we re-derive the PRFs for IRAC from
measurements obtained after the warm mission temperature set point and detector biases were finalized and compare
them to the 3.6 and 4.5 µm PRFs determined during the cryogenic mission to assess any changes.
Poster Session: JWST
Optical transmission for the James Webb Space Telescope
Show abstract
The fabrication and coating of the mirrors for the James Webb Space Telescope has been completed. The
spectral reflectivity of the protected gold coated beryllium mirrors has been measured. The predicted
end-of-life transmission through the telescope builds from these values. The additional phenomena that
have been analyzed are contamination effects and effects of the environment for the JWST operation
about the Earth-Sun L2 Lagrange libration point. The L2 environment analysis has been based on
radiation testing of mirror samples and hypervelocity testing to assess the micrometeoroid impact effects.
The mirror showed no change in reflectance over the VIS-SWIR wavelengths after exposure to 6-9 Grad
(Si) that simulated 6 years orbiting the L2 Lagrange point. The effects of hypervelocity particle impacts
on the mirrors from test data has been extrapolated to the to the anticipated flux characteristics for
micrometeoroids at the L2 environment. The results show that the micrometeoroid effects are orders of
magnitude below the particulate contamination effects. The final end-of-life transmission for the mirrors
including all of these phenomena will meet the performance requirements for JWST.
James Webb Space Telescope stray light performance status update
Show abstract
The James Webb Space Telescope (JWST) is a large space based astronomical telescope that will operate at
cryogenic temperatures. The architecture has the telescope exposed to space, with a large sun shield providing
thermal isolation and protection from direct illumination from the sun. The instruments will have the capability to
observe over a spectral range from 0.6 µm to 28 µm wavelengths. The following paper will present updated stray
light analysis results characterizing the stray light getting to the instrument focal planes from the full galactic sky,
zodiacal background, bright objects near the line of sight, and scattered earth and moon shine. Included is a
discussion of internal alignments of pupils at relevant interface planes to stray light. The amount of self-generated
infrared background from the Observatory that reaches the instrument focal planes will be presented including the
tolerance to the alignment of the edges of the sun shield membranes relative to each other and the telescope.
Multi-field alignment of the James Webb Space Telescope
Show abstract
When the secondary mirror (SM) of a Three-Mirror Anastigmat (TMA) telescope is misaligned with respect to the
primary mirror (PM), optical wavefront errors are created. In general, the errors take the form of a dominant coma term,
common to all field points, in addition to astigmatism and power terms which vary with field position. The magnitude of
the field dependent wavefront is usually only a few percent of that of the common coma term, depending on the size of
the field of view being considered. The architecture of the James Webb Space Telescope (JWST), however, presents a
unique optical problem in that the common term created by misplacement of the SM is compensated by adjustment of
the PM segments. As such, the residual field dependent terms become dominant and can be sensed at multiple field
points using phase retrieval techniques. In this paper, we present a linear set of equations that describe the multi-field
(MF) wavefront errors resulting from a misaligned SM. It is shown that inverting these equations yields corrections for
the SM alignment that can independently control the field-dependent astigmatism and the focal-plane tilt. Computer
simulations illustrating the correction are presented.
Simulating point spread functions for the James Webb Space Telescope with WebbPSF
Show abstract
Experience with the Hubble Space Telescope has shown that accurate models of optical performance are extremely
desirable to astronomers, both for assessing feasibility and planning scientific observations, and for data analyses
such as point-spread-function (PSF)-fitting photometry and astrometry, deconvolution, and PSF subtraction.
Compared to previous space observatories, the temporal variability and active control of the James Webb Space
Telescope (JWST) pose a significantly greater challenge for accurate modeling. We describe here some initial
steps toward meeting the community's need for such PSF simulations. A software package called WebbPSF
now provides the capability for simulating PSFs for JWST's instruments in all imaging modes, including direct
imaging, coronagraphy, and non-redundant aperture masking. WebbPSF is intended to provide model PSFs
suitable for planning observations and creating mock science data, via a straightforward interface accessible
to any astronomer; as such it is complementary to the sophisticated but complex-to-use modeling tools used
primarily by optical designers. WebbPSF is implemented using a new exible and extensible optical propagation
library in the Python programming language. While the initial version uses static precomputed wavefront
simulations, over time this system is evolving to include both spatial and temporal variation in PSFs, building
on existing modeling efforts within the JWST program. Our long-term goal is to provide a general-purpose PSF
modeling capability akin to Hubble's Tiny Tim software, and of sufficient accuracy to be useful to the community.
The Near Infrared Spectrograph (NIRSpec) on-ground calibration campaign
Stephan M. Birkmann,
Pierre Ferruit,
Torsten Böker,
et al.
Show abstract
The Near Infrared Spectrograph (NIRSpec) is one of four science instruments aboard the James Webb Space
Telescope (JWST) scheduled for launch in 2018. NIRSpec is sensitive in the wavelength range from ~0.6 to 5.0
micron and will be capable of obtaining spectra from more than a 100 objects simultaneously by means of a
programmable micro shutter array. It will also provide an integral eld unit for 3D spectroscopy and xed slits
for high contrast spectroscopy of individual sources and planet transit observations. We present results obtained
during the rst cryogenic instrument testing in early 2011, demonstrating the excellent optical performance of
the instrument. We also describe the planning of NIRSpecs forthcoming second calibration campaign scheduled
for early 2013.
The spectro-photometric calibration of the JWST NIRSpec instrument
T. Böker,
S. Birkmann,
G. de Marchi,
et al.
Show abstract
NIRSpec is the main near-infrared spectrograph on board the James Webb Space Telescope, offering multi-object
capabilities as well as an integral field unit and a number of fixed slits for studies of individual objects. In this paper, we
describe the unique challenges in calibrating this complex instrument, and the approach taken to deal with them, both in
terms of operational procedures and via automated processing of NIRSpec data. We provide a high-level description of
the sequence of processing steps required for NIRSpec science data, and the necessary on-ground calibration files. We
focus our discussion on the case of a typical multi-object observation with the MSA, in which adjacent micro-shutters
are used to sample the science object and the sky background in an alternating way. This dithering strategy is particularly
well suited for faint targets, but its guiding principles also apply to other NIRSpec modes.
The accuracy of the NIRSpec grating wheel position sensors
Guido De Marchi,
Stephan M. Birkmann,
Torsten Böker,
et al.
Show abstract
We present a detailed analysis of measurements collected during the first ground-based cryogenic calibration campaign
of NIRSpec, the Near-Infrared Spectrograph for the James Webb Space Telescope (JWST). In this paper we concentrate
on the performances of the NIRSpec grating wheel, showing that the magneto-resistive position sensors installed on the
wheel provide very accurate information on the position of the wheel itself, thereby enabling an efficient acquisition of
the science targets and a very accurate extraction and calibration of their spectra.
James Webb Space Telescope first light boresight to spacecraft alignment determination
Show abstract
The James Webb Space Telescope is a large deployable cryogenic space telescope that is pointed on the sky by
control of the attitude of the integrated spacecraft and telescope. The primary mirror has 18 hexagonal Primary
Mirror Segment Assemblies (PMSA) that are deployed; 3 on each of two deployable wings, and 12 on a fixed
central section of the Primary Mirror Backplane Support Structure. The Secondary Mirror (SM) is deployed from
the Secondary Support Structure that folds out from the backplane, and the complete Telescope and Integrated
Science Instrument Module are deployed in extension from the spacecraft. The resulting tolerances will result in a
"first light" image that has a spread array of 18 individual images for each point source located within the field of
view. The initial attitude of the spacecraft will be adjusted to point the telescope to a desired star field for the initial
WFSC commissioning process. The deployment tolerances will result in the telescope field of view being offset
from the desired location. By use of a sequence of pointings, a mosaic "first light" image that includes the
multiplicity of the 18 misaligned segment images may be created that will allow the calibration of the offset between
the telescope boresight and the spacecraft attitude control system, allowing subsequent pointing to be done
accurately to a fraction of the field of view of the instruments using spacecraft attitude control.
Global alignment optimization strategies, procedures, and tools for the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM)
Show abstract
During cryogenic vacuum testing of the James Webb Space Telescope (JWST) Integrated Science Instrument Module
(ISIM), the global alignment of the ISIM with respect to the designed interface of the JWST optical telescope element
(OTE) will be measured through a series of optical characterization tests. These tests will determine the locations and
orientations of the JWST science instrument projected focal surfaces and entrance pupils with respect to their
corresponding OTE optical interfaces. Thermal, finite element and optical modeling will then be used to predict the on-orbit
optical performance of the observatory. If any optical performance non-compliances are identified, the ISIM will
be adjusted to improve its performance. If this becomes necessary, ISIM has a variety of adjustments that can be made.
The lengths of the six kinematic mount struts that attach the ISIM to the OTE can be modified and five science
instrument focus positions and two pupil positions can be individually adjusted as well. In order to understand how to
manipulate the ISIM’s degrees of freedom properly and to prepare for the ISIM flight model testing, we have completed
a series of optical-mechanical analyses to develop and identify the best approaches for bringing a non-compliant ISIM
Element back into compliance. During this work several unknown misalignment scenarios were produced and the
simulated optical performance metrics were input into various mathematical modeling and optimization tools to
determine how the ISIM degrees of freedom should be adjusted to provide the best overall optical performance.
Measuring segmented primary mirror WFE in the presence of vibration and thermal drift on the light-weighted JWST
Show abstract
The light-weighted design of the Optical Telescope Element (OTE) of the James Webb Telescope (JWST) leads to
additional sensitivity to vibration from the ground – an important consideration to the measurement uncertainty of the
wavefront error (WFE) in the primary mirror. Furthermore, segmentation of the primary mirror leads to rigid-body
movements of segment areas in the WFE. The ground vibrations are minimized with modifications to the test facility,
and by the architecture of the equipment supporting the load. Additional special test equipment (including strategically
placed isolators, tunable mass dampers, and cryogenic magnetic dampers) mitigates the vibration and the response
sensitivity before reaching the telescope. A multi-wavelength interferometer is designed and operated to accommodate
the predicted residual vibration. Thermal drift also adds to the measurement variation. Test results of test equipment
components, measurement theory, and finite element analysis combine to predict the test uncertainty in the future
measurement of the primary mirror. The vibration input to the finite element model comes from accelerometer
measurements of the facility with the environmental control pumps operating. One of the isolators have been built and
tested to validate the dynamic performance. A preliminary model of the load support equipment and the OTE with the
Integrated Science Instrument Module (ISIM) is complete. The performance of the add-on dampers have been
established in previous applications. And operation of the multi-wavelength interferometer was demonstrated on a
scaled hardware version of the JWST in an environment with vibration and thermal drift.
Cryogenic performance test results for the flight model JWST fine guidance sensor
Show abstract
The flight model Fine Guidance Sensor (FGS) on the James Webb Space Telescope (JWST) has successfully completed
its performance verification tests. The FGS cryogenic test is described along with some of the key guider performance
results which have been obtained. In particular we describe the noise equivalent angle (NEA) performance as a function
of guide star magnitude for the guider tracking mode. Tracking mode must be able to follow a guide star moving across
the field of view of either guider, primarily to allow the Observatory line of sight to settle in advance of the fine
guidance mode. FGS tracking mode will also be used for JWST’s moving target observing mode. The track testing
made use of the two movable sources within our JWST telescope simulator. The NEA of the FGS-Guiders will in part
determine the ultimate image quality of the JWST Observatory.
Space environment challenges with the tunable Fabry-Perot etalon for the JWST fine guidance sensor
Show abstract
The Fine Guidance Sensor (FGS) on the James Webb Space Telescope (JWST) has a science observing capability that
was to be provided by a tunable Fabry-Pérot etalon incorporating dielectric coated etalon plates with a small vacuum gap
and piezoelectric actuators (PZTs). The JWST etalon was more challenging than our existing ground-based operational
systems due to the low-order gap, the extremely wide waveband and the environmental specifications. Difficulties were
encountered in providing the required performance due to variability in the mechanical gap after exposure to the
vibration, shock and cryogenic cycling environments required for the JWST mission. The risks associated with
operating the flight model etalon in the space environment, along with changes in scientific priorities, resulted in the
etalon being replaced by the grism-based Near-Infrared Imager and Slitless Spectrograph (NIRISS). We describe here
the performance of the etalon system and the unresolved risks that contributed to the decision to change the flight
instrument.
Poster Session: SPICA
The focal plane camera for fine guiding and NIR survey on SPICA
Show abstract
The FPC (Fine-guiding and astroPhysics Camera) consists of two NIR (Near Infrared) cameras as focal plane
instruments of the SPICA (Space Infrared Telescope for Cosmology and Astrophysics). The FPC-G (FPC-Guidance) is
for fine guiding with an accuracy of less than 0.036" at 0.5 Hz, and the FPC-S (FPC-Science) is for a back-up of the
FPC-G as well as for scientific observations with 10 filters - including 3 LVFs (Linear Variable Filter) - in NIR (0.8 -
5.2µm) imaging and spectroscopy. As one of the international consortium member of the SPICA project, KASI (Korea
Astronomy and Space science Institute) is leading the conceptual design and the scientific cases of the FPC with
Korea/Japan participants.
High-resolution and high-precision color-differential astrometry for direct spectroscopy of extrasolar planets onboard SPICA: science and validation experiment
Show abstract
We describe the principles and potential of Color-Differential Astrometry (CDA), a high-resolution technique easily
implementable on the Science Coronographic Instrument (SCI) of the SPICA satellite, and aimed here at the direct
detection and spectroscopy of giant Extrasolar Planets (ESP). By measuring the photocentre of the source diffraction
pattern relatively between dispersed spectral channels, CDA gives access to flux ratio and angular information well
beyond the telescope resolution limit. Applied to known ESPs, it can yield the inclination (thus the mass) and spectrum
of the planet. Our estimates show that low-resolution spectroscopy of Jupiter-radius ESP can be measured within a few
hours for planets at orbital distances ranging from 0.05 AU to a few AUs, thus complementing the detection range
expected using the coronographic measurements. More generally, it may also apply to any unresolved source with some
wavelength-dependent asymmetry.
In addition to the ESP cases considered for the scientific signal and to their associated fundamental noises, we also
present the instrumental effects and a dedicated optical testbench. The combined effects of several instrumental noise
sources can be introduced into our numerical model (pointing errors, beam tip-tilt, optical aberations, variations of the
detector gain table), and then confronted to measurements from the experimental testbench.
SPICA/SAFARI Fourier transform spectrometer mechanism evolutionary design
Show abstract
TNO, together with its partners, have designed a cryogenic scanning mechanism for use in the SAFARI1 Fourier
Transform Spectrometer (FTS) on board of the SPICA mission. SPICA is one of the M-class missions competing to be
launched in ESA's Cosmic Vision Programme2 in 2022. JAXA3 leads the development of the SPICA satellite and SRON
is the prime investigator of the Safari instrument.
The FTS scanning mechanism (FTSM) has to meet a 35 mm stroke requirement with an Optical Path Difference
resolution of less then 15 nm and must fit in a small volume. It consists of two back-to-back roof-top mirrors mounted on
a small carriage, which is moved using a magnetic bearing linear guiding system in combination with a magnetic linear
motor serving as the OPD actuator. The FTSM will be used at cryogenic temperatures of 4 Kelvin inducing challenging
requirements on the thermal power dissipation and heat leak.
The magnetic bearing enables movements over a scanning stroke of 35.5 mm in a small volume. It supports the optics in
a free-floating way with no friction, or other non-linearities, with sub-nanometer accuracy. This solution is based on the
design of the breadboard ODL (Optical Delay Line) developed for the ESA Darwin mission4 and the MABE mechanism
developed by Micromega Dynamics.
During the last couple of years the initial design of the SAFARI instrument, as described in an earlier SPIE 2010 paper5,
was adapted by the SAFARI team in an evolutionary way to meet the changing requirements of the SPICA payload
module. This presentation will focus on the evolution of the FTSM to meet these changing requirements. This work is
supported by the Netherlands Space Office (NSO).
Recent progress in the development of mid-infrared medium resolution spectrometer (MRS) installed in SPICA/MCS
Show abstract
Mid-infrared Medium Resolution Spectrometer (MRS) is one of the key spectroscopic modules of Mid-
Infrared Camera and Spectrometers (MCS) that will be onboard SPICA. MRS is an Echelle Grating
spectrometer designed to observe a number of fine structure lines of ions and atoms, molecular lines, and
band features stemming from solid particles and dust grains of the interstellar and circumstellar
medium in the mid-infrared wavelength range. MRS consists of two channels; the shorter wavelength
channel (MRS-S) covers the spectral range from 12.2 to 23.0 micron with a spectral resolution power of
R~1900-3000 and the longer wavelength channel (MRS-L) covers from 23.0 to 37.5 micron with
R~1100-1500 on the basis of the latest results of the optical design. The distinctive functions of the
MRS are (1) a dichroic beam splitter equipped in the fore-optics, by which the same field of view is
shared between the two channels, and (2) the small format image slicer as the integral field unit
installed in each channel. These functions enable us to collect continuous 12-38 micron spectra of both
the point-like and diffuse sources reliably with a single exposure pointed observation. In this paper, the
specifications and the expected performance of the MRS are summarized on the basis of the latest
results of the optical design. The latest progress in the development of the key technological elements,
such as the Dichroic Beam Splitter and the Small Format Monolithic Slice Mirrors, are also reported.
Experimental and numerical study of stitching interferometry for the optical testing of the SPICA Telescope
Show abstract
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a Japan-led infrared astronomical satellite project
with a 3.2-m lightweight cryogenic telescope. The SPICA telescope has stringent requirements such as that for the
imaging performance to be diffraction-limited at the shortest core wavelength of 5 microns at the operating temperature
of 6 K. The design of the telescope system has been studied by the Europe-Japan telescope working group led by ESA
with the European industries, the results of which will be presented in other papers. We here present our recent optical
testing activities in Japan for the SPICA telescope, focusing on the experimental and numerical studies of stitching
interferometry. The full pupil of the SPICA telescope will be covered by a sub-pupil array consisting of small
autocollimating flat mirrors (ACFs), which are rotated with respect to the optical axis of the telescope. For preliminary
stitching experiments, we have fabricated an 800-mm lightweight telescope all made of the C/SiC called HBCesic, which
is a candidate mirror material for the SPICA telescope, and started optical testing with 900-mm and 300-mm ACFs at an
ambient temperature. ACFs can suffer significant surface deformation in testing a telescope at cryogenic temperatures,
which is difficult to be measured directly. We therefore investigate the effects of the surface figure errors of the ACFs on
stitching results by numerical simulation.
Cooled scientific instrument assembly onboard SPICA
Show abstract
The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) is a 3.2m cooled (below 6K) telescope
mission which covers mid- and far-IR waveband with unprecedented sensitivity. An overview of recent design
updates of the Scientific Instrument Assembly (SIA), composed of the telescope assembly and the instrument
optical bench equipped with Focal Plane Instruments (FPIs) are presented. The FPI international science and
engineering review is on-going to determine the FPI suite onboard SPICA: at present the mandatory instruments
and functions to perform the unique science objectives of the SPICA mission are now consolidated. The final
decision on the composition of the FPI suite is expected in early 2013. Through the activities in the current pre-project
phase, several key technical issues which impact directly on the instruments’ performances and the science
requirements and the observing efficiency have been identified, and extensive works are underway both at
instrument and spacecraft level to resolve these issues and to enable the confirmation of the SPICA FPI suite.
Detector systems for the mid-infrared camera and spectrometer on board SPICA
Show abstract
Mid-infrared Camera and Spectrometer (MCS) is one of focal plane instruments for SPICA (Space Infrared
Telescope for Cosmology and Astrophysics), which have 3 m class 6 K cooled telescope. MCS will provide wide
field imaging and low-, medium-, and high-resolution spectroscopic observing capabilities with 7 detectors in the
wavelength range from 5 to 38 micron. Large format array detectors are required in order to realize wide field of
view in imaging and wide spectral coverage in spectroscopy. We are planning to cover the wavelength range of
5-26 micron by Si:As IBC 2K x 2K and 20-38 micron by Si:Sb BIB 1K x 1K. The development status and their
design including the electrical and thermal design are described.
The instrument control unit of SPICA SAFARI: a macro-unit to host all the digital control functionalities of the spectrometer
Show abstract
We present the preliminary design of the Instrument Control Unit (ICU) of the SpicA FAR infrared Instrument
(SAFARI), an imaging Fourier Transform Spectrometer (FTS) designed to give continuous wavelength coverage in both
photometric and spectroscopic modes from around 34 to 210 µm. Due to the stringent requirements in terms of mass and
volume, the overall SAFARI warm electronics will be composed by only two main units: Detector Control Unit and
ICU. ICU is therefore a macro-unit incorporating the four digital sub-units dedicated to the control of the overall
instrument functionalities: the Cooler Control Unit, the Mechanism Control Unit, the Digital processing Unit and the
Power Supply Unit. Both the mechanical solution adopted to host the four sub-units and the internal electrical
architecture are presented as well as the adopted redundancy approach.
Wideband infrared spectrometer for characterization of transiting exoplanets with space telescopes
K. Enya
Show abstract
This paper presents a conceptual design for a spectrometer designed specifically for characterizing transiting exoplanets
with space-borne infrared telescopes. The design adopting cross-dispersion is intended to be simple, compact, highly
stable, and has capability of simultaneous coverage over a wide wavelength region with high throughput. Typical
wavelength coverage and spectral resolving power is 1-13µm with a spectral resolving power of ~ a few hundred,
respectively. The baseline design consists of two detectors, two prisms with a dichroic coating and microstructured
grating surfaces, and three mirrors. Moving parts are not adopted. The effect of defocusing is evaluated for the case of a
simple shift of the detector, and anisotropic defocusing to maintain the spectral resolving power. Variations in the design
and its application to planned missions are also discussed.
Poster Session: Missions/Concepts
Spectroscopy of exoplanet atmospheres with the FINESSE Explorer mission
Show abstract
FINESSE (Fast INfrared Exoplanet Spectroscopic Survey Explorer) will provide uniquely detailed information on the
growing number of newly discovered planets by characterizing their atmospheric composition and temperature structure.
This NASA Explorer mission, selected for a competitive Phase A study, is unique in its breath and scope thanks to broad
instantaneous spectroscopy from the optical to the mid-IR (0.7 – 5 micron), with a survey of exoplanets measured in a
consistent, uniform way. For 200 transiting exoplanets ranging from Terrestrial to Jovians, FINESSE will measure the
chemical composition and temperature structure of their atmospheres and trace changes over time with exoplanet
longitude. The mission will do so by measuring the spectroscopic time series for a primary and secondary eclipse over
the exoplanet orbital phase curve. With spectrophotometric precision being a key enabling aspect for combined light
exoplanet characterization, FINESSE is designed to produce spectrophotometric precision of better than 100 parts-per-million
per spectral channel without the need for decorrelation. The exceptional stability of FINESSE will even allow
the mission to characterize non-transiting planets, potentially as part of FINESSE’s Participating Scientist Program. In
this paper, we discuss the flow down from the target availability to observations and scheduling to the analysis and
calibration of the data and how it enables FINESSE to be the mission that will truly expand the new field of comparative
exoplanetology.
The GAIA photometric data processing
Show abstract
Gaia is an ESA mission which will measure the positions, distances, space motions, and many physical characteristics
for one billion stars in our Galaxy and beyond. The satellite will have three instruments on board: the
Astrometric Field for the astrometry; the Blue and Red Photometers for the low-resolution spectroscopy and
the Radial Velocity Spectrometer which will allow measuring radial velocities. This paper will give an overview
of the processing of the dispersed images for BP and RP: the data will be corrected for CCD related effects in
the pre-processing, where also the sky background and the flux contamination from neighbouring sources will be
removed; the data will be then internally calibrated to the same "mean instrument" and externally calibrated
to obtain spectrum and flux in physical units, which will be stored in the final catalogue.
High-precision astrometry laboratory demonstration for exoplanet detection using a diffractive pupil telescope
Show abstract
Detection of earth-size exoplanets using the astrometric signal of the host star requires sub microarcsecond measurement
precision. One major challenge in achieving this precision using a medium-size (<2-m) space telescope is the calibration
of dynamic distortions. The researchers propose a diffractive pupil technique that uses an array of approximately 5um
dots on the primary mirror that generate polychromatic diffraction spikes in the focal plane. The diffraction spikes
encode optical distortions in the optical system and may be used to calibrate astrometric measurements. This concept can
be used simultaneously with coronagraphy for exhaustive characterization of exoplanets (mass, spectra, orbit). At the
University of Arizona, a high precision astrometry laboratory was developed to demonstrate the capabilities of this
diffractive pupil concept. The researchers aim to demonstrate that the diffractive pupil can improve current limiting
factors of astrometric accuracy. This paper describes this laboratory and the results showing that this technique can
effectively calibrate dynamic distortions.
Supplementary information on the near-infrared spectroscopic data of the infrared camera (IRC) onboard AKARI
Show abstract
We have investigated the on-orbit properties of the spectroscopic data taken with NIR channel of the
Infrared Camera (IRC) onboard AKARI during the phases 1, 2 and 3. We have determined the boundary
shape of the aperture mask of NIR channel by using the spectroscopic data of uniform zodiacal
background emission. The information on the aperture mask shape is indispensable in modeling and
subtracting the spectroscopic background patterns made by the diffuse background emission such as
zodiacal emission and the Galactic cirrus emission. We also have examined the wavelength dependency
on the profile of the point spread function and its effect on the spectroscopic data. The obtained
information is useful, for example, in reducing the spectroscopic data of a point source badly affected by
bad pixels and in decomposing the overlapping spectra of sources that are aligned in the dispersion
direction with a small offset the cross dispersion direction. In this paper, we summarize the
supplementary knowledge that will be useful for the advanced data reduction procedures of NIR
spectroscopic datasets.
Herschel-SPIRE satellite instrument: configurable on-board software for autonomous and real time operation
Show abstract
The Herschel SPIRE On-Board Software (OBS) is presented. This real time operational software controls the scientific
data transmission and keeps a control layer between the SPIRE Mission Timeline (MTL) and the real instruments status.
It embeds a multithreaded engine that interprets control procedures for the detector and mechanism subsystems. An
autonomous monitoring agent keeps control of subsystems status, and takes local decisions based on pre-loaded reaction
maps. The behaviour of low level system functions is configurable remotely via the reactions maps and control
procedures.
ACCESS: design and sub-system performance
Show abstract
Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant
to many astrophysical problems. ACCESS, “Absolute Color Calibration Experiment for Standard Stars”, is a
series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in
the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from
the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration
accuracy of 1% and a spectral resolving power of 500 across the 0.35-1.7µm bandpass.
Nano-JASMINE: cosmic radiation degradation of CCD performance and centroid detection
Show abstract
Nano-JASMINE (NJ) is a very small astrometry satellite project led by the National Astronomical Observatory
of Japan. The satellite is ready for launch, and the launch is currently scheduled for late 2013 or early 2014.
The satellite is equipped with a fully depleted CCD and is expected to perform astrometry observations for stars
brighter than 9 mag in the zw-band (0.6 µm–1.0 µm). Distances of stars located within 100 pc of the Sun can
be determined by using annual parallax measurements. The targeted accuracy for the position determination of
stars brighter than 7.5 mag is 3 mas, which is equivalent to measuring the positions of stars with an accuracy
of less than one five-hundredth of the CCD pixel size. The position measurements of stars are performed by
centroiding the stellar images taken by the CCD that operates in the time and delay integration mode. The
degradation of charge transfer performance due to cosmic radiation damage in orbit is proved experimentally.
A method is then required to compensate for the effects of performance degradation. One of the most effective
ways of achieving this is to simulate observed stellar outputs, including the effect of CCD degradation, and then
formulate our centroiding algorithm and evaluate the accuracies of the measurements. We report here the planned
procedure to simulate the outputs of the NJ observations. We also developed a CCD performance-measuring
system and present preliminary results obtained using the system.
To PLAnetary Transit or not? An extremely large field of view camera with a CaF2 component tested in thermo-vacuum
Show abstract
Because of its nicely chromatic behavior, Calcium Fluoride (CaF2) is a nice choice for an optical designer as it can easily
solve a number of issues, giving the right extra degree of freedom in the optical design tuning. However, switching from
tablet screens to real life, the scarcity of information -and sometimes the bad reputation in term of fragility- about this
material makes an overall test much more than a "display determination" experiment. We describe the extensive tests
performed in ambient temperature and in thermo-vacuum of a prototype, consistent with flight CTEs, of a 200mm class
camera envisaged for the PLATO (PLAnetary Transit and Oscillations of Stars) mission. We show how the CaF2 lens
uneventfully succeeded to all the tests and handling procedures, and discuss the main results of the very intensive test
campaign of the PLATO Telescope Optical Unit prototype.
Habitable planet finder
Show abstract
A notional space telescope configuration is presented that addresses issues of angular resolution, spectral bandwidth and
rejection of host star glare by means of a double dispersion architecture. The telescope resolves angle by wavelength. In
an earlier embodiment for surveys, a primary objective grating telescope architecture was shown to acquire millions of
objects in one observation cycle, one wave length at a time. The proposed HPF can detect exquisite spectral signatures
out of millions of wavelengths in albedos - one exoplanetary system at a time. Like its predecessor, the new HPF
telescope has a ribbon-shaped flat gossamer membrane primary objective that lends itself to space deployment, but the
preferred embodiment uses a holographic optical element rather than a plane grating. The HOE provides an
improvement in efficiency at select wavelength bands. The considerable length of the membrane can be in the 100 meter
class providing angular resolution sufficient to resolve planets in the habitable zone and also spectral resolution
sufficient to earmark habitability. A novel interferometric secondary spectrograph rejects host star glare. However, the
architecture cannot disambiguate multiple stellar sources and may require unprecedented focal lengths in the primary
objective to isolate one system at a time.
NanoSpec: a diffraction limited micro-spectrograph for pico- and nano-satellites
Show abstract
Here we present a novel diffraction limited spectrograph (NanoSpec) designed for integration in the 0.75kg i-INPSIRE satellite at the University of Sydney. NanoSpec is a single-mode fibre fed spectrograph operating very close to the diffraction limit over a wavelength range of 450nm to 700nm. The spectrograph is fed light via a single-mode (and thus diffraction limited) fibre pseudo-slit, allowing an extremely compact spectrograph while maintaining high performance. The current design has two configurations (for two different detectors), both achieving diffraction limited resolving powers (λ/Δλ) of 650 and 1400 respectively. The primary goal of NanoSpec is to demonstrate the potential of the PIMMS (photonic integrated multimode micro-spectrograph) type design for deployment in high altitude and space-based applications. To that end we present the optical design and laboratory based testing in preparation for a high altitude balloon launch and later on the i-INPSIRE satellite.
Space mission Millimetron for terahertz astronomy
Show abstract
We present an overview of the current status of the space mission Millimetron. Millimetron is a large 10-m
cooled space telescope optimized for operation in the submillimeter and far infrared wavelengths. This mission
will be able to contribute to the solution of several key problems in astrophysics, such as study of the formation
and evolution of stars and planets, galaxies, quasars and many others. The telescope will have an unprecedented
sensitivity in the single-dish observation mode and an extremely high spatial resolution as an element of a
ground-space very long baseline interferometry (VLBI) system. The mission will have a cryogenic instruments
and antenna, which will be cooled passively with radiation shields and actively with mechanical coolers. With
this cooling combination the 10-m space telescope may reach a temperature of about 4.5 K. The Millimetron is
proposed as a Russian-led mission with an extensive international consortium in various countries. The mission
launch is planned for 2017.
Optical telescope BIRT in ORIGIN for gamma ray burst observing
Show abstract
The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray
bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer
to the ESA M3 call for proposal. The optical telescope is a 0.7-m F/1 with a very small instrument box containing 3
instruments: a slitless spectrograph with a resolution of 20, a multi-imager giving images of a field in 4 bands
simultaneously, and a cross-dispersed Échelle spectrograph giving a resolution of 1000. The wavelength range is 0.5 μm
to 1.7 μm. All instruments fit together in a box of 80 mm x 80 mm x 200 mm. The low resolution spectrograph uses a
very compact design including a special triplet. It contains only spherical surfaces except for one tilted cylindrical
surface to disperse the light. To reduce the need for a high precision pointing, an Advanced Image Slicer was added in
front of the high resolution spectrograph. This spectrograph uses a simple design with only one mirror for the collimator
and another for the camera. The Imager contains dichroics to separate the bandwidths and glass thicknesses to
compensate the differences in path length. All 3 instruments use the same 2k x 2k detector simultaneously so that
telescope pointing and tip-tilt control of a fold mirror permit to place the gamma ray burst on the desired instrument
without any other mechanism.
CubeSat deformable mirror demonstration
Show abstract
The goal of the CubeSat Deformable Mirror Demonstration (DeMi) is to characterize the performance of a small
deformable mirror over a year in low-Earth orbit. Small form factor deformable mirrors are a key technology needed to
correct optical system aberrations in high contrast, high dynamic range space telescope applications such as space-based
coronagraphic direct imaging of exoplanets. They can also improve distortions and reduce bit error rates for space-based
laser communication systems. While follow-on missions can take advantage of this general 3U CubeSat platform to test
the on-orbit performance of several different types of deformable mirrors, this first design accommodates a 32-actuator
Boston Micromachines MEMS deformable mirror.
Atmospheric characterization of cold exoplanets with a 1.5-m space coronagraph
Show abstract
Several small space coronagraphs have been proposed to characterize cold exoplanets in reflected light. Studies
have mainly focused on technical feasibility because of the huge star/planet
flux ratio to achieve in the close-in
stellar environment (108-1010 at 0.2"). However, the main interest of such instruments, the analysis of planet
properties, has remained highly unexplored so far. We performed numerical simulations to assess the ability
of a small space coronagraph to retrieve spectra of mature Jupiters, Neptunes and super-Earths under realistic
assumptions. We describe our assumptions: exoplanetary atmosphere models, instrument numerical simulation
and observing conditions. Then, we define a criterion and use it to determine the required exposure times to
measure several planet parameters from their spectra (separation, metallicity, cloud and surface coverages) for
particular cases. Finally, we attempt to define a parameter space of the potential targets. In the case of a
solar-type star, we show that a small coronagraph can characterize the spectral properties of a 2-AU Jupiter up
to 10 pc and the cloud and surface coverage of super-Earths in the habitable zone for a few stars within 4-5 pc.
Potentially, SPICES could perform analysis of a hypothetical Earth-size planet around α Cen A and B.
Starshade design driven by stray light from edge scatter
Show abstract
The use of an external occulter, or starshade, has been proposed as one method for the direct detection and spectral
characterization of terrestrial planets around other stars, a key goal identified in ASTRO2010. Because of the
observational geometry, one of the concerns is stray light from the edge of the starshade that is scattered into the line of
sight of the telescope. We have developed a stray light model using physical properties of a realizable starshade edge
geometry and material to calculate the resulting stray light. The background signal due to stray light has been calculated
for the two telescope architectures adopted for study by the Exoplanet Exploration Program Analysis Group (ExoPAG),
a 4 m monolithic and an 8 m segmented mirror design. Using these results, we have developed a set of design
requirements and structure features that will result in a buildable system with stray light levels that meet the overall
system sensitivity requirements.
Poster Session: Solar System
The processing and power unit of the METIS coronagraph aboard the Solar Orbiter space mission
Show abstract
The Multi Element Telescope for Imaging and Spectroscopy (METIS) is the coronagraph selected for the Solar Orbiter
payload, adopted in October 2011 by ESA for the following Implementation Phase. The instrument design has been
conceived by a team composed by several research institutes with the aim to perform both VIS and EUV narrow-band
imaging and spectroscopy of the solar corona. METIS, owing to its multi-wavelength capability, will address some of
the major open issues in understanding the physical processes in the corona and the solar wind origin and properties,
exploiting the unique opportunities offered by the SO mission profile. The METIS Processing and Power Unit (MPPU) is the Instrument's power supply and on-board data handling modular electronics, designed to address all the scientific requirements of the METIS Coronagraph. MPPU manages data and command flows, the timing and power distribution networks and its architecture reflects several trade-off solutions with respect to the allocated resources in order to reduce any possible electronics single-point failure. This paper reports on the selected HW and SW architectures adopted after the Preliminary Design Review (PDR), performed by ESA in early 2012.
Stray light control for asteroid detection at low solar elongation for the NEOSSat micro-satellite telescope
Show abstract
The Near Earth Object Surveillance Satellite (NEOSSat) is a small satellite dedicated to finding near Earth asteroids. Its
surveying strategy consists of imaging areas of the sky to low solar elongation, while in a sun synchronous polar orbit
(dawn-dusk). A high performance baffle will control stray light mainly due to Earth shine. Observation scenarios
require solar shielding down to 45 degree solar elongation over a wide range of ecliptic latitudes. In order to detect the
faintest objects (approx 20th v mag) given a 15 cm telescope and CCD detection system, background from stray light is a
critical operational concern. The required attenuation is in the order of 10-12. The requirement was verified by analyses;
testing was not attempted because the level of attenuation is difficult to measure reliably. We report consistent results of
stray light optical modelling from two independent analyses. Launch is expected for late 2012.
Determination of ghost images for the wide angle camera of the Rosetta ESA mission
Show abstract
Rosetta is a cornerstone mission of the European Space Agency (ESA); it has been launched in March 2004 and it will
reach its primary target, the 67P/Churyumov Gerasimenko comet, in 2014.
One of the Rosetta instruments is the OSIRIS camera system; it is composed of a Wide Angle Camera (WAC) and a
Narrow Angle Camera (NAC). The NAC will observe at high resolution regions on the comet surface, while the WAC,
12°x12° Field of View (FoV), has been mainly designed for observing the weak coma features surrounding the bright
comet nucleus. Being the expected contrast between the gas and dust jets radiance and the nucleus one of the order of
1/1000, a high contrast capability is required for the WAC camera. To meet this requirement, its optical design is off-axis
and unobstructed, and to deeply study gas and dust emissions, the camera is equipped with 14 filters, each with its proper
wavelength selection characteristics, in the range 230-720 nm.
The theoretical achievable contrast capability is limited by multiple ghost images generated by the optical elements in
the focal plane assembly, in fact the incoming beam is partially reflected on the surfaces of the filters, on the detector
radiation protective glass cover and on the CCD detector itself.
Given that the knowledge of ghosts position and intensity is essential for an adequate scientific data reduction, in this
paper an analysis of the ghosts, the solutions adopted to limit image degradation and the impact on the WAC imaging
performance are presented.
SOLAR-T: terahertz photometers to observe solar flare emission on stratospheric balloon flights
Show abstract
A new solar flare spectral component has been found with intensities increasing for larger sub-THz frequencies,
spectrally separated from the well known microwaves component, bringing challenging constraints for interpretation.
Higher THz frequencies observations are needed to understand the nature of the mechanisms occurring in flares. A twofrequency
THz photometer system was developed to observe outside the terrestrial atmosphere on stratospheric balloons
or satellites, or at exceptionally transparent ground stations. 76 mm diameter telescopes were designed to observe the
whole solar disk detecting small relative changes in input temperature caused by flares at localized positions at 3 and 7
THz. Golay cell detectors are preceded by low-pass filters to suppress visible and near IR radiation, band-pass filters,
and choppers. It can detect temperature variations smaller than 1 K with time resolution of a fraction of a second,
corresponding to small burst intensities. The telescopes are being assembled in a thermal controlled box to which a data
conditioning and acquisition unit is coupled. While all observations are stored on board, a telemetry system will forward
solar activity compact data to the ground station. The experiment is planned to fly on board of long-duration
stratospheric balloon flights some time in 2013-2015. One will be coupled to the GRIPS gamma-ray experiment in
cooperation with University of California, Berkeley, USA. One engineering flight will be flown in the USA, and a 2
weeks flight is planned over Antarctica in southern hemisphere summer. Another long duration stratospheric balloon
flight over Russia (one week) is planned in cooperation with the Lebedev Physics Institute, Moscow, in northern
hemisphere summer.
Echoes: a new instrumental concept of spectro-imaging for Jovian seismology
Show abstract
Echoes is a project of a space-borne instrument which has been proposed as part of the JUICE mission which is selected
in the Cosmic Vision program of the European Space Agency (ESA) to perform seismic and dynamics studies
of Jupiter's interior and atmosphere. Based on an original Mach-Zehnder design, the instrument aims to measure Doppler
shifts of solar spectral lines, which are reflected by cloud layers of Jupiter's upper troposphere, coupled with imaging
capabilities. It is specified to detect global oscillations with degree up to l = 50 and amplitude as low as 1 cm/s at the
surface of Jupiter. In order to check the compliance of the instrument, and its capability to operate in representative
environment (TRL5), we build a prototype to perform tests. In this paper, we present the prototype implemented
at Observatoire de la Côte d'Azur in collaboration with Institut d'Astrophysique Spatiale. We describe the design of the
Mach-Zehnder and the procedure of control and adjustment. We present the necessary tests and we show on simulation
that the measurements will provide the required precision. In conclusion, we will explain the perspective for such a new
instrument.
Preliminary internal straylight analysis of the METIS instrument for the Solar Orbiter ESA mission
Show abstract
METIS, the multi element telescope for imaging and spectroscopy, is a solar coronagraph foreseen for the Solar Orbiter
mission. METIS is conceived to observe the solar corona from a near-sun orbit in three different spectral bands: in the
HeII EUV narrow band at 30.4 nm, in the HI UV narrow band at 121.6 nm, and in the visible light band (500 - 650 nm).
The visible light from the corona is ten million times fainter than the light emitted by the solar disk, so a very stringent
light suppression design is needed for the visible channel. METIS adopts an “inverted occulted” configuration, where the
disk light is shielded by an annular shape occulter, after which an annular aspherical mirror M1 collects the signal
coming from the corona. The disk light heading through M1 is back-rejected by a suitable spherical mirror M0.
This paper presents the stray light analysis for this new-concept configuration, performed with a ray tracing simulation,
to insure the opto-mechanical design grants a stray light level below the limit of 10-9 times the coronal signal intensity. A
model of the optics and of the mechanical parts of the telescope has been realized with ASAP (Breault Research TM); by
means of a Montecarlo ray tracing, the effect of stray light on VIS and UVEUV channels has been simulated.
THERMAP: a mid-infrared spectro-imager based on an uncooled micro-bolometer for space missions to small bodies of the solar system
E. Brageot,
O. Groussin,
P. Lamy,
et al.
Show abstract
We report on the feasibility study of a mid-infrared (8-18 µm) spectro-imager called THERMAP, based on an uncooled
micro-bolometer detector array. Due to the recent technological development of these detectors, which have undergone
significant improvements in the last decade, we wanted to test their performances for the Marco Polo R ESA Cosmic
Vision mission. In this study, we demonstrate that the new generation of uncooled micro-bolometer detectors has all the
imaging and spectroscopic capabilities to fulfill the scientific objectives of this mission.
In order to test the imaging capabilities of the detector, we set up an experiment based on a 640x480 ULIS micro-bolometer
array, a germanium objective and a black body. Using the results of this experiment, we show that calibrated
radiometric images can be obtained down to at least 255 K (lower limit of our experiment), and that two calibration
points are sufficient to determine the absolute scene temperature with an accuracy better than 1.5 K. Adding flux
attenuating neutral density mid-infrared filters (transmittance: 50%, 10%, 1%) to our experiment, we were able to
evaluate the spectroscopic performances of the detector. Our results show that we can perform spectroscopic
measurements in the wavelength range 8-16 µm with a spectral resolution of R~40-80 for a scene temperature <300 K,
the typical surface temperature of a Near Earth Asteroid at 1 AU from the Sun.
The mid-infrared spectro-imager THERMAP, based on the above detector, is therefore well suited for the Marco Polo R
mission.
Image stabilisation system of the photospheric and helioseismic imager
Show abstract
The Photospheric and Helioseismic imager (PHI) on board of the ESA mission Solar Orbiter, to be launched in 2017,
will provide measurements with high polarimetric accuracy of the photospheric solar magnetic field at high solar
latitudes. The needed pointing precision requires an image stabilisation (ISS) to compensate for spacecraft jitter. The
image stabilisation system works as a correlation tracker with a high-speed camera and a fast steerable mirror. The optomechanical
and electronic design of the system will be presented.
Poster Session: Technologies
Complex apodization Lyot coronagraphy for the direct imaging of exoplanet systems: design, fabrication, and laboratory demonstration
Show abstract
We review the design, fabrication, performance, and future prospects for a complex apodized Lyot coronagraph for highcontrast
exoplanet imaging and spectroscopy. We present a newly designed circular focal plane mask with an inner
working angle of 2.5 λ/D. Thickness-profiled metallic and dielectric films superimposed on a glass substrate provide
control over both the real and imaginary parts of the coronagraph wavefront. Together with a deformable mirror for
control of wavefront phase, the complex Lyot coronagraph potentially exceeds billion-to-one contrast over dark fields
extending to within angular separations of 2.5 λ/D from the central star, over spectral bandwidths of 20% or more, and
with throughput efficiencies better than 50%.
Our approach is demonstrated with a linear occulting mask, for which we report our best laboratory imaging contrast
achieved to date. Raw image contrasts of 3×10-10 over 2% bandwidths, 6×10-10 over 10% bandwidths, and 2×10-9 over
20% bandwidths are consistently achieved across high contrast fields extending from an inner working angle of 3 λ/D to
a radius of 15 λ/D. Occulter performance is analyzed in light of experiments and optical models, and prospects for
further progress are summarized.
The science capability of the hybrid Lyot coronagraph is compared with requirements for ACCESS, a representative
space coronagraph concept for the direct imaging and spectroscopy of exoplanet systems. This work has been supported
by NASA’s Strategic Astrophysics Technology / Technology Demonstrations for Exoplanet Missions (SAT/TDEM)
program.
Kalman filter estimation for focal plane wavefront correction
Show abstract
Space-based coronagraphs for future earth-like planet detection will require focal plane wavefront control techniques
to achieve the necessary contrast levels. These correction algorithms are iterative and the control methods
require an estimate of the electric field at the science camera, which requires nearly all of the images taken for
the correction. We demonstrate a Kalman filter estimator that uses prior knowledge to create the estimate of
the electric field, dramatically reducing the number of exposures required to estimate the image plane electric
field. In addition to a significant reduction in exposures, we discuss the relative merit of this algorithm to other
estimation schemes, particularly in regard to estimate error and covariance. As part of the reduction in exposures
we also discuss a novel approach to generating the diversity required for estimating the field in the image plane.
This uses the stroke minimization control algorithm to choose the probe shapes on the deformable mirrors,
adding a degree of optimality to the problem and once again reducing the total number of exposures required
for correction. Choosing probe shapes has been largely unexplored up to this point and is critical to producing
a well posed set of measurements for the estimate. Ultimately the filter will lead to an adaptive algorithm which
can estimate physical parameters in the laboratory and optimize estimation.
Phase induced amplitude apodization (PIAA) coronagraphy: recent results and future prospects
Show abstract
Thanks to the use of aspheric optics for lossless apodization, the Phase Induced Amplitude Apodization (PIAA)
coronagraph offers full throughput, high contrast and small inner working angle. It is therefore ideally suited for space-based
direct imaging of potentially habitable exoplanets. The concept has evolved since its original formulation to
mitigate manufacturing challenges and improve performance. Our group is currently aiming at demonstrating PIAA
coronagraphy in the laboratory to 1e-9 raw contrast at 2 λ/D separation. Recent results from the High Contrast Imaging
Testbed (HCIT) at JPL demonstrate contrasts about one order of magnitude from this goal at 2 λ/D. In parallel with our
high contrast demonstration at 2 λ/D, we are developing and testing new designs to reduce inner working angle and
improve performance in polychromatic light. The newly developed PIAA complex mask coronagraph (PIAACMC)
concept provides total starlight extinction and offers full throughput with a sub- λ/D inner working angles. We also
describe a recent laboratory demonstration of fine pointing control with PIAA.
Count rate nonlinearity in near infrared detectors: inverse persistence
Michael Regan,
Eddie Bergeron,
Kevin Lindsay,
et al.
Show abstract
The count rate non-linearity of near-infrared devices was first found in the HST NICMOS. In this report we present a
physical model of the cause of this effect, show how it is related to persistence, and compare the predictions of the model
to other observations of anomalous detector behavior. This model is able to explain not only the count rate non-linearity
but also several other effects. Overall, the excellent agreement between this model and the observations gives us strong
confidence that we understand the underlying cause of the count rate non-linearity. This understanding should allow us
to develop methods to accurately calibrate and remove the effect from JWST observations.
Photometry of infrared space telescope images using the grid PRF method Dphot
Show abstract
The grid PRF photometry method Dphot detects and measures point sources and extended sources using the Basic
Calibrated Data images from the Spitzer Space Telescope without prior source position information. A mosaic is not
used. Point sources with separations as small as 1.0 arcsec can be detected and measured. Examples of Dphot
photometry are presented for 47 Tuc, the Galactic Center, Einstein Cross, and galaxies in GOODS North.
Phase retrieval on extended sources in the visible and infrared
Show abstract
An iterative Fourier-transform algorithm was implemented to reconstruct the phase function of an imaging
system using a point source (a single mode ber) and extended sources (pinholes) as the object. The results
indicate that as the objects size is increased the phase retrieval is largely unaected until it grows to a critical
diameter. At this point the phase retrieval results become highly unstable. The critical diameter at which this
transition occurs is considerably smaller than predicted by the Rayleigh criterion. In this paper, we will present
a detailed description of the imaging system, the source objects and the experimental results.
Investigation on the high efficiency volume Bragg gratings performances for spectrometry in space environment: preliminary results
Show abstract
The special properties of Volume Bragg Gratings (VBGs) make them good candidates for spectrometry applications
where high spectral resolution, low level of straylight and low polarisation sensitivity are required. Therefore it is of
interest to assess the maturity and suitability of VBGs as enabling technology for future ESA missions with demanding
requirements for spectrometry. The VBGs suitability for space application is being investigated in the frame of a project
led by CSL and funded by the European Space Agency. The goal of this work is twofold: first the theoretical advantages
and drawbacks of VBGs with respect to other technologies with identical functionalities are assessed, and second the
performances of VBG samples in a representative space environment are experimentally evaluated.
The performances of samples of two VBGs technologies, the Photo-Thermo-Refractive (PTR) glass and the
DiChromated Gelatine (DCG), are assessed and compared in the Hα, O2-B and NIR bands. The tests are performed
under vacuum condition combined with temperature cycling in the range of 200 K to 300K. A dedicated test bench
experiment is designed to evaluate the impact of temperature on the spectral efficiency and to determine the optical
wavefront error of the diffracted beam. Furthermore the diffraction efficiency degradation under gamma irradiation is
assessed. Finally the straylight, the diffraction efficiency under conical incidence and the polarisation sensitivity is
evaluated.
Experimental parametric study of the self-coherent camera
Show abstract
Direct imaging of exoplanets requires the detection of very faint objects orbiting close to very bright stars. In this context, the SPICES mission was proposed to the European Space Agency for planet characterization at visible wavelength. SPICES is a 1.5m space telescope which uses a coronagraph to strongly attenuate the central source. However, small optical aberrations, which appear even in space telescopes, dramatically decrease coronagraph performance. To reduce these aberrations, we want to estimate, directly on the coronagraphic image, the electric field, and, with the help of a deformable mirror, correct the wavefront upstream of the coronagraph. We propose an instrument, the Self-Coherent Camera (SCC) for this purpose. By adding a small "reference hole" into the Lyot stop, located after the coronagraph, we can produce interferences in the focal plane, using the coherence of the stellar light. We developed algorithms to decode the information contained in these Fizeau fringes and retrieve an estimation of the field in the focal plane. After briefly recalling the SCC principle, we will present the results of a study, based on both experiment and numerical simulation, analyzing the impact of the size of the reference hole.
Qualification of a null lens using image-based phase retrieval
Show abstract
In measuring the figure error of an aspheric optic using a null lens, the wavefront contribution from the null lens must be
independently and accurately characterized in order to isolate the optical performance of the aspheric optic alone.
Various techniques can be used to characterize such a null lens, including interferometry, profilometry and image-based
methods. Only image-based methods, such as phase retrieval, can measure the null-lens wavefront in situ – in single-pass,
and at the same conjugates and in the same alignment state in which the null lens will ultimately be used – with no
additional optical components. Due to the intended purpose of a null lens (e.g., to null a large aspheric wavefront with a
near-equal-but-opposite spherical wavefront), characterizing a null-lens wavefront presents several challenges to image-based
phase retrieval: Large wavefront slopes and high-dynamic-range data decrease the capture range of phase-retrieval
algorithms, increase the requirements on the fidelity of the forward model of the optical system, and make it difficult to
extract diagnostic information (e.g., the system F/#) from the image data. In this paper, we present a study of these
effects on phase-retrieval algorithms in the context of a null lens used in component development for the Climate
Absolute Radiance and Refractivity Observatory (CLARREO) mission. Approaches for mitigation are also discussed.
End-to-end coronagraphic modeling including a low-order wavefront sensor
Show abstract
To evaluate space-based coronagraphic techniques, end-to-end modeling is necessary to simulate realistic fields
containing speckles caused by wavefront errors. Real systems will suffer from pointing errors and thermal and motioninduced
mechanical stresses that introduce time-variable wavefront aberrations that can reduce the field contrast. A loworder
wavefront sensor (LOWFS) is needed to measure these changes at a sufficiently high rate to maintain the contrast
level during observations. We implement here a LOWFS and corresponding low-order wavefront control subsystem
(LOWFCS) in end-to-end models of a space-based coronagraph. Our goal is to be able to accurately duplicate the effect
of the LOWFS+LOWFCS without explicitly evaluating the end-to-end model at numerous time steps.
Optimized shaped pupil masks for pupil with obscuration
Show abstract
The main components of the SPICA coronagraphic instrument have initially been bar-code apodizing masks,
i.e. shaped pupils optimized in one dimension. Their free-standing designs make them manufacturable without
a glass substrate, which implies an absolute achromaticity and no additional wavefront errors. However, shaped
pupils can now be optimized in two dimensions and can thus take full advantage of the geometry of any arbitrary
aperture, in particular obstructed apertures such as SPICA's. Hence, 2D shaped pupils often have higher
throughputs while offering the same angular resolutions and contrast. Alternatively, better resolutions or contrast
can be obtained for the same throughput. Although some of these new masks are free-standing, this property
cannot be constrained if the optimization problem has to remain convex linear. We propose to address this
issue in different ways, and we present here examples of freestanding masks for a variety of contrasts, and
inner working angles. Moreover, in all other coronagraphic instruments, contrast smaller than 10-5 can only
be obtained if a dedicated adaptive optics system uses one or several deformable mirrors to compensate for
wavefront aberrations. The finite number of actuators sets the size of the angular area in which quasi-static
speckles can be corrected. This puts a natural limit on the outer working angle for which the shaped pupils
are designed. The limited number of actuators is also responsible for an additional diffracted energy, or quilting
orders, that can prevent faint companions to be detected. This effect can and must be taken into account in
the optimization process. Finally, shaped pupils can be computed for a given nominal phase aberration pattern
in the pupil plane, although the solutions depend in this case on the observation wavelength. We illustrate this
possibility by optimizing an apodizer for the James Webb space telescope, and by testing its chromaticity and
its robustness to phase changes.
Adaptive optics operation with two wavefront sensors in a coronagraph for exoplanet observations
Show abstract
A stellar coronagraph system for direct observations of extra solar planets is under development by combining
unbalanced nulling interferometer (UNI), adaptive optics, and a focal plane coronagraph 1, 2, 3, 4, 5. It can reach a high
contrast as using lambda/10000 precision optics by lambda/1000 quality ones. However, a sufficiently high contrast has
yet to be obtained for the experiment. It is thought that the remaining speckle noise at the final coronagraph focal plane
detector is produced by a “non-common path error” of lambda/100 level, which is a wavefront error of differences
between the coronagraph and a wavefront sensor (WFS) of adaptive optics, even when the WFS indicates lambda/1000
conversion. The non-common path error can be removed by the focal plane sensing method of wavefront correction by
wavefront sensing at the final focal plane detector, although it has an issue of operation for very faint targets because of a
slow feedback loop. In the present paper, we describe how our coronagraph system becomes practically higher contrast
by upgrading the control method of adaptive optics with the WFS assisted by a focal plane wavefront sensing. Then, we
control a wavefront error by two feedback loops, the first of which uses a WFS to make fast control for telescope optics
deformation and the second of which uses a focal plane detector to compensate for the non-common path error with slow
control. We show experiment results of the coronagraph system performance with both wavefront sensing methods.
Development of CdZnTe immersion grating for spaceborne application
Show abstract
We have been developing an immersion grating for high-resolution spectroscopy in the mid-infrared (MIR)
wavelength region. A MIR (12-18 µm) high-resolution (R = 20,000-30,000) spectrograph with the immersion
grating is proposed for SPICA, Japanese next-generation space telescope. The instrument will be the world's first
high-resolution spectrograph in space, and it would make great impacts on infrared astronomy. To realize a high-efficiency immersion grating, optical properties and machinability of bulk materials are the critical issues. There
are three candidate materials with good MIR transmittance; CdTe (n = 2.65), CdZnTe (n = 2.65), and KRS5 (n
= 2.30). From measurements of transmittance with FTIR and of homogeneity with phase-shifting interferometry
at 1.55 μm, we confirmed that CdZnTe is the best material that satisfies all the optical requirements. As for
machinability, by applying Canon's diamond cutting (planing) technique, fine grooves that meet our requirement
were successfully cut on flats for all the materials. We also managed to fabricate a small CdZnTe immersion
grating, which shows a high grating efficiency from the air. For the reflective metal coating, we tried Au (with
thin underlying layer of Cr) and Al on CdZnTe flats both by sputter deposition and vapor deposition. All samples
are found to be robust under 77 K and some of them achieve required reflectivity. Despite several remaining
technical issues, the fabrication of CdZnTe immersion grating appears to be sound.
How Earth atmospheric radiations may affect astronomical observations from low-orbit satellites
Show abstract
Telescopes are placed on spacecrafts to avoid the effects of the Earth atmosphere on astronomical observations
(turbulence, extinction ...). Atmospheric effects however may subsist when satellites are launched in low orbits,
typically mean altitudes of the order of 700 km. We will present first in this paper how we are able to estimate
the mean Earth radiation flux when we consider temperature housekeeping data recorded with a specific space
solar mission having this orbit property. We will show after how some solar parameters extracted from images
recorded with the on-board telescope are correlated with the Earth atmospheric radiation flux. We will also
present how we find the limits of the South Atlantic Anomaly from affected images.
A laboratory experiment for a new free-standing pupil mask coronagraph
K. Haze,
K. Enya,
T. Kotani,
et al.
Show abstract
This paper presents the results of a laboratory experiment on a new free-standing pupil mask coronagraph for the direct
observation of exoplanets. We focused on a binary-shaped pupil coronagraph, which is planned for installation in the
next-generation infrared space telescope SPICA. Our laboratory experiments on the coronagraph were implemented
inside a vacuum chamber (HOCT) to achieve greater thermal stability and to avoid air turbulence, and a contrast of
1.3×10-9 was achieved with PSF subtraction. We also carried out multi-color/broadband experiments to demonstrate that
the pupil mask coronagraph works, in principle, at all wavelengths. We had previously manufactured a checker-board
mask, a type of binary-shaped pupil mask, on a glass substrate, which had the disadvantages of light loss by transmission,
ghosting from residual reflectance and a slightly different refractive index for each wavelength. Therefore, we developed
a new free-standing mask in sheet metal, for which no substrate was needed. As a result of a He-Ne laser experiment
with the free-standing mask, a contrast of 1.0×10−7 was achieved for the raw coronagraphic image. We also conducted
rotated mask subtractions and numerical simulations of some errors in the mask shape and WFEs. Speckles are the major
limiting factor. The free-standing mask exhibited about the same ability to improve contrast as the substrate mask.
Consequently, the results of this study suggest that the binary-shaped pupil mask coronagraph can be applied to
coronagraphic observations by SPICA and other telescopes.
Prototype-testbed for infrared optics and coronagraph (PINOCO)
K. Enya,
K. Haze,
K. Arimatsu,
et al.
Show abstract
We present the Prototype-testbed for Infrared Optics and Coronagraphs (PINOCO) which is a large, multi-purpose
cryogenic chamber. At present, the priority for PINOCO is to evaluate binary pupil mask coronagraphs in the mid-infrared
wavelength region, which are planned to be adopted for the SPICA coronagraph instrument. In addition, various
other experiments are possible using PINOCO: testing diverse high dynamic-range techniques, mirrors, active optics,
infrared detectors, filters and spectral dispersion devices, the mechanics of the instruments, measurement of material
properties, and so on. PINOCO provides a work space of 1m × 1m × 0.3m, of which inside is cooled to <5K.
Flexible access to the work surface is possible by removing detachable plates at the four sides and on the top of the
chamber. At the interface to the exterior, PINOCO is currently equipped with an optical window, electric
connectors, and an interferometer stage. PINOCO is cooled by two GM-cycle cryo-coolers, so no cryogen is
needed. A cooling test of PINOCO was successfully completed.
A coronagraph system with unbalanced nulling interferometer: progress of dynamic range
Show abstract
We have studied a coronagraph system with an unbalanced nulling interferometer (UNI). It consists of the UNI, adaptive
optics, and a coronagraph. An important characteristic is a magnification of the wavefront aberrations in the UNI stage,
which enables us to compensate for the wavefront aberrations beyond the AO systems capabilities. In our experiments,
we have observed the stable aberration magnification of about 6 times and compensation to about λ/100 rms
corresponding to λ/600 rms virtually. As a result, at the final focal plane of a 3-dimensional Sagnac interferometric
nulling coronagraph, we have obtained the extra speckle reduction of better than 0.07 by the advantage of the UNI-PAC
system. In order to obtain better contrast, we consider improvement of the optics with an 8OPM coronagraph, a dual
feedback control, an unbalanced nulling interferometer with 4QPM or VVM, and a wavefront correction inside the UNI.