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- Front Matter: Volume 7731
- Strategies
- JWST I
- JWST II
- JWST III
- AKARI/Spitzer
- SPICA I
- SPICA II
- WISE
- Hubble
- Herschel
- Kepler
- Solar Planetary
- GAIA
- JDEM
- Euclid
- Systems Concepts I
- Systems Concepts II
- Systems Concepts III
- Systems Concepts IV
- TPF Coronagraph
- TPF Occulter
- ATLAST
- Late Breaking News
- Poster Session: AKARI
- Poster Session: ATLAST
- Poster Session: Euclid
- Poster Session: GAIA
- Poster Session: Herschel
- Poster Session: Hubble
- Poster Session: Instruments
- Poster Session: JDEM
- Poster Session: JWST
- Poster Session: Mirror Technology
- Poster Session: nJASMINE
- Poster Session: Solar Planetary Science
- Poster Session: SPICA
- Poster Session: Strategies
- Poster Session: Systems Concepts
- Poster Session: TPF C
- Poster Session: TPF Occulter
- Poster Session: WFSC
Front Matter: Volume 7731
Front Matter: Volume 7731
Show abstract
This pdf file contains the front matter associated with SPIE Proceedings Volume 7731, including Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
Strategies
Key enabling technologies for the next generation of space telescopes
Show abstract
The next generation of large space telescopes, including ATLAST, SAFIR, IXO and Generation-X will require the
development of key technologies to enable their development at an affordable cost. This includes technologies for the
rapid, low cost fabrication of ultra-light weight primary mirror segments, active figure control of primary mirror
segments, high speed wavefront sensing and control, highly-packageable and scalable deployment techniques, and active
vibration and thermal control for light weight structural elements to supply good pointing stability. In this paper we
discuss the current state-of-the-art for these technologies and roadmaps for future development in these areas.
Early results from NASA's assessment of satellite servicing
Show abstract
Following recommendations by the NRC, NASA's FY 2008 Authorization Act and the
FY 2009 and 2010 Appropriations bills directed NASA to assess the use of the human
spaceflight architecture to service existing/future observatory-class scientific spacecraft.
This interest in satellite servicing, with astronauts and/or with robots, reflects the success
that NASA achieved with the Shuttle program and HST on behalf of the astronomical
community as well as the successful construction of ISS. This study, led by NASA
GSFC, will last about a year, leading to a final report to NASA and Congress in autumn
2010. We will report on its status, results from our March satellite servicing workshop,
and recent concepts for serviceable scientific missions.
Preliminary multivariable cost model for space telescopes
Show abstract
Parametric cost models are routinely used to plan missions, compare concepts and justify technology investments. This
paper reviews the methodology used to develop space telescope cost models; summarizes recently published single
variable models; and presents preliminary results for two and three variable cost models. Some of the findings are that
increasing mass reduces cost; it costs less per square meter of collecting aperture to build a large telescope than a small
telescope; and technology development as a function of time reduces cost at the rate of 50% per 17 years.
JWST I
Overview of the James Webb Space Telescope Observatory
Show abstract
The James Webb Space Telescope (JWST) is a large aperture, space telescope designed to provide imaging and
spectroscopy from 1.0 μm to 28 μm. JWST will be launched to an orbit at L2 aboard an Ariane 5 launcher in 2013. The
Goddard Space Flight Center (GSFC) is the lead center for the JWST program and manages the project for NASA. The
prime contractor for JWST is Northrop Grumman Aerospace Systems (NGST). JWST is an international partnership
with the European Space Agency (ESA), and the Canadian Space Agency (CSA). ESA will contribute the Ariane 5
launch, and a multi-object infrared spectrograph. CSA will contribute the Fine Guidance Sensor (FGS), which includes
the Tunable Filter Imager (TFI). The European consortium, in collaboration with the Jet Propulsion Laboratory (JPL),
builds the mid-infrared imager (MIRI). In this paper we present an overview of the JWST science program, and discuss
recent progress in the development of the observatory.
Status of the James Webb Space Telescope integrated science instrument module system
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 II
Results, status, and plans for the James Webb Space Telescope optical telescope element
Show abstract
The James Webb Space Telescope (JWST) Optical Telescope Element has completed its Critical Design Review and is
well into fabrication. This paper will summarize efforts to date in the design, manufacturing and planning for integration
and testing. This will include a top level summary of mirror performance to date, hardware results, and planning status
for the integration and testing program. The future plans for manufacturing, assembly, alignment and testing will also be
summarized at a top level.
Optical performance for the actively controlled James Webb Space Telescope
Show abstract
The James Webb Space Telescope (JWST) is a large space based astronomical telescope that will operate at
cryogenic temperatures. The telescope by virtue of its size must be stowed in an inoperable configuration for launch
and remotely reconfigured in space to meet the operational requirements using active Wave Front Sensing and
Control (WFSC). This paper will report on the optical budgeting process used to manage the performance of the
active system. The current status of the design and verification of the optical hardware, the WFSC processes, and
the total system verification modeling will be presented. More detailed discussions of the system verification by
analysis will be presented in separate accompanying papers.
NIRCam: development and testing of the JWST near-infrared camera
Show abstract
The Near Infrared Camera (NIRCam) is one of the four science instruments of the James Webb Space Telescope
(JWST). Its high sensitivity, high spatial resolution images over the 0.6 - 5 μm wavelength region will be
essential for making significant findings in many science areas as well as for aligning the JWST primary mirror
segments and telescope. The NIRCam engineering test unit was recently assembled and has undergone successful
cryogenic testing. The NIRCam collimator and camera optics and their mountings are also progressing, with a
brass-board system demonstrating relatively low wavefront error across a wide field of view. The flight model's
long-wavelength Si grisms have been fabricated, and its coronagraph masks are now being made. Both the short
(0.6 - 2.3 μm) and long (2.4 - 5.0 μm) wavelength flight detectors show good performance and are undergoing
final assembly and testing. The flight model subsystems should all be completed later this year through early
2011, and NIRCam will be cryogenically tested in the first half of 2011 before delivery to the JWST integrated
science instrument module (ISIM).
Status of the NIRSpec instrument
Stephan M. Birkmann,
Torsten Böker,
Peter Jakobsen,
et al.
Show abstract
The Near Infrared Spectrograph (NIRSpec) is one of the four science instruments aboard the James Webb Space
Telescope (JWST) scheduled for launch in 2014. NIRSpec is sensitive in the wavelength range from ~ 0.6 to
5.0 μm and will be capable of obtaining spectra of more than a 100 objects simultaneously, as well as fixed slit
high contrast spectroscopy of individual sources. It also features an integral field unit for 3D spectroscopy. The
key scientific objectives of the instrument include studies of star formation and chemical abundances of young
distant galaxies and tracing the creation of the chemical elements back in time. In this paper, we present the
status of the NIRSpec instrument as it is currently being prepared for its extensive ground calibration campaign
later in 2010.
Progress with the design and development of MIRI, the mid-IR instrument for JWST
Show abstract
MIRI is one of four instruments to be built for the James Webb Space Telescope. It provides imaging, coronography and
integral field spectroscopy over the 5-28.5um wavelength range. MIRI is the only instrument which is cooled to 7K by a
dedicated cooler, much lower than the passively cooled 40K of the rest of JWST, and consists of both an Optical System
and a Cooler System. This paper will describe the key features of the overall instrument design and then concentrate on
the status of the MIRI Optical System development. The flight model design and manufacture is complete, and final
assembly and test of the integrated instrument is now underway. Prior to integration, all of the major subassemblies have
undergone individual environmental qualification and performance tests and end-end testing of a flight representative
model has been carried out. The paper will provide an overview of results from this testing and describe the current
status of the flight model build and the plan for performance verification and ground calibration.
The JWST tunable filter imager (TFI)
Show abstract
The Fine Guidance Sensor (FGS) of the James Webb Space Telescope (JWST) features a tunable filter imager (TFI)
module covering the wavelength range from 1.5 to 5.0 μm at a resolving power of ~100 over a field of view of
2.2'×2.2'. TFI also features a set of occulting spots and a non-redundant mask for high-contrast imaging. This paper
presents the current status of the TFI development. The instrument is currently under its final integration and test phase.
JWST III
Successful production of the engineering development unit (EDU) primary mirror segment and flight unit tertiary mirror for JWST
Show abstract
During 2009, Tinsley finished most of the Configuration 1 pre-cryo test Computer Controlled Optical Surfacing (CCOS)
operations on the James Webb Space Telescope primary mirror segments and in mid-2009 we began the Configuration 2
post-cryo test CCOS operations. After completing the grinding and polishing operations, including final figuring to a
cryo-null target, we delivered the finished Engineering Development Unit (EDU) to Ball Aerospace Technology
Corporation on 4 December 2009. Achieving fabrication and metrology conditions to meet the specifications for this off-axis
~1.5 m hexagonal point-to-point segmented mirror required special methods. Achieving repeatable and accurate
interferometric alignment of the off-axis aspherical mirror surface and stable thermal gradient control of the beryllium
substructure during tests required rigorous component and system-level validation. Final optical wavefront
measurements over the various spatial frequency ranges have demonstrated that all of the requirements are met. This
success has validated our processes of fabrication and metrology and allows us to proceed with the production of the 18
flight mirror segments. The first finished flight mirror, the Tertiary Mirror, was shipped to BATC on 24 February, 2010.
Performance of that mirror is reported here also.
Optical performance of the JWST/MIRI flight model: characterization of the point spread function at high resolution
Show abstract
The Mid Infra Red Instrument (MIRI) is one of the four instruments onboard the James Webb Space Telescope (JWST),
providing imaging, coronagraphy and spectroscopy over the 5 - 28 μm band. To verify the optical performance of the
instrument, extensive tests were performed at CEA on the flight model (FM) of the Mid-InfraRed IMager (MIRIM) at
cryogenic temperatures and in the infrared. This paper reports on the point spread function (PSF) measurements at 5.6 μm,
the shortest operating wavelength for imaging. At 5.6 μm, the PSF is not Nyquist-sampled, so we use am original technique
that combines a microscanning measurement strategy with a deconvolution algorithm to obtain an over-resolved MIRIM
PSF. The microscanning consists in a sub-pixel scan of a point source on the focal plane. A data inversion method is used
to reconstruct PSF images that are over-resolved by a factor of 7 compared to the native resolution of MIRI. We show that
the FWHM of the high-resolution PSFs were 5 - 10 % wider than that obtained with Zemax simulations. The main cause
was identified as an out-of-specification tilt of the M4 mirror. After correction, two additional test campaigns were carried
out, and we show that the shape of the PSF is conform to expectations. The FWHM of the PSFs are 0.18 - 0.20 arcsec,
in agreement with simulations. 56.1 - 59.2% of the total encircled energy (normalized to a 5 arcsec radius) is contained
within the first dark Airy ring, over the whole field of view. At longer wavelengths (7.7 - 25.5 μm), this percentage is
57 - 68 %. MIRIM is thus compliant with the optical quality requirements. This characterization of the MIRIM PSF, as
well as the deconvolution method presented here, are of particular importance, not only for the verification of the optical
quality and the MIRI calibration, but also for scientific applications.
The throughput and sensitivity of the JWST mid-infrared instrument
Show abstract
The Verification Model (VM) of MIRI has recently completed an extensive programme of cryogenic testing, with the
Flight Model (FM) now being assembled and made ready to begin performance testing in the next few months. By
combining those VM test results which relate to MIRI's scientific performance with measurements made on FM
components and sub-assemblies, we have been able to refine and develop the existing model of the instrument's
throughput and sensitivity.
We present the main components of the model, its correlation with the existing test results and its predictions for
MIRI's performance on orbit.
Testing a critical stray light path of the James Webb Space Telescope
Show abstract
The James Webb Space Telescope (JWST) requires cryogenic testing of a critical stray light path, named as the Rogue Path. Although blockage of this path is verified during fabrication and assembly of JWST, simple small light sources added to the test configuration provide an opportunity to check for successful blockage at the system level in the cryogenic environment. Although the test occurs in the largest environmental chamber at the NASA Johnson Space Center, the size of the chamber challenges this test by placing the origin of the Rogue Path within the collimated beam of the telescope. The design of the test overcomes this challenge with sufficient signal to noise ratio and without interference with the optical test of the system.
AKARI/Spitzer
AKARI warm mission
Show abstract
AKARI, the Japanese satellite mission dedicated for infrared astronomy launched in 2006 February, exhausted its 180
litter liquid helium (LHe) in 2007 August. After the LHe exhaustion, the telescope and focal plane of AKARI have still
been kept less than 50K by the onboard cryocooler and near-infrared (NIR) observations with the Infrared Camera (IRC)
are continuing. The data reduction software optimized for the warm mission enables us to carry out efficient and
sensitive observations in the NIR despite the increase of hot pixels. In particular, the NIR spectroscopic capability of
the IRC provides a unique opportunity to obtain spectra in 2.5-5μm with a high sensitivity, which will not be able to be
carried out with any other facilities until JWST. An overview of the AKARI warm mission is given together with the
performance and some observational results taken during the warm mission.
Calibration and data quality of warm IRAC
Show abstract
We present an overview of the calibration and properties of data from the IRAC instrument aboard the Spitzer Space
Telescope taken after the depletion of cryogen. The cryogen depleted on 15 May 2009, and shortly afterward a two-month-
long calibration and characterization campaign was conducted. The array temperature and bias setpoints were
revised on 19 September 2009 to take advantage of lower than expected power dissipation by the instrument and to
improve sensitivity. The final operating temperature of the arrays is 28.7 K, the applied bias across each detector is 500
mV and the equilibrium temperature of the instrument chamber is 27.55 K. The final sensitivities are essentially the
same as the cryogenic mission with the 3.6 μm array being slightly less sensitive (10%) and the 4.5 μm array within 5%
of the cryogenic sensitivity. The current absolute photometric uncertainties are 4% at 3.6 and 4.5 μm, and better than
milli-mag photometry is achievable for long-stare photometric observations. With continued analysis, we expect the
absolute calibration to improve to the cryogenic value of 3%. Warm IRAC operations fully support all science that was
conducted in the cryogenic mission and all currently planned warm science projects (including Exploration Science
programs). We expect that IRAC will continue to make ground-breaking discoveries in star formation, the nature of the
early universe, and in our understanding of the properties of exoplanets.
SPICA I
The next-generation space infrared astronomy mission SPICA
Show abstract
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid- and
far-infrared astronomy with a cryogenically cooled 3-m class (3.2 m in the current design) telescope. Its high spatial
resolution and unprecedented sensitivity in the mid- and far-infrared 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. The most important international partner is ESA. The assessment study on the
European contribution to the SPICA project has started under the framework of the ESA Cosmic Vision 2015-2025. US
and Korean participations are also being discussed extensively. The target launch year of SPICA is FY2018.
System requirements and design concept of the SPICA Mission
Show abstract
SPICA is a next generation infrared astronomy mission to reveal the origin of planets and galaxies. The mission is led by
Japan Aerospace Exploration Agency (JAXA) in collaboration with the European Space Agency (ESA) and international
consortiums in Japan, Europe, USA, and the Republic of Korea. SPICA is an "observatory" based on the heritage of
AKARI's "all sky survey". ESA provides a 3-m class telescope using technology heritage of Herschel. The SPICA will
achieve superior sensitivity in the mid- to far- infrared astronomy to be launched into space. SPICA has a completely
new cooling system, which utilizes efficient mechanical coolers. This system enables a large, cryogenically cooled
telescope in space. SPICA system concept and requirements are clear, but it is not easy to design. SPICA spacecraft
consists of the Payload Module (PLM) and the Bus Module (BM). The PLM includes mechanical coolers and passive
thermal shields, which enable to cool down the telescope and scientific instruments below 6K. The PLM is connected to
the BM with low thermal conductivity truss structure to keep the PLM cool and the BM warm. This paper describes how
to meet the system requirements to establish the feasible design of SPICA spacecraft.
Conceptual design for the mid-infrared medium-resolution Echelle spectrometer (MIRMES) on the SPICA Mission
Show abstract
The Mid-Infrared Medium-Resolution Eschelle Spectrometer (MIRMES) is one of the focal-plane instrument onboard
SPICA mission proposed in the pre-project phase. It is designed for measuring the strengths and the profiles of lines and
bands emitted from various phases of materials including ionized gas, gas-phase molecules, solid-phase molecules and
dust particles in the wavelengths from 10 to 40μm. The MIRMES provides a medium resolution (R=700-1500)
spectroscopic capability in the mid-infrared spectral range (10-36μm) with integrated field units of a field-of-view of
about 12"×6" for shorter wavelength range (10-20μm) and 12"×12".5 for longer wavelength range (20-36μm). The
science targets of the MIRMES and the results of the concept study on its optical design and the expected performance
are described.
SPICA II
The background-limited infrared-submillimeter spectrograph (BLISS) for SPICA: a design study
Show abstract
We are developing the Background-Limited Infrared-Submillimeter Spectrograph (BLISS) for SPICA to provide
a breakthrough capability for far-IR survey spectroscopy. SPICAs large cold aperture 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 is 6 orders of magnitude faster than the spectrometers on Herschel and
SOFIA in obtaining full-band spectra. It enables spectroscopy of dust-obscured galaxies at all epochs back to
the rst billion years after the Big Bang (redshift 6), and study of all stages of planet formation in circumstellar
disks.
BLISS covers 35 - 433 microns range in ve or six wavelength bands, and couples two 2 sky positions simultaneously.
The instrument is cooled to 50 mK for optimal sensitivity with an on-board refrigerators. The detector
package is 4224 silicon-nitride micro-mesh leg-isolated bolometers with superconducting transition-edge-sensed
(TES) thermistors, read out with a cryogenic time-domain multiplexer. All technical elements of BLISS have
heritage in mature scientic instruments, and many have own. We report on our design study in which we are
optimizing performance while accommodating SPICAs constraints, including the stringent cryogenic mass budget.
In particular, we present our progress in the optical design and waveguide spectrometer prototyping. A
companion paper in Conference 7741 (Beyer et al.) discusses in greater detail the progress in the BLISS TES
bolometer development.
WISPIR: a wide-field imaging spectrograph for the infrared for the SPICA Observatory
Show abstract
We have undertaken a study of a far infrared imaging spectrometer based on a Fourier transform spectrometer that uses
well-understood, high maturity optics, cryogenics, and detectors to further our knowledge of the chemical and
astrophysical evolution of the Universe as it formed planets, stars, and the variety of galaxy morphologies that we
observe today. The instrument, Wide-field Imaging Spectrometer for the InfraRed (WISPIR), would operate on the
SPICA observatory, and will feature a spectral range from 34 - 210 microns and a spectral resolving power of R=1,000
to 6,000, depending on wavelength. WISPIR provides a choice of full-field spectral imaging over a 2'×2' field or longslit
spectral imaging along a 2' slit for studies of astrophysical structures in the local and high-redshift Universe. WISPIR
in long-slit mode will attain a sensitivity two orders of magnitude better than what is currently available.
Mid-infrared camera without lens (MIRACLE) for SPICA
Show abstract
Mid-InfRAred Camera w/o LEns (MIRACLE) is a focal plane instrument for the future JAXA/ESA infrared
astronomical mission, SPICA. MIRACLE is designed for wide field imaging (5' × 5') and low-resolution spectroscopic
observations (R~100) over a wide spectral range in the mid-infrared wavelengths (5-38μm). Thanks
to the SPICA's large aperture (3-m class) and cold (<6K) telescope, MIRACLE has a better sensitivity than
JWST/MIRI at the wavelength over 20μm (3.5 μJy at 20μm, R=5, S/N=5, 3600 seconds) and its wider field
of view (FOV) provides a faster mapping speed in its full spectral range for point sources. Confocal off-axis
reflective imaging system provides a wide FOV with diffraction limited image quality over wide spectral range.
MIRACLE consists of two channels: MIRACLE-S and MIRACLE-L, which are optimized for 5-26μm and 20-
38μm, respectively. Each of them consists of a fore-optics and a rear-optics, each of which has a pupil position
equipped with a filter wheel and a grating wheel, respectively. A field stop wheel, which provides optimal slits in
the spectroscopic mode and a wide FOV in the imaging mode, is installed at the focal plane of the fore-optics.
A large format array detector (Si:As 2K×2K for MIRACLE-S and Si:Sb 1K×1K for MIRACLE-L) is installed at
the focal plane of the rear-optics in order to achieve Nyquist sampling of the point spread function. Contiguous
wavelength coverage is considered in choice of the filter bands from the experiences in the Spitzer and AKARI
observations. We will present the results of conceptual design study including sensitivity analysis.
Optical testing activities for the SPICA telescope
Show abstract
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a Japan-led infrared astronomical satellite project
with a 3-m-class telescope in collaboration with Europe. The telescope is cooled down to temperature below 6 K in space
by a combination of mechanical coolers with radiative cooling in space. The telescope has requirements for its total
weight to be lighter than 700 kg and for the imaging performance to be diffraction-limited at 5 μm at 6 K. The mirrors
will be made of silicon carbide (SiC) or its related material, which has large heritages of the AKARI and Herschel
telescopes. The design of the telescope system has been studied by the Europe-Japan telescope working group led by
ESA with European industries to meet the requirements. As for optical testing, responsibilities will be split between
Europe and Japan so that final optical verification at temperatures below 10 K will be executed in Japan. We present our
recent optical testing activities in Japan for the SPICA telescope, which include the numerical and experimental studies
of stitching interferometry as well as modifications of the 6-m-diameter radiometer space chamber facility at Tsukuba
Space Center in JAXA. We also show results of cryogenic optical testing of the 160-mm and 800-mm lightweight
mirrors made of a C/SiC material called HBCesic, which is a candidate mirror material for the SPICA telescope.
WISE
Pre-launch characterization of the WISE payload
Show abstract
The Wide-field Infrared Survey Explorer (WISE), launched in December 2009, is a NASA-funded Explorer mission that
is providing an all-sky survey in the mid-infrared with far greater sensitivity and resolution than any previous IR survey
mission. The Utah State University Space Dynamics Laboratory designed, fabricated, and characterized the science
payload, which is a cryogenically cooled infrared telescope with four 1024x1024 infrared focal plane arrays covering
from 2.8 to 26 μm. Pre-launch characterization included measuring focus, image quality, repeatability, response nonlinearity,
saturation, latency, absolute response, flatfield, point response function, scanner linearity, and relative spectral
response. This paper provides a brief overview of the payload, discusses pre-launch characterization methods, and
presents key performance results from ground characterization and early on-orbit performance.
Hardware results for the Wide-field Infrared Survey Explorer (WISE) telescope and scanner
Show abstract
On December 14, 2009 NASA launched the Wide-field Infrared Survey Explorer (WISE), a NASA MIDEX mission
within the Explorers program that is currently performing an all-sky survey in four infrared bands. L-3 Integrated
Optical Systems/SSG designed, built, and tested the telescope, scanner, and aft imaging optical system for WISE under
contract to the Space Dynamics Laboratory. Hardware and test results for those subsystems are presented, as well as an
on-orbit status of their imaging performance. The WISE payload includes a 40 cm afocal telescope, a scan mirror for
back-scan during integration, and an aft optics imager assembly. All modules operate below 17 Kelvin. The allreflective
system uses aluminum mirrors and metering structures. The afocal telescope provides distortion control to
better than two parts in a thousand to prevent image blur during internal scanning. The one-axis scan mirror at the exit
pupil scans the detectors' field-of-view across the telescope field-of-regard, countering the orbital motion and freezing
the line of sight during the multi-second exposure period. The five-mirror imaging optics module follows the scan
mirror and feeds dichroic beamsplitters that separate the energy into four channels between 2.8 and 26 microns. Once
initial on-orbit checkout and calibration was completed, WISE began a 6-month mission performing an all-sky survey in
the four infrared bands, which is over 80% complete as of June 2010.
Hubble
On-orbit performance of HST Wide Field Camera 3
Show abstract
The Wide Field Camera 3 (WFC3) was installed into the Hubble Space Telescope during Servicing Mission 4 in May
2009. This panchromatic camera considerably improves the ultraviolet, visible, and infrared imaging capabilities of
HST. Commissioned over the summer of 2009, WFC3 is now fully functional and responsible for approximately half of
the Cycle 17 HST Science Program. This paper will review the scientific performance of WFC3 including its sensitivity
in absolute terms and relative to other HST instruments. The paper will also discuss the calibration programs for WFC3
and the achieved photometric and astrometric calibration accuracies. Lessons learned from the ground calibration and in-flight
commissioning will also be considered.
Feasibility of exoplanet coronagraphy with the Hubble Space Telescope
Show abstract
Herein we report on a preliminary study to assess the use of the Hubble Space Telescope (HST) for the direct detection
and spectroscopic characterization of exoplanets and debris disks - an application for which HST was not originally
designed. Coronagraphic advances may enable the design of a science instrument that could achieve limiting contrasts
~109 beyond 275 milli-arcseconds (4 λ/D at 800 nm) inner working angle, thereby enabling detection and
characterization of several known jovian planets and imaging of debris disks. Advantages of using HST are that it
already exists in orbit, it's primary mirror is thermally stable and it is the most characterized space telescope yet flown.
However there is drift of the HST telescope, likely due to thermal effects crossing the terminator. The drift, however, is
well characterized and consists of a larger deterministic components and a smaller stochastic component. It is the effect
of this drift versus the sensing and control bandwidth of the instrument that would likely limit HST coronagraphic
performance. Herein we discuss the science case, quantify the limiting factors and assess the feasibility of using HST for
exoplanet discovery using a hypothetical new instrument.
Herschel
In-orbit performance of the Herschel/SPIRE imaging Fourier transform spectrometer
Show abstract
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onboard the European
Space Agency's Herschel Space Observatory launched on 14 May 2009. The low to medium resolution spectroscopic
capability of SPIRE is provided by an imaging Fourier transform spectrometer of the Mach-Zehnder configuration.
Results from the in flight performance verification phase of the SPIRE spectrometer are presented and conformance with
the instrument design specifications is reviewed.
Kepler
Kepler instrument performance: an in-flight update
Show abstract
The Kepler Mission is designed to detect the 80 parts per million (ppm) signal from an Earth-Sun equivalent
transit. Such precision requires superb instrument stability on time scales up to 2 days and systematic error
removal to better than 20 ppm. The sole scientific instrument is the Photometer, a 0.95 m aperture Schmidt
telescope that feeds the 94.6 million pixel CCD detector array, which contains both Science and Fine Guidance
Sensor (FGS) CCDs. Since Kepler's launch in March 2009, we have been using the commissioning and science
operations data to characterize the instrument and monitor its performance. We find that the in-flight detector
properties of the focal plane, including bias levels, read noise, gain, linearity, saturation, FGS to Science crosstalk,
and video crosstalk between Science CCDs, are essentially unchanged from their pre-launch values. Kepler's
unprecedented sensitivity and stability in space have allowed us to measure both short- and long- term effects from
cosmic rays, see interactions of previously known image artifacts with starlight, and uncover several unexpected
systematics that affect photometric precision. Based on these results, we expect to attain Kepler's planned
photometric precision over 90% of the field of view.
Solar Planetary
ASPIICS: a giant coronagraph for the ESA/PROBA-3 Formation Flying Mission
Show abstract
Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the
external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades
the spatial resolution prevent useful observations of the white light corona inside typically 2-2.5 solar radii. Formation
flying offers an elegant solution to these limitations and allows conceiving giant, externally-occulted coronagraphs using
a two-component space system with the external occulter on one spacecraft and the optical instrument on the other
spacecraft at a distance of hundred meters. Such an instrument, ASPIICS (Association de Satellites Pour l'Imagerie et
l'Interférométrie de la Couronne Solaire), has just been selected by the European Space Agency (ESA) to fly (launch
expected in 2014) on its third PROBA (Project for On-Board Autonomy) mission of formation flying demonstration
which is presently in phase B. It will perform both high spatial resolution imaging of the solar corona as well as 2-
dimensional spectroscopy of several emission lines (in particular the forbidden line of FeXIV at 530.285 nm) from the
coronal base out to 3 solar radii. For this, it will use filters, polarisers and a solid Fabry-Perot interferometer ("étalon").
The classical design of an externally-occulted coronagraph is adapted to the formation flying configuration allowing the
detection of the very inner corona as close as 0.04-0.05 solar radii (40-50 arcsec) from the solar limb. By tuning the
position of the occulter spacecraft, it may even be possible to reach the chromosphere and the upper part of the spicules.
The narrow angle camera of the MPCS suite for the MarcoPolo ESA Mission: requirements and optical design solutions
Show abstract
Possible optical designs of a Narrow Angle Camera (NAC) suitable for being the high resolution channel of the
MarcoPolo Camera System for the MarcoPolo ESA mission are presented. The MarcoPolo mission objective is the
rendezvous with a Near Earth Asteroid in order to fully characterize the body, to land on the surface and to return to
Earth a sample of the asteroid soil. Science goals for the NAC are global mapping of the object, detailed investigations of
the surface at high spatial resolution (order of millimeters), and deep examination of possible landing sites from a close
distance.
The instrument has a 3"/pixel scale factor, corresponding to 80 mm/px at 5 km from the surface, on a 1.75° × 1.75° FoV;
imaging in 5 to 8 different spectral bands (panchromatic and broadband), in the range between 400 and 900 nm, is
foreseen. Since the target is an extended low contrast object, to avoid image contrast degradation, only off-axis
unobstructed optical layouts have been considered. Solutions with two mirrors plus a refractive corrector, or all-reflective
three mirrors ones, have been studied, both allowing to reach good aberration balancing over all the field of
view: the diffraction Ensquared Energy inside one pixel of the detector is of the order of 70%. To cope with the
hazardous radiation environment in which the spacecraft will be immersed in during the mission, all the glasses selected
for the design are rad-hard type.
Stray light performance of the long range reconnaissance imager (LORRI) on the New Horizons Mission
Show abstract
The LOng-Range Reconnaissance Imager (LORRI) is the high resolution imager for the New Horizons mission to the
Pluto system and the Kuiper Belt, which is the vast region of icy bodies extending roughly from 30 to 50 astronomical
units (AU). LORRI is a monolithic SiC, Ritchey-Chrétien telescope with a 20.8 cm diameter primary mirror and with an
0.29° field of view. The detector is a thinned, backside-illuminated charge-coupled device (CCD) operated in frame
transfer mode to obtain 1024 × 1024 pixel, panchromatic images over a bandpass of approximately 350 nm to 850 nm
with 4.96 μrad pixels. LORRI operated successfully at the New Horizons Jupiter encounter in Feb-Mar 2007 and made
challenging observations of faint sources, such as the Jovian rings within a few degrees of sunlit Jupiter and the
nightside of Io illuminated by Jupiter shine. Ambitious observations are planned at Pluto encounter including some with
LORRI pointed within 15° of the Sun. A unique program of inflight calibrations has measured LORRI's stray light
rejection using Jupiter and the Sun. The measured point source transmittance (PST) function for LORRI decreases from
145 on axis to 4×10-10 at 75° off-axis.
SPEX: the spectropolarimeter for planetary exploration
Show abstract
SPEX (Spectropolarimeter for Planetary EXploration) is an innovative, compact instrument for spectropolarimetry,
and in particular for detecting and characterizing aerosols in planetary atmospheres. With its ~1-liter volume
it is capable of full linear spectropolarimetry, without moving parts. The degree and angle of linear polarization
of the incoming light is encoded in a sinusoidal modulation of the intensity spectrum by an achromatic
quarter-wave retarder, an athermal multiple-order retarder and a polarizing beam-splitter in the entrance pupil.
A single intensity spectrum thus provides the spectral dependence of the degree and angle of linear polarization.
Polarimetry has proven to be an excellent tool to study microphysical properties (size, shape, composition) of
atmospheric particles. Such information is essential to better understand the weather and climate of a planet.
The current design of SPEX is tailored to study Martian dust and ice clouds from an orbiting platform: a compact
module with 9 entrance pupils to simultaneously measure intensity spectra from 400 to 800 nm, in different
directions along the flight direction (including two limb viewing directions). This way, both the intensity and
polarization scattering phase functions of dust and cloud particles within a ground pixel are sampled while flying
over it. We describe the optical and mechanical design of SPEX, and present performance simulations and initial
breadboard measurements. Several flight opportunities exist for SPEX throughout the solar system: in orbit
around Mars, Jupiter and its moons, Saturn and Titan, and the Earth.
GAIA
Gaia: 1,000 million stars with 100 CCD detectors
Show abstract
Gaia is the next space-astrometry mission of the European Space Agency, following up on the success of the Hipparcos
mission. With a focal plane containing more than 100 large-area CCD detectors, Gaia will survey the sky and repeatedly
observe the brightest 1,000 million (one billion) objects, down to 20th magnitude, during its 5-year nominal lifetime.
Gaia's science data will comprise absolute astrometry, broad-band photometry, and low-resolution spectro-photometry.
Medium-resolution spectroscopic data (resolving power 11,500) will be obtained for the brightest 150 million sources,
down to 17th magnitude. The extreme thermo-mechanical stability of the spacecraft, combined with the selection of the
L2 Lissajous point of the Sun-Earth/Moon system for operations, allows stellar parallaxes (distances) to be measured
with standard errors less than 10 micro-arcsecond (μas) for stars brighter than 13th magnitude, 20-30 μas for stars at 15th
magnitude, and around 300 μas at magnitude 20. Photometric standard errors are in the milli-magnitude regime. The
spectroscopic data will allow the measurement of radial velocities with errors at the level of 15 km s-1 at magnitude 17.
Gaia's primary science goal is to unravel the kinematical, dynamical, and chemical structure and evolution of the Milky
Way. In addition, Gaia's data will touch many other areas of research, for instance stellar physics, solar-system bodies,
fundamental physics, and exo-planets. The Gaia spacecraft is currently undergoing its critical design review (CDR).
With a launch foreseen in the second half of 2012, the final catalogue is expected in 2020. The science community in
Europe, organized in the Gaia Data Processing and Analysis Consortium (DPAC), is responsible for the processing of
the Gaia data. This formidable task is in full preparation. The calibration of the data presents exciting challenges, in
particular in the area of radiation-damage-induced charge-transfer inefficiency (CTI).
JDEM
Joint Dark Energy Mission optical design studies
Show abstract
We present the latest optical design concepts for the Joint Dark Energy Mission (JDEM). This mission will tightly
constrain the cosmological parameters describing the accelerating expansion of the universe. The current candidate
designs are based on extensive examination of the interplay of requirements for the leading techniques being considered
for space borne observation: Baryon Acoustic Oscillation (BAO), Type Ia Supernovae (SN), and gravitational Weak
Lensing (WL). All techniques require very large fields of view across the visible/near infrared spectrum; BAO uniquely
requires a moderate dispersion wide field spectroscopy capability. Weak lensing requires very good stability and
knowledge of the point spread function in order to enable detection of local variations in galaxy ellipticities caused by
the intervening dark matter. SN imaging spectroscopy should be done to high photometric signal to noise in order to
make best use of these 'standard candles.' We have studied medium class and smaller, "Probe" class implementations
enabling from one to three of these techniques. We describe two concepts that were submitted to the 2010 Astrophysics
Decadal review as well as current concepts.
Optical performance budgeting for JDEM weak-lensing measurements
Show abstract
Weak gravitational lensing of galaxies is a versatile probe of the distribution of gravitating matter, both visible and
invisible, and the influence of cosmological dark energy on that distribution for z<1.5. The weak lensing method is under
consideration as an element of NASA-DOE Joint Dark Energy Mission (JDEM). The measurements are challenging,
because of an ambitious goal for sensitivity to feeble gravitational shear and a competing goal for an extremely large
statistical sample of galaxies. This motivates an instrument design which has very few pixels across each galaxy image
and yet must extract galaxy shape information with very high precision and accuracy. This in turn places stiff
requirements on calibration during observations and on instrument stability. We present a tool for estimating the impact
of telescope and detector physics on the estimated lensing shear, in a way that permits us to propagate the instrument
performance allocations all the way to bias uncertainties in gravitational shear. This tool can be validated against
integrated modeling, and would allow powerful capability for system engineering trades.
Wide-field spectroscopy and imaging at two plate scales with a focal three mirror anastigmat
Show abstract
The key enabling element of the Joint Dark Energy Mission (JDEM)1,2,3 is a wide-field, high-magnification
mixed spectroscopic and imaging telescope intended to study dark energy via measurement of the expansion
history of the universe and the growth of large-scale structure. It is designed to provide tight constraints on
the equation of state of dark energy and test the validity of general relativity. Complementary observation of
Baryon Acoustic Oscillations (BAO), Type 1a Supernovae (SNe) and Gravitational Weak Lensing (WL) are
under consideration for the mission. The science goals of this mission call for a high-resolution imaging
survey and a spectroscopic survey of at least 10,000 square degrees. Signal to noise requirements of the
Baryon Acoustic Oscillation (BAO) survey favor a prism disperser with a λ • d θ /d λ of roughly 200 arcsec and a
coarse plate scale (~0.45arsec/pixel). The WL imaging survey seeks the shapes of galaxies, and therefore
prefers a finer plate scale of ~0.1-0.23 arcsec/pixel. Accommodation all of these goals may be accomplished
with an afocal telescope but the results of this study suggest that a focal telescope is also capable of achieving
these goals. Discussed herein are several novel prism concepts designed for use in a focal three mirror
anastigmat telescope (TMA). Multiple elements are used for aberration balancing and tailoring resolving
power over the observational band. Several options for simultaneous or staggered imaging and spectroscopy
as well as the required plate scale change with a focal TMA are presented.
Off-axis telescopes for dark energy investigations
Show abstract
It is well known that a telescope with an unobstructed circular pupil delivers a smaller diffraction pattern
than one centrally obstructed by its secondary mirror. Spaceborne dark energy investigations require
measuring targets over a wide range of redshifts, with the most distant galaxies being the reddest, faintest,
and smallest. For any given signal-to-noise (SNR) requirement, these highest redshift targets are the most
demanding in terms of mission cost (time, aperture, etc), not only because they are faint but also because
the diffraction pattern is largest at the longest wavelengths being observed. At the same time, a
telescope's field of view must be large -- the order of a square degree -- to survey the entire extragalactic
sky in reasonable time. The large field of view imposes a minimum requirement on the size of the
secondary mirror baffle. For a centrally obstructed telescope, an enlarged secondary mirror baffle further
enlarges the diffraction pattern. Previously published JDEM telescopes were centrally obstructed. Here,
we explore unobstructed telescope designs because these can have a nearly ideal Airy diffraction pattern,
avoiding both the central obstruction and the supporting spider legs, limited only by optical
manufacturing and alignment errors. They therefore can deliver the best possible SNR for a given
aperture. Simulations show that a 1.1m unobstructed aperture can deliver about the same cosmological
constraints as a 1.4m aperture that has a 50% linear central obstruction.
Euclid
The Euclid Mission
Show abstract
Euclid is a high precision survey mission under development by the European Space Agency to investigate the properties
of Dark Energy and Dark Matter by means of a weak lensing and baryon acoustic oscillations experiments. The technical
capabilities of Euclid are such that it also addresses other cosmological and astronomical topics, providing an unprecedented
science legacy. The survey mission will carry out an imaging and spectroscopic survey of the entire extragalactic
sky (20,000 deg2). Euclid carries a meter class telescope which feeds two instruments: a visible imager (VIS), a near-infrared
photometer combined with a medium resolution spectrometer (NISP). The two instruments have identical sized
field of views (0.5 deg2) and will operate simultaneously in step-and-stare mode. The nominal mission period is 5 years.
We describe the mission, the satellite, and the payload concepts, which we have adopted at the start of the definition
phase.
Euclid imaging channels: from science to system requirements
Show abstract
Euclid is an ESA Cosmic Vision wide-field space mission concept dedicated to the high-precision study of Dark Energy
and Dark Matter. The mission relies on two primary cosmological probes: Weak gravitational Lensing (WL) and Baryon
Acoustic Oscillations (BAO).
The first probe requires the measurement of the shape and photometric redshifts of distant galaxies. The second probe is
based on the 3-dimensional distribution of galaxies through spectroscopic redshifts. Additional cosmological probes are
also used and include cluster counts, redshift space distortions, the integrated Sachs-Wolfe effect (ISW) and galaxy
clustering, which can all be derived from a combination of imaging and spectroscopy.
Euclid Imaging Channels Instrument of the Euclid mission is designed to study the weak gravitational lensing
cosmological probe. The combined Visible and Near InfraRed imaging channels form the basis of the weak lensing
measurements. The VIS channel provides high-precision galaxy shape measurements for the measurement of weak
lensing shear. The NIP channel provides the deep NIR multi-band photometry necessary to derive the photometric
redshifts and thus a distance estimate for the lensed galaxies.
This paper describes the Imaging Channels design driver requirements to reach the challenging science goals and the
design that has been studied during the Cosmic Vision Assessment Phase.
VIS: the visible imager for Euclid
Show abstract
Euclid-VIS is a large format visible imager under investigation for the ESA Euclid space mission in their Cosmic Vision
program. Together with the near infrared photometer (NIP) it forms the basis of the weak lensing measurements of
Euclid. VIS will image in a single r+i+z band from 550-920 nm over a field of view of ~0.5 deg2. Over 4 exposures
totalling 1800 sec, VIS will reach to V=24.9 (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 PSF over a wide surcey area of of 20000 deg2
to measure the cosmic shear from over 2 billion galaxies to high levels of accuracy, from which the cosmological
parameters will be measured. In addition, VIS will also provide a legacy deep imaging dataset of unprecedented spatial
resolution over the entire extra-Galactic sky. Here we will present the results of the study carried out by the Euclid
Imaging Consortium during the Euclid Assessment Phase.
NIP: the near infrared imaging photometer for Euclid
Show abstract
The NIP is a near infrared imaging photometer that is currently under investigation for the Euclid space mission
in context of ESA's 2015 Cosmic Vision program. Together with the visible camera (VIS) it will form the basis of
the weak lensing measurements for Euclid. The NIP channel will perform photometric imaging in 3 near infrared
bands (Y, J, H) covering a wavelength range from ~ 0.9 to 2 μm over a field of view (FoV) of ~ 0.5 deg2. With
the required limiting point source magnitude of 24 mAB (5 sigma) the NIP channel will be used to determine
the photometric redshifts of over 2 billion galaxies collected over a wide survey area of 20 000 deg2. In addition
to the photometric measurements, the NIP channel will deliver unique near infrared (NIR) imaging data over
the entire extragalactic sky, enabling a wide variety of ancillary astrophysical and cosmological studies. In this
paper we will present the results of the study carried out by the Euclid Imaging Consortium (EIC) during the
Euclid assessment phase.
The E-NIS instrument on-board the ESA Euclid Dark Energy Mission: a general view after positive conclusion of the assessment phase
Show abstract
The Euclid Near-Infrared Spectrometer (E-NIS) Instrument was conceived as the spectroscopic probe on-board the ESA
Dark Energy Mission Euclid. Together with the Euclid Imaging Channel (EIC) in its Visible (VIS) and Near Infrared
(NIP) declinations, NIS formed part of the Euclid Mission Concept derived in assessment phase and submitted to the
Cosmic Vision Down-selection process from which emerged selected and with extremely high ranking. The Definition
phase, started a few months ago, is currently examining a substantial re-arrangement of the payload configuration due to
technical and programmatic aspects. This paper presents the general lines of the assessment phase payload concept on
which the positive down-selection judgments have been based.
Systems Concepts I
Definition phase activities for ESA's Cosmic Vision mission PLATO
Show abstract
PLATO - PLAnetary Transits and Oscillations of stars - is a Cosmic Vision 2015-2025 M-class mission candidate of
ESA's future Science and Robotic Exploration programme. The scientific goals are to detect exoplanetary transits and to
characterize the parent stars using astero-seismology. This is achieved through high-accuracy, high time-resolution
photometry in the visible waveband. Assessment studies were carried out for all M-class missions during 2008-2009 in
order to design a basic spacecraft configuration and identify critical areas. Following the down-selection in the beginning
of 2010, PLATO will enter into the Definition Phase, in which the spacecraft design will be consolidated and optimized.
The proposed payload will use a multi-aperture approach in which the combined observations of 34 telescopes with
individual pupil sizes of ~120 mm will produce highly accurate light curves of the target stars. Since the orbits of the
exoplanets should preferably be in or close to their habitable zone, an observation period of several years per sky field is
required to detect repeated transits of the exoplanets around the parent stars. This requires a stable spacecraft with a high
pointing accuracy and a benign operating environment. It is foreseen to launch PLATO using a Soyuz 2-1b via a direct
insertion into a large amplitude orbit around Sun-Earth L2. This paper will give an overview of the PLATO mission and
the planned activities during the Definition Phase.
A 4-meter wide field coronagraph space telescope for general astrophysics and exoplanet observations
Show abstract
The Wide Field Coronagraph Telescope (WFCT) is a 4-meter space telescope for general astrophysics and exoplanet
observations that meets the 2000 Decadal Committee requirements.
This paper presents a design for a 4-m diameter, off-axis space telescope that offers high performance in both wide field
and coronagraphic imaging modes. A 3.8 x 3.3-m unobstructed elliptical pupil is provided for direct coronagraphic
imaging of exoplanets and a 4-m diameter pupil for wide-field imaging from far-ultraviolet (UV) to near-infrared (IR).
The off-axis wide-field optics are all reflective and designed to deliver an average of 12 nm wavefront aberrations over a
6 x 24 arcminute field of view (FOV), therefore providing diffraction-limited images down to 300 nm wavelength and
15 mas images down to a wavelength limit set only by the mirror coatings. The coronagraph with phase-induced
amplitude apodization (PIAA) provides diffraction suppression around a 360-degree field with high Strehl and
sensitivity at the 1e-10 level to an inner working angle of 2 λ/D (or 50 mas at 500 nm wavelength).
This paper focuses on the optical design that allows the above imaging features to be combined in single telescope, and
gives a preliminary spacecraft design and costing, assuming a distant trailing orbit.
A space imaging concept based on a 4m structured spun-cast borosilicate monolithic primary mirror
Show abstract
Lockheed Martin Corporation (LMC) tasked The University of Arizona Steward Observatory (UASO) to conduct an
engineering study to examine the feasibility of creating a 4m space telescope based on mature borosilicate technology
developed at the UASO for ground-based telescopes. UASO has completed this study and concluded that existing launch
vehicles can deliver a 4m monolithic telescope system to a 500 km circular orbit and provide reliable imagery at NIIRS
7-8. An analysis of such an imager based on a lightweight, high-performance, structured 4m primary mirror cast from
borosilicate glass is described. The relatively high CTE of this glass is used to advantage by maintaining mirror shape
quality with a thermal figuring method. Placed in a 290 K thermal shroud (similar to the Hubble Space Telescope), the
orbit averaged figure surface error is 6nm rms when earth-looking. Space-looking optical performance shows that a
similar thermal conditioning scheme combined with a 270 K shroud achieves primary mirror distortion of 10 nm rms
surface. Analysis shows that a 3-point bipod mount will provide launch survivability with ample margin. The primary
mirror naturally maintains its shape at 1g allowing excellent end-to-end pre-launch testing with e.g. the LOTIS 6.5m
Collimator. The telescope includes simple systems to measure and correct mirror shape and alignment errors
incorporating technologies already proven on the LOTIS Collimator. We have sketched a notional earth-looking 4m
telescope concept combined with a wide field TMA concept into a DELTA IV or ATLAS 552 EELV fairing. We have
combined an initial analysis of launch and space performance of a special light-weighted honeycomb borosilicate mirror
(areal density 95 kg/m2) with public domain information on the existing launch vehicles.
A general purpose astronomy small satellite: an approach to low-cost space telescope design using space-qualified ground telescopes
Natasha Bosanac,
Sydney Do,
Hui Ying Wen,
et al.
Show abstract
The General Purpose Astronomy - Small Satellite (GPA-SS) project studied the feasibility of developing a useful space
telescope with a cost to launch below $100 million. An optical telescope assembly (OTA) designed for ground use is
proposed for use in a space mission in order to take advantage of the economies of scale in existing mirror fabrication
processes. This paper details the additional design, manufacture and test tasks required to flight-qualify the ground
telescope. A near-infrared imaging space telescope was costed as a potential mission. Key subsystems were designed at a
conceptual level. This design was used both to estimate subsystem costs and to inform the science achievable from a
given telescope design. Subsystem costs were estimated from the design through a combination of previously published
cost estimating relationships and vendor quotes. This paper concludes that the space-qualification of an existing ground
telescope is a potential approach for making significant cost savings when designing a low cost space telescope.
Additional work on design and cost estimation around the framework presented in this paper could be undertaken to add
certainty to the cost estimate.
WISH: wide-field imaging surveyor at high redshift
Toru Yamada,
Mamoru Doi,
Tomotsugu Goto,
et al.
Show abstract
WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe.
We will launch a 1.5m telescope equipped with 1000 arcmin2 wide-field NIR camera by late 2010's in order to conduct
unique ultra-deep and wide-area sky surveys at 1-5 micron. The primary science goal of WISH mission is pushing the
high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging capability and the dedicated
survey strategy. We expect to detect ~104 galaxies at z=8-9, ~3-6x103 galaxies at z=11-12, and ~50-100 galaxies at
z=14-17 within about 5 years of the planned mission life time. It is worth mentioning that a large fraction of these
objects may be bright enough for the spectroscopic observations with the extremely large telescopes. By adopting the optimized strategy for the recurrent observations to reach the depth, we also use the surveys to detect transient objects.
Type Ia Supernova cosmology is thus another important primary goal of WISH. A unique optical layout has been
developed to achieve the diffraction-limited imaging at 1-5micron over the required large area. Cooling the mirror and
telescope to ~100K is needed to achieve the zodiacal light limited imaging and WISH will achieve the required
temperature by passive cooling in the stable thermal environment at the orbit near Sun-Earth L2. We are conducting the
conceptual studies and development for the important components of WISH including the exchange mechanism for the
wide-field filters as well as the primary mirror fixation.
Systems Concepts II
Optical design of the EPIC-IM crossed Dragone telescope
Show abstract
The Experimental Probe of Inflationary Cosmology - Intermediate Mission (EPIC-IM) is a concept for the NASA
Einstein Inflation Probe satellite. EPIC-IM is designed to characterize the polarization properties of the Cosmic
Microwave Background to search for the B-mode polarization signal characteristic of gravitational waves generated
during the epoch of Inflation in the early universe. EPIC-IM employs a large focal plane with 11,000 detectors operating
in 9 wavelength bands to provide 30 times higher sensitivity than the currently operating Planck satellite. The optical
design is based on a wide-field 1.4 m crossed-Dragone telescope, an aperture that allows not only comprehensive
measurements of Inflationary B-mode polarization, but also measurements of the E-mode and lensing polarization
signals to cosmological limits, as well as all-sky maps of Galactic polarization with unmatched sensitivity and angular
resolution. The optics are critical to measuring these extremely faint polarization signals, and any design must meet
demanding requirements on systematic error control. We describe the EPIC-IM crossed Dragone optical design, its
polarization properties, and far-sidelobe response.
The Primordial Inflation Explorer (PIXIE) Mission
Show abstract
The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission to map the absolute intensity and linear
polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from
frequencies 30 GHz to 6 THz (1 cm to 50 μm wavelength). PIXIE uses a polarizing Michelson interferometer with 2.7 K
optics to measure the difference spectrum between two orthogonal linear polarizations from two co-aligned beams.
Either input can view either the sky or a temperature-controlled absolute reference blackbody calibrator. The multimoded
optics and high etendu provide sensitivity comparable to kilo-pixel focal plane arrays, but with greatly expanded
frequency coverage while using only 4 detectors total. PIXIE builds on the highly successful COBE/FIRAS design by
adding large-area polarization-sensitive detectors whose fully symmetric optics are maintained in thermal equilibrium
with the CMB. The highly symmetric nulled design provides redundant rejection of major sources of systematic
uncertainty. The principal science goal is the detection and characterization of linear polarization from an inflationary
epoch in the early universe, with tensor-to-scalar ratio r << 10-3. PIXIE will also return a rich data set constraining
physical processes ranging from Big Bang cosmology, reionization, and large-scale structure to the local interstellar
medium.
LEGOLAS: localizing evidence of gravitational waves by observations of light source astrometric signature
Show abstract
Improvement of our understanding of Fundamental Physics is more and more based on high precision measurements
over significant fractions of our Universe. Among the crucial tests of General Relativity and competing theories is the
detection of gravitational waves, which is the subject of advanced modern experiments (LISA, VIRGO, LIGO). Our
investigation is focused on a novel concept for pointed observations of selected astronomical objects in our Galaxy, like
compact binary systems, neutron stars and compact white dwarf binaries, which are expected to be sources of
gravitational waves in the Very Low Frequency range, i.e 10-4 Hz < fg < 10-1 Hz. The detection mechanism is based on
indirect astrometric observations by a spaceborne dedicated instrument, monitoring the astrometric light deflection of the
photons crossing the buffer zone of the gravitational source at the microarcsecond level accuracy. We discuss the class of
potential candidates, the mission concept and its high level specifications; furthermore, we present an implementation
concept including basic instrument characteristics (system configuration, telescope size and constraints, operating
wavelength, detector, operation).
Design of a four mirror astrometric telescope for light bending measurements
Show abstract
We present a new design of a four mirrors telescope for astrometric measurement to be used in the GAME
mission, currently under study at the Astronomical Observatory of Turin, Italy. The main aim of GAME -
Gamma Astrometric Measurement Experiment - is to measure the γ parameter of the Parameterized Post-
Newtonian formulation by looking at the deflection of light produced by the Sun's gravitational curvature, as in
the Dyson, Eddington et al. 1919 experiment, using a dedicated, space based dual-field telescope. A first design
has been presented in recent years, based on a Cassegrain scheme with a mask in front of the primary mirror to
realize multiple aperture Fizeau interferometry. The new design still implements a Fizeau interferometer, but the
telescope layout is based on a Korsch-like scheme with four conical mirrors, long focal length, and without the
use of exotic surfaces (aspheric or polynomial) as adopted in other long focal astrometric instruments. A different
combination scheme of the two lines of sight makes the dimensioning of the primary mirror more relaxed allowing
us to work with smaller surfaces and therefore to achieve a more compact payload configuration. The design
of the instrument and the masked interferometry approach allow us to maximize the astrometric performances
and at the same time to improve the baffling, minimizing the amount of stray light from the Sun. In this
paper we describe the mission profile, the observation principle, the new instrument layout and the expected
performances.
Achieving high-precision pointing on ExoplanetSat: initial feasibility analysis
Show abstract
ExoplanetSat is a proposed three-unit CubeSat designed to detect down to Earth-sized exoplanets in an orbit
out to the habitable zone of Sun-like stars via the transit method. To achieve the required photometric precision
to make these measurements, the target star must remain within the same fraction of a pixel, which is equivalent
to controlling the pointing of the satellite to the arcsecond level. The satellite will use a two-stage control
system: coarse control will be performed by a set of reaction wheels, desaturated by magnetic torque coils, and
fine control will be performed by a piezoelectric translation stage. Since no satellite of this size has previously
demonstrated this high level of pointing precision, a simulation has been developed to prove the feasibility of
realizing such a system.
The current baseline simulation has demonstrated the ability to hold the target star to within 0.05 pixels
or 1.8 arcseconds (with an 85 mm lens and 15 μm pixels), in the presence of large reaction wheel disturbances
as well as external environmental disturbances. This meets the current requirement of holding the target star
to 0.14 pixels or 5.0 arcseconds. Other high-risk aspects of the design have been analyzed such as the effect of
changing the guide star centroiding error, changing the CMOS sampling frequency, and reaction wheel selection
on the slew performance of the satellite. While these results are promising as an initial feasibility analysis,
further model improvements and hardware-in-the-loop tests are currently underway.
Systems Concepts III
System design of the compact IR space imaging system MIRIS
Show abstract
Multi-purpose Infra-Red Imaging System (MIRIS) is the main payload of the Korea Science and Technology Satellite-3
(STSAT-3), which is being developed by Korea Astronomy & Space Science Institute (KASI). MIRIS is a small space
telescope mainly for astronomical survey observations in the near infrared wavelengths of 0.9~2 μm. A compact wide
field (3.67 x 3.67 degree) optical design has been studied using a 256 x 256 Teledyne PICNIC FPA IR sensor with a
pixel scale of 51.6 arcsec. The passive cooling technique is applied to maintain telescope temperature below 200 K with
a cold shutter in the filter wheel for accurate dark calibration and to reach required sensitivity, and a micro stirling cooler
is employed to cool down the IR detector array below 100K in a cold box. The science mission of the MIRIS is to
survey the Galactic plane in the emission line of Paschen-α (Paα, 1.88 μ;m) and to detect the cosmic infrared background
(CIB) radiation. Comparing the Paα map with the Hα data from ground-based surveys, we can probe the origin of the
warm-ionized medium (WIM) of the Galaxy. The CIB is being suspected to be originated from the first generation stars
of the Universe and we will test this hypothesis by comparing the fluctuations in I (0.9~1.2 um) and H (1.2~2.0 um)
bands to search the red shifted Lyman cutoff signature. Recent progress of the MIRIS imaging system design will be
presented.
Optical design and performance of MIRIS near-infrared camera
Show abstract
Multi-purpose Infra-Red Imaging System (MIRIS) is a near-infrared camera onboard on the Korea Science and
Technology Satellite 3 (STSAT-3). The MIRIS is a wide-field (3.67° × 3.67°) infrared imaging system which employs a
fast (F/2) refractive optics with 80 mm diameter aperture. The MIRIS optics consists of five lenses, among which the
rear surface of the fifth lens is aspheric. By passive cooling on a Sun-synchronous orbit, the telescope will be cooled
down below 200 K in order to deliver the designed performance. As the fabrication and assembly should be carried out
at room temperature, however, we convert all the lens data of cold temperature to that of room temperature. The
sophisticated opto-mechanical design accommodates the effects of thermal contraction after the launch, and the optical
elements are protected by flexure structures from the shock (10 G) during the launch. The MIRIS incorporates the wide-band
filters, I (1.05 μm) and H (1.6 μm), for the Cosmic Infrared Background observations, and also the narrow-band
filters, Paα (1.876 μm) and a specially designed dual-band continuum, for the emission line mapping of the Galactic
interstellar medium. We present the optical design, fabrication of components, assembly procedure, and the performance
test results of the qualification model of MIRIS near-infrared camera.
Development of mechanical structure for the compact space IR camera MIRIS
Show abstract
MIRIS is a compact near-infrared camera with a wide field of view of 3.67°×3.67° in the Korea Science and
Technology Satellite 3 (STSAT-3). MIRIS will be launched warm and cool the telescope optics below 200K by pointing
to the deep space on Sun-synchronous orbit. In order to realize the passive cooling, the mechanical structure was
designed to consider thermal analysis results on orbit. Structural analysis was also conducted to ensure safety and
stability in launching environments. To achieve structural and thermal requirements, we fabricated the thermal shielding
parts such as Glass Fiber Reinforced Plastic (GFRP) pipe supports, a Winston cone baffle, aluminum-shield plates, a
sunshade, a radiator and 30 layers of Multi Layer Insulation (MLI). These structures prevent the heat load from the
spacecraft and the earth effectively, and maintain the temperature of the telescope optics within operating range. A micro
cooler was installed in a cold box including a PICNIC detector and a filter-wheel, and cooled the detector down to a
operating temperature range. We tested the passive cooling in the simulated space environment and confirmed that the
required temperature of telescope can be achieved. Driving mechanism of the filter-wheel and the cold box structure
were also developed for the compact space IR camera. Finally, we present the assembly procedures and the test result for
the mechanical parts of MIRIS.
The design and capabilities of the EXIST optical and infra-red telescope (IRT)
Show abstract
The Infra-Red Telescope is a critical element of the EXIST (Energetic X-Ray Imaging Survey Telescope) observatory.
The primary goal of the IRT is to obtain photometric and spectroscopic measurements of high redshift
(≥6) gamma ray reaching to the epoque of reionization. The photometric and spectral capabilities of the IRT
will allow to use GRB afterglow as probes of the composition and ionization state of the intergalactic medium
of the young universe. A prompt follow up (within three minutes) of the transient discovered by the EXIST
makes IRT a unique tool for detection and study of these events in the infrared and optical wavelength, which
is particularly valuable at wavelengths unavailable to the ground based observatories. We present the results of
the mission study development on the IRT as part of the EXIST observatory.
Actuated hybrid mirrors for space telescopes
Show abstract
This paper describes new, large, ultra-lightweight, replicated, actively controlled mirrors, for use in space telescopes.
These mirrors utilize SiC substrates, with embedded solid-state actuators, bonded to Nanolaminate metal foil reflective
surfaces. Called Actuated Hybrid Mirrors (AHMs), they use replication techniques for high optical quality as well as
rapid, low cost manufacturing. They enable an Active Optics space telescope architecture that uses periodic image-based
wavefront sensing and control to assure diffraction-limited performance, while relaxing optical system fabrication,
integration and test requirements.
Shape correction of thin mirrors in a reconfigurable modular space telescope
Show abstract
In order to facilitate the construction of future large space telescopes, the development of low cost, low mass
mirrors is necessary. However, such mirrors suffer from a lack of structural stability, stiffness, and shape accuracy.
Active materials and actuators can be used to alleviate this deficiency. For observations in the visible wavelengths,
the mirror surface must be controlled to an accuracy on the order of tens of nanometers. This paper presents
an exploration of several mirror design concepts and compares their effectiveness at providing accurate shape
control. The comparison test is the adjustment of a generic mirror from its manufactured spherical shape to the
shape required by various off-axis mirrors in a segmented primary mirror array. A study of thermal effects is
also presented and, from these results, a recommended design is chosen.
Minimizing actuator-induced errors in active space telescope mirrors
Show abstract
The trend in future space telescopes points toward increased primary mirror diameter, which improves resolution
and sensitivity. However, given the constraints on mass and volume deliverable to orbit by current launch
vehicles, creative design solutions are needed to enable increased mirror size while keeping mass and volume
within acceptable limits. Lightweight, segmented, rib-stiffened, actively controlled primary mirrors have emerged
as a potential solution. Embedded surface-parallel actuators can be used to change the mirror prescription onorbit,
lowering mirror mass overall by enabling lighter substrate materials such as silicon carbide (SiC) and
relaxing manufacturing constraints. However, the discrete nature of the actuators causes high spatial frequency
residual errors when commanding low-order prescription changes. A parameterized finite element model is used
to simulate actuator-induced residual error and investigate design solutions that mitigate this error source.
Judicious specification of mirror substrate geometry and actuator length is shown to reduce actuator-induced
residual while keeping areal density constant. Specifically, a sinusoidally-varying rib shaping function is found to
increase actuator influence functions and decrease residual. Likewise, longer actuators are found to offer reduced
residual. Other options for geometric shaping are discussed, such as rib-to-facesheet blending and the use of two
dimensional patch actuators.
Membrane photon sieve telescopes
Show abstract
We are investigating new technologies for creating ultra-large apertures (>20m) for space-based imagery. Our approach
has been to create diffractive primaries in flat membranes to be deployed from compact payloads. This research has led
us to the development of photon sieves in which millions of holes of a well-determined size are positioned over an
otherwise opaque background. High resolution focusing is obtained for transmitted light. We have analyzed the
theoretical performance of several types of photon sieves to improve both efficiency and bandwidth. We have also
created several prototype devices in both rigid and flexible substrates.
Systems Concepts IV
PLATO: detailed design of the telescope optical units
Show abstract
The project PLAnetary Transits and Oscillations of stars (PLATO) is one of the three medium class (M class) missions
selected in 2010 for definition study in the framework of the ESA Cosmic Vision 2015-2025 program. The main
scientific goals of PLATO are the i) discovery and study of extra-solar planetary systems, (including those hosting Earth-like
planets in their habitable zone) by means of planetary transits detection from space and radial velocity follow-up
from ground, and ii) the characterization of the hosting stars through seismic analysis, in order to determine with high
accuracy planetary masses and ages. According to the study made by the PLATO Payload Consortium (PPLC) during
the PLATO assessment phase, the scientific payload consists of 34 all refractive telescopes having small aperture (120
mm) and wide field of view (greater than 1000 degree2) observing over 0.5-1 micron wavelength band. The telescopes
are mounted on a common optical bench and are divided in four families with an overlapping line-of-sight in order to
maximize the science return. In this paper, we will describe the detailed design of the Telescope Optical Units (TOUs)
focusing on the selected optical configuration and the expected performances.
THESIS: the terrestrial habitable-zone exoplanet spectroscopy infrared spacecraft
Show abstract
THESIS, the Transiting Habitable-zone Exoplanet Spectroscopy Infrared Spacecraft, is a concept for a medium/Probe
class exoplanet mission. Building on the recent Spitzer successes in exoplanet characterization, THESIS would extend
these types of measurements to super-Earth-like planets. A strength of the THESIS concept is simplicity, low technical
risk, and modest cost. The mission concept has the potential to dramatically advance our understanding of conditions on
extrasolar worlds and could serve as a stepping stone to more ambitious future missions. We envision this mission as a
joint US-European effort with science objectives that resonate with both the traditional astronomy and planetary science
communities.
See-coast: polarimetric and spectral characterization of exoplanets with a small space telescope
Show abstract
To characterize orbits and atmospheres of exoplanets with large orbits (≥ a few AU), direct imaging is nowadays
the sole way. From space, this involves high contrast imaging techniques as coronagraphy, differential imaging or
wavefront control. Several methods exist or are under development and several small (~1.5m) space telescope
missions are proposed. One of them is See-coast (super-Earth explorer coronagraphic off-axis space telescope)
which will be proposed to the next ESA Cosmic Vision call. It will provide polarimetric and spectral characterization
of giant gazeous planets and possibly Super-Earths in visible light. In this paper, we first detail science
cases of this mission. We then describe the foreseen telescope design and its instrumentation. We finally derive
performance for a particular instrumental configuration from numerical simulation and we show how See-coast
can retrieve planet spectra.
ExoplanetSat: detecting transiting exoplanets using a low-cost CubeSat platform
Show abstract
Nanosatellites, i.e. spacecraft that weigh between 1 and 10 kg, are drawing increasing interest as platforms
for conducting on-orbit science. This trend is primarily driven by the ability to piggyback nanosatellites on
the launch of large spacecraft and hence achieve orbit at greatly reduced cost. The CubeSat platform is a
standardized nanosatellite configuration, consisting of one, two, or three 10 cm x 10 cm x 10 cm units (1, 2,
or 3 "U"s) arranged in a row. We present a CubeSat-based concept for the discovery of transiting exoplanets
around the nearest and brightest Sun-like stars. The spacecraft prototype - termed ExoplanetSat - is a 3U space
telescope capable of monitoring a single target star from low Earth orbit. Given the volume limitations of
the CubeSat form factor, designing a capable spacecraft requires overcoming significant challenges. This work
presents the initial satellite configuration along with several subsystem-specific solutions to the aforementioned
constraints. An optical design based on a modified commercial off-the-shelf camera lens is given. We also
describe a novel two-stage attitude control architecture that combines 3-axis reaction wheels for coarse pointing
with a piezoelectric translation stage at the focal plane for fine pointing. Modeling and simulation results are
used to demonstrate feasibility by quantifying ExoplanetSat pointing precision, signal-to-noise ratio, guide star
magnitude, and additional design parameters which determine system performance.
TPF Coronagraph
ACCESS: a concept study for the direct imaging and spectroscopy of exoplanetary systems
Show abstract
ACCESS is one of four medium-class mission concepts selected for study in 2008-9 by NASA's Astrophysics Strategic
Mission Concepts Study program. ACCESS evaluates a space observatory designed for extreme high-contrast imaging
and spectroscopy of exoplanetary systems. An actively-corrected coronagraph is used to suppress the glare of diffracted
and scattered starlight to contrast levels required for exoplanet imaging. The ACCESS study considered the relative
merits and readiness of four major coronagraph types, and modeled their performance with a NASA medium-class space
telescope. The ACCESS study asks: What is the most capable medium-class coronagraphic mission that is possible with
telescope, instrument, and spacecraft technologies available today? Using demonstrated high-TRL technologies, the
ACCESS science program surveys the nearest 120+ AFGK stars for exoplanet systems, and surveys the majority of
those for exozodiacal dust to the level of 1 zodi at 3 AU. Coronagraph technology developments in the coming year are
expected to further enhance the science reach of the ACCESS mission concept.
The pupil mapping exoplanet coronagraphic observer (PECO)
Show abstract
The Pupil-mapping Exoplanet Coronagraphic Observer (PECO) mission concept is a 1.4-m space-based coronagraphic telescope optimized to image exoplanets and disks at optical wavelengths and characterize them through low resolution spectroscopy and polarimetry. Thanks to a high efficiency Phase-Induced Amplitude Apodization (PIAA) coronagraph, PECO can deliver 1e-10 contrast at 2 λ/D separation (0.15") with no loss in angular resolution or throughput due to the coronagraph. PECO acquires narrow field images simultaneously in 16 spectral bands over wavelengths from 0.4 to 0.9 μm , utilizing all available photons for maximum wavefront sensing efficiency and optimal sensitivity for imaging and spectroscopy. PECO can detect and characterize potentially habitable planets around 20 known F, G, K type stars, and map exozodiacal clouds to a fraction of our own own zodiacal dust content.
PECO's key technologies are currently under active development at several testbeds, and will enable efficient exoplanet imaging missions across a wide range of telescope sizes, from a sub-meter debris disk and giant planet imager to a ~4-m life-finding mission.
Optical design of dilute aperture visible nulling coronagraph imaging (DAViNCI)
Show abstract
This paper presents the optical design of the Dilute Aperture Visible Nulling Coronagraph Imaging (DAViNCI).
DAViNCI's dilute aperture approach to the TPF-C extra-solar earth-like detection mission reduces cost and technical
risk compared to other filled aperture approaches. DAViNCI has been studied in an ASMCS (Astrophysics Strategic
Mission Concept Study) and is included within the ASTRO2010 Decadal review [1]. The DAViNCI team is led by
Michael Shao (PI) of JPL.
Visible nulling coronagraphy testbed development for exoplanet detection
Show abstract
Three of the recently completed NASA Astrophysics Strategic Mission Concept (ASMC) studies addressed the
feasibility of using a Visible Nulling Coronagraph (VNC) as the prime instrument for exoplanet science. The VNC
approach is one of the few approaches that works with filled, segmented and sparse or diluted aperture telescope systems
and thus spans the space of potential ASMC exoplanet missions. NASA/Goddard Space Flight Center (GSFC) has a
well-established effort to develop VNC technologies and has developed an incremental sequence of VNC testbeds to
advance the this approach and the technologies associated with it. Herein we report on the continued development of the
vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates
under high bandwidth closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence
of three visible light nulling milestones of sequentially higher contrasts of 108, 109 and 1010 at an inner working angle of
2*λ/D and ultimately culminate in spectrally broadband (>20%) high contrast imaging. Each of the milestones, one per
year, is traceable to one or more of the ASMC studies. The VNT uses a modified Mach-Zehnder nulling interferometer,
modified with a modified "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent
fiber bundle and achromatic phase shifters. Discussed will be the optical configuration laboratory results, critical
technologies and the null sensing and control approach.
Single aperture imaging astrometry with a diffracting pupil: application to exoplanet mass measurement with a small coronagraphic space telescope
Show abstract
High precision astrometry of nearby bright stars is theoretically (in the photon noise limit) possible with a space coronagraph using a wide field diffraction limited camera imaging an annulus of background stars around the central coronagraphic field. With the sub-micro arcsecond accuracy theoretically achievable on a 1.4-m telescope, the mass of all planets that can be imaged by the coronagraph would be estimated. Simultaneous imaging and astrometric measurements would reduce the number of astrometric measurements necessary for mass determination, and reduce confusion between multiple planets and possible exozodiacal clouds in the coronagraphic image. While scientifically attractive, this measurement is technically very challenging, and must overcome astrometric distortions, which, in conventional telescopes, are several orders of magnitude above the photon noise limit. In this paper, we propose a new approach to calibrating astrometric distortions in the wide field imaging camera. The astrometric measurement is performed by simultaneously imaging background stars and diffraction spikes from the much brighter coronagraphic target on the same focal plane array. The diffraction spikes are generated by a series of small dark spots on the primary mirror to reduce sensitivity to optical and mechanical distortions. Small scale distortions and detector errors are averaged down to sub-micro arcsecond by rolling the telescope around the line of sight. A preliminary error budget is shown and discussed to identify major sources of error for a 1.4-m telescope imaging a 0.25 squaredeg field of view at the galactic pole.
Laboratory demonstration of high-contrast imaging at 2 l/D on a temperature-stabilized testbed in air
Show abstract
Direct imaging of extrasolar planets in visible light, and Earth-like planets in particular, is an exciting but difficult problem requiring a telescope imaging system with 10-10 contrast at separations of 100mas and less. Furthermore, only a small 1-2m space telescope may be realistic for a mission in the foreseeable future, which puts strong demands on the performance of the imaging instrument. Fortunately, an efficient coronagraph called the Phase Induced Amplitude Apodization (PIAA) coronagraph may enable Earth-like planet imaging for such small telescopes if any exist around the nearest stars. In this paper, we report on the latest results from a testbed at the NASA Ames Research Center focused on testing the PIAA coronagraph. This laboratory facility was built in 2008 and is designed to be flexible, operated in a highly stabilized air environment, and to complement efforts at NASA JPL's High Contrast Imaging Testbed. For our wavefront control we are focusing on using small Micro-Electro-Mechanical-System deformable mirrors (MEMS DMs), which promises to reduce the size of the beam and overall instrument, a consideration that becomes very important for small telescopes. In this paper, we briefly describe our lab and methods, including the new active thermal control system, and report the demonstration of 5.4×10-8 average raw contrast in a dark zone from 2.0 - 5.2 λ/D. In addition, we present an analysis of our current limits and solutions to overcome them.
TPF Occulter
New Worlds Probe
Show abstract
The New Worlds Observer is a flagship-scale terrestrial planet finding and characterizing mission using an external
occulter known as a starshade. The starshade is a separate space vehicle from the observing telescope; the starshade
performs all the necessary starlight suppression to enable high contrast imaging of terrestrial exo-planets. While effective
as a flagship-scale mission designed to fulfill and exceed the requirements of the Terrestrial Planet Finder (TPF) mission,
the starshade architecture is flexible and can accommodate a variety of design and cost categories, including working
with an existing telescope. We present in this paper an architecture using a starshade with the James Web Space
Telescope (JWST), a mission concept we call New Worlds Probe, which can deliver many of the TPF mission
requirements for significantly lower mission cost. We give an overview of the science capabilities, the starshade design
and technical maturity, and concepts for starshade-JWST cooperative operation.
Broadband suppression and occulter position sensing at the Princeton occulter testbed
Show abstract
The Princeton occulter testbed uses long-distance propagation with a diverging beam and an optimized
occulter mask to simulate the performance of external occulters for finding extrasolar planets. We present
new results from the testbed in both monochromatic and broadband light. In addition, we examine sensing
and control of occulter position using out-of-band spectral leak around the occulter and occulter position
tolerancing. These results are validated by numerical simulations of propagation through the system.
Error budgeting and tolerancing of starshades for exoplanet detection
Show abstract
A flower-like starshade positioned between a star and a space telescope is an attractive option for blocking the starlight
to reveal the faint reflected light of an orbiting Earth-like planet. Planet light passes around the petals and directly enters
the telescope where it is seen along with a background of scattered light due to starshade imperfections. We list the
major perturbations that are expected to impact the performance of a starshade system and show that independent models
at NGAS and JPL yield nearly identical optical sensitivities. We give the major sensitivities in the image plane for a
design consisting of a 34-m diameter starshade, and a 2-m diameter telescope separated by 39,000 km, operating
between 0.25 and 0.55 um. These sensitivities include individual petal and global shape terms evaluated at the inner
working angle. Following a discussion of the combination of individual perturbation terms, we then present an error
budget that is consistent with detection of an Earth-like planet 26 magnitudes fainter than its host star.
Occulting ozone observatory science overview
Show abstract
We present an analysis of the Occulting Ozone Observatory (O3) - a $1 billion class mission dedicated to finding
extra-solar planets down to Earth size, performing photometric characterizations of planets and disks, detecting
the presence of ozone, and general astrophysics. We present trade studies for the observatory, composed of a 1
to 2 m telescope based on heritage imaging systems and a complementary sized, free-flying occulter spacecraft,
to maximize the expected science yield for this mission class. Using a camera with four filters each in the 250-
550 nm and 500-1100 nm bands, this modest-size telescope can detect atmospheric ozone in Earth-like planets,
methane in gas giants, determine planetary spin rotation periods, characterize the surface composition of rocky
planets and determine or constrain the values of basic orbital elements. We present multiple different mission
designs along with the expected number of planetary detections and photometric characterizations.
Direct imaging and spectroscopy of habitable planets using JWST and a starshade
Show abstract
A starshade with the James Webb Space Telescope (JWST) is the only possible path forward in the next
decade to obtain images and spectra of a planet similar to the Earth, to study its habitability, and search for
signs of alien life. While JWST was not specifically designed to observe using a starshade, its near-infrared
instrumentation is in principle capable of doing so and could achieve major results in the study of terrestrialmass
exoplanets. However, because of technical reasons associated with broadband starlight suppression and
filter red-leak, NIRSpec would need a slight modification to one of its target acquisition filters to enable feasible
observations of Earth-like planets. This upgrade would 1) retire the high risk associated with the effects of the
current filter red leak which are difficult to model given the current state of knowledge on instrument stray light
and line spread function at large separation angles, 2) enable access to the oxygen band at 0.76 μm in addition
to the 1.26 μm band, 3) enable a smaller starshade by relaxing requirements on bandwidth and suppression 4)
reduce detector saturation and associated long recovery times. The new filter would not affect neither NIRSpecs
scientific performance nor its operations, but it would dramatically reduce the risk of adding a starshade to JWST
in the future and enhance the performance of any starshade that is built. In combination with a starshade, JWST
could be the most capable and cost effective of all the exoplanet hunting missions proposed for the next decade,
including purpose built observatories for medium-size missions.
Alternative starshade missions
Show abstract
Starshades have been shown to hold the potential to reveal Earth-like planets around nearby stars and to allow detailed
follow-up study including spectroscopy. Ideally this would be performed with a starshade in excess of 50m diameter and
a telescope over 4m in diameter. However, such a flagship-class mission is unlikely to be realized in under fifteen years.
But much can be accomplished in substantially less expensive missions. I will review the alternatives and provide an
assessment of various architectures and what they can accomplish. These alternatives will include using JWST as the
telescope, using small dedicated telescopes, and using smaller starshades.
ATLAST
Science drivers and requirements for an Advanced Technology Large Aperture Space Telescope (ATLAST): implications for technology development and synergies with other future facilities
Show abstract
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR
space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at
the forefront of modern astronphysics, including "Is there life elsewhere in the Galaxy?" We present a range of science
drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction
limited imaging at 0.5 μm wavelength, minimum collecting area of 45 square meters, high sensitivity to light
wavelengths from 0.1 μm to 2.4 μm, high stability in wavefront sensing and control). We will also discuss the synergy
between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology
development that will enable the construction for a cost that is comparable to current generation observatory-class space
missions.
Comparative concepts for ATLAST optical designs
Show abstract
The ATALST (Advanced Technology for Large Aperture Space Telescopes) effort has presented several design
incarnations. Here we will compare the design and performance of the 9.2m segmented, the 8m monolithic on-axis and
8m x 6m off-axis concepts.
ATLAST-9.2m: a large-aperture deployable space telescope
Show abstract
We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope
(ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36
hexagonal 1.315 m (flat-to-flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing
it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch
Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing
and control, pointing and thermal control, and in-space servicing options.
ATLAST-8 Mission concept study for 8-meter monolithic UV/optical space telescope
Show abstract
ATLAST-8m is an 8-meter monolithic UV/optical/NIR space observatory which could be placed in orbit at Sun-Earth
L2 by a heavily lift launch vehicle. Two development study cycles have resulted in a detailed concept including a dual
foci optical design; several primary mirror launch support and secondary mirror support structural designs; spacecraft
propulsion, power and pointing control design; and thermal design. ATLAST-8m is designed to yield never before
achieved performance to obtain fundamental astronomical breakthroughs.
Late Breaking News
The potential of small space telescopes for exoplanet observations
Show abstract
The imaging of faint exoplanets near bright stars requires the development of very high contrast detection techniques,
including both precise wavefront control and deep starlight rejection. A system-level proof-of-principle experiment
carried out at at the Palomar Observatory has recently demonstrated that exoplanets can be detected very near stars even
with a fairly small (1.5 m diameter) telescope aperture, such as someday might be used by a first space-based exoplanet
imaging mission. Using fine-scale wavefront correction across this small aperture, together with fine pointing and focus
control, pre- and post-detection speckle reduction, and a vector vortex coronagraph, it has been possible to achieve
extremely good starlight rejection within a small number of diffractions beams of the stellar position. This performance
has recently allowed the imaging of the three HR8799 planets and the HD32297 disk, thus providing a first system-level
validation of the steps needed to achieve high-contrast observations at very small angles. These results thus serve to
highlight the potential of small space telescopes aiming at high-contrast exoplanet observations. Specifically, a small-angle
coronagraph enables the use of smaller telescopes, thus potentially reducing mission cost significantly.
Poster Session: AKARI
AKARI infrared bright source catalogues
Show abstract
Bright source catalogues based on the new mid- and far-infrared all-sky survey by the infrared astronomical
satellite AKARI were released into the public domain in March 2010. The mid-infrared catalogue contains
more than 870 thousand sources observed at 9 and 18 μm, and the far-infrared catalogue provides information
of about 427 thousand sources at 65, 90, 140, and 160 μm. The AKARI catalogues will take over the IRAS
catalogues and will become one of the most important catalogues in astronomy. We present the characteristics
of the AKARI infrared source catalogues as well as current activity for the future versions.
Poster Session: ATLAST
Spacecraft conceptual design for the 8-meter Advanced Technology Large Aperture Space Telescope (ATLAST)
Randall C. Hopkins,
Peter Capizzo,
Sharon Fincher,
et al.
Show abstract
The Advanced Concepts Office at Marshall Space Flight Center completed a brief spacecraft design study for the 8-
meter monolithic Advanced Technology Large Aperture Space Telescope (ATLAST-8m). This spacecraft concept
provides all power, communication, telemetry, avionics, guidance and control, and thermal control for the observatory,
and inserts the observatory into a halo orbit about the second Sun-Earth Lagrange point. The multidisciplinary design
team created a simple spacecraft design that enables component and science instrument servicing, employs articulating
solar panels for help with momentum management, and provides precise pointing control while at the same time fast
slewing for the observatory.
Thermal analysis of the Advanced Technology Large Aperture Space Telescope (ATLAST) 8-meter primary mirror
Show abstract
The Advanced Technology Large Aperture Space Telescope (ATLAST) preliminary design concept consists of an 8
meter diameter monolithic primary mirror enclosed in an insulated, optical tube with stray light baffles and a sunshade.
ATLAST will be placed in orbit about the Sun-Earth L2 point and will experience constant exposure to the sun. The
insulation on the optical tube and sunshade serve to cold bias the telescope which helps to minimize thermal gradients.
The objective is to maintain the primary mirror at 280K with an active thermal control system.
The geometric model of the primary mirror, optical tube, sun baffles, and sunshade was developed using Thermal
Desktop®1. A detailed model of the primary mirror was required in order to characterize the static performance and
thermal stability of the mirror during maneuvers. This is important because long exposure observations, such as extra-solar
terrestrial planet finding and characterization, require a very stable observatory wave front. Steady state thermal
analyses served to predict mirror temperatures for several different sun angles. Transient analyses were performed in
order to predict thermal time constant of the primary mirror for a 20 degree slew and a 30 degree roll maneuver.
This paper describes the thermal model and provides details of the geometry, thermo-optical properties, and the solar
environment that influences the thermal performance. All assumptions that were used in the analysis are also
documented. Estimates of mirror heater power requirements are reported. The thermal model is used to predict gradients
across and through the primary mirror using an idealized boundary temperature on the back and sides of the mirror of
280 K.
Coronagraphic wavefront control for the ATLAST 9.2m telescope
Show abstract
The Advanced Technology for Large Aperture Space Telescope (ATLAST) concept was assessed as one of the NASA
Astrophysics Strategic Mission Concepts (ASMC) studies. Herein we discuss the 9.2-meter diameter segmented aperture
version and its wavefront sensing and control (WFSC) with regards to coronagraphic detection and spectroscopic
characterization of exoplanets. The WFSC would consist of at least two levels of sensing and control: (i) an outer coarser
level of sensing and control to phase and control the segments and secondary mirror in a manner similar to the James
Webb Space Telescope but operating at higher temporal bandwidth, and (ii) an inner, coronagraphic instrument based,
fine level of sensing and control for both amplitude and wavefront errors operating at higher temporal bandwidths. The
outer loop would control rigid-body actuators on the primary and secondary mirrors while the inner loop would control
one or more segmented deformable mirror to suppress the starlight within the coronagraphic field-of-view. Herein we
discuss the visible nulling coronagraph (VNC) and the requirements it levies on wavefront sensing and control and show
the results of closed-loop simulations to assess performance and evaluate the trade space of system level stability versus
control bandwidth.
Poster Session: Euclid
Euclid ENIS spectrograph focal-plane design
Show abstract
The ENIS wide-field spectrograph is part of the instrument package on board of the European space mission Euclid
devoted to map the dark universe and proposed for launch in 2017. ENIS will operate in the near-IR spectral region
(0.8-2 μm) and will provide in 4-5 years an accurate and extremely large survey of cosmological redshifts. The
instrument focal-plane is based on a combination of state of the art detectors light fed by a slitless spectrograph
allowing coverage and analysis of a high number of targets per cycle. During the feasibility study a spectrograph
option based on Digital Micromirror Device (DMD) programmable slits, allowing a significant increase in
instrumental sensitivity and accuracy, has also been examined. ENIS has been recently (Feb this year) pre-selected
for a phase-A study within a group of three medium class missions; final selection is foreseen for the end of next
year after a new phase of instrument revision.
A description of the work done during the feasibility-study phase for the ENIS focal-plane is here presented.
A frame simulator for data produced by multi-accumulation readout detectors
Show abstract
A simulator of data frames produced by 'multi-accumulation' readout detectors has been developed during the feasibility
study for the NIS spectrograph, part of the European Euclid mission. The software can emulate various readout
strategies, allowing to compare the efficiency of different sampling techniques. Special care is given to two crucial
aspects: the minimization of the noise and the effects produced by cosmic hits.
The resulting readout noise is analyzed as a function of the background sources, detector native characteristics and
readout strategy, while the image deterioration by cosmic rays covers the simulation of hits and their correction
efficiency varying the readout modalities.
Simulated "multi-accumulation" frames, typical of multiplexer based detectors, are an ideal tool for testing the
efficiency of cosmic ray rejection techniques. In the present case cosmic rays are added to each raw frame conforming to
the rates and energy expected in the operational L2 region and in the chosen exposure time. Procedures efficiency for
cosmic ray identification and correction can also be easily tested in terms of memory occupancy and telemetry rates.
The Euclid near-infrared calibration source
Show abstract
The Euclid dark energy mission is currently competing in ESA's Cosmic Vision program. Its imaging instrument,
which has one visible and one infrared channel, will survey the entire extragalactic sky during the 5 year mission.
The near-infrared imaging photometer (NIP) channel, operating in the ~0.92 - 2.0 μm spectral range, will be
used in conjunction with the visible imaging channel (VIS) to constrain the nature of dark energy and dark
matter. To meet the stringent overall photometric requirement, the NIP channel requires a dedicated on-board
flat-field source to calibrate the large, 18 detector focal plane.
In the baseline concept a 170 mm Spectralon diffuser plate, mounted to a pre-existing shutter mechanism
outside the channel, is used as a flat-field calibration target, negating the need for an additional single-point-failure
mechanism. The 117 × 230 mm focal plane will therefore be illuminated through all of the channel's
optical elements and will allow flat-field measurements to be taken in all wavelength bands. A ring of low power
tungsten lamps, with custom reflecting elements optimized for optical performance, will be used to illuminate
the diffuser plate.
This paper details the end-to-end optical simulations of this concept, a potential mechanical implementation
and the initial tests of the proposed key components.
The data handling unit of the Euclid imaging channels: from the observational requirements to the unit architecture
Show abstract
The Euclid Imaging Channels Instrument of the Euclid mission is designed to study the weak gravitational lensing
cosmological probe. The combined Visible and Near Infrared imaging channels will be controlled by a common data
handling unit (PDHU), implementing onboard the instrument digital interfaces to the satellite. The PDHU main
functionalities include the scientific data acquisition and compression, the instrument commanding and control and the
instrument health monitoring. Given the high data rate and the compression needs, an innovative architecture, based on
the use of several computing and interface modules, considered as building blocks of a modular design will be presented.
The ground support equipment for the E-NIS instrument on-board the ESA-Euclid Dark Energy Mission in the baseline configuration presented in phase A
Show abstract
Euclid is a high-precision survey mission to map the geometry of the Dark Universe. The Euclid Mission concept
presented in the Assessment Phase Study Report1 was selected by ESA on February 2010 to undergo a competitive
Definition Phase. Euclid is a candidate for launch in the first slice of the Cosmic Vision Plan (M1/M2), with a possible
launch date of 2018. In this paper we refer to the instrument baseline configuration identified in the Assessment Phase. It
consisted of a Korsch telescope with a primary mirror of 1.2 m diameter and a focal plane hosting 3 scientific
instruments, each with a field of view of 0.5 deg2: (1) E-VIS: a CCD based optical imaging channel, (2) E-NIP: a NIR
imaging photometry channel, and (3) E-NIS: a NIR slitless spectral channel. We present the conceptual design developed
in the Assessment Phase study for the Ground Support Equipment required to support the assembly, integration and
verification operations at instrument level for the E-NIS baseline configuration, with particular regards to the scientific
and calibration activities.
EUCLID: design of the prism DMD NIR spectrograph
Show abstract
EUCLID, the ESA Dark Energy Mission, contains a NIR and a visible imagers (NIP & VIS), and an NIR spectrograph
(NIS). Different designs of the NIS have been studied especially a slitless design, a Digital Micromirror Device (DMD)
design using grisms and another using prisms, and more recently a combination of the NIP and NIS into one instrument.
We present the design of the prism DMD NIS. This design has the advantage over the slitless design of having a DMD
mask which reduces the background by a factor of more than 100 and all the advantages over the grism DMD NIS that a
prism gives over a grism as a higher and more uniform transmission, the absence of parasite orders, and a choice of the
slope of the spectral resolution with wavelength. The field per spectrograph was made sufficiently large to reduce the
number of spectrographs to two. The design was made so that the mapping of the sky of the NIS is easily compatible
with the mapping strategy of the NIP and VIS. Two designs were made. In one, the field is larger but the surface shapes
of the optics are complex which makes manufacturing more challenging. In the other, the design was made to be fully
compatible with the manufacturing criteria of SESO after extensive discussions to carefully understand the
manufacturing limitations especially the formula for highly aspheric surface shapes as biconics. This was done by
directly integrating the criteria into the optimization process of ZEMAX. A calibration system that uses the DMD with
the micromirrors in their OFF positions was also developed.
Opto-mechanical design of a DMD multislit spectrograph for the ESA Euclid Mission
Show abstract
The Euclid mission proposed in the context of the ESA Cosmic Vision program is aimed to study the challenging
problem of the Dark Energy, responsible of the acceleration of the Universe. One of the three probes of Euclid is
dedicated to study the Baryonic Acoustic Oscillations by means of spectroscopic observations of millions of galaxies in
the Near Infrared. One option for the Euclid Near Infrared Spectrograph (ENIS) is a multi-slit approach based on Digital
Micromirror Device (DMD) used as reconfigurable slit mask. The Texas Instrument 2048*1080 DMD with 13.68
micrometers pitch has been chosen. ENIS optical design is composed of four arms each using one DMD to cover a total
FOV of 0.48 square degree. The fore-optic design has to cope with the difficult task of having simultaneously a fast
beam (F/2.7) and a quasi-diffraction limited image on a 24 deg tilted plane. The compact three mirrors spectrograph is
using a grism in convergent beam for simplicity and compactness purposes. From the optical design, the mechanical
structure is based on a common carbon honeycomb bench to reach the challenging requirements of volume and mass.
Space evaluation of 2048x1080 mirrors DMD chip for ESA's EUCLID Mission
Show abstract
Next-generation infrared astronomical instrumentation for ground-based and space telescopes could be based on
MOEMS programmable slit masks for multi-object spectroscopy (MOS). This astronomical technique is used
extensively to investigate the formation and evolution of galaxies.
We are engaged in an ESA study for a technical assessment of using a DMD from Texas Instruments for space
applications (for example in ESA EUCLID mission). The DMD features 2048×1080 mirrors on a 13.68μm pitch,
where each mirror can be independently switched between an ON (+12°) position and an OFF (-12°) position. For MOS
applications in space, the device should work in vacuum, at low temperature, and each MOS exposure would last for
typically 1500s with micromirrors held in a static state (either ON or OFF). A specific thermal/vacuum test chamber has
been developed for test conditions down to -40°C at 10-5 mbar vacuum. Imaging capability for resolving each
micromirror has also been developed for determining degradation in any single mirror. Our first tests reveal that the
DMD remains fully operational at -40°C and in vacuum. A 1038 hours life test in space conditions, Total Ionizing Dose
radiation, thermal cycling and vibrations/shocks have also been successfully completed. These results do not reveal any
concerns regarding the ability of the DMD to meet environmental space requirements.
We have also developed a bench for MOS demonstration using MOEMS devices. DMD chip has been successfully
tested revealing good contrast values as well as good functionality for applying any mask pattern, demonstrating its full
ability for space instrumentation, especially in multi-object spectroscopy applications.
Poster Session: GAIA
Astrometric instrument model software tool for Gaia data reduction: challenges and implementation
Show abstract
The Astrometric Instrument Model system comprises several monitoring and diagnostic tasks for the astrometric
instrument aboard Gaia. It is a hierarchy of dedicated software modules aimed at decreasing the parameter degeneration
of the relation linking the observations to the instrumental behavior, and optimize the estimation process at the CCD and
field-of-view crossing level. Critical for the system is the definition and maintenance of a physical instrument model
fitting the science data, and able to accommodate non nominal configurations. Precise modeling of the astrometric
response is required for optimal definition of the data reduction and calibration algorithms, and to ensure high sensitivity
to both instrumental and astrophysical source parameters.
Towards a demonstrator for autonomous object detection on board Gaia
Shan Mignot
Show abstract
ESA's cornerstone mission Gaia aims at autonomously building a billion-star catalogue by detecting them on
board. The scientific and technical requirements make this an engineering challenge. We have devised a prototype
to assess achievable performances and assist in sizing the on-board electronics. It is based on a sequence
of four tasks: calibrating the CCD data, estimating the sky background, identifying the objects and, finally,
characterising them. Although inspired by previous similar studies (APM, Sextractor), this approach has been
thoroughly revisited and finely adapted to Gaia.
A mixed implementation is proposed which deals with the important data flow and the hard real-time
constraints in hardware (FPGA) and entrusts more complex or variable processing to software. This segmentation
also corresponds to subdividing the previous operations in pixel-based and object-based domains. Our hardware
and software demonstrators show that the scientific specifications can be met, as regards completeness, precision
and robustness while, technically speaking, our pipeline, optimised for area and power consumption, allows for
selecting target components. Gaia's prime contractor, inspired by these developments, has also elected a mixed
architecture, so that our R&D has proven relevant for the forthcoming generation of satellites.
Monitoring, diagnostic, and calibration of the Gaia astrometric instrument response within the astrometric verification unit
Show abstract
Micro-arcsecond precision must rely on the detailed knowledge of instrument parameters and observing conditions for
optimal definition of data reduction and calibration procedures. The variation of instrumental response over the field of
view with wavelength and in time is potentially critical and often unavoidable. This work addresses selected topics in
modeling of the astrometric instrument of the Gaia mission, evidencing their role in the data reduction strategy.
Discussion is extended to how the modeling will impact on the data quality and to how the science data can be used to
trace directly the instrument response. Finally mention is provided of the actual implementation of our recipe into the
Astrometric Instrument Model, a software tool which will be used during the processing of Gaia data.
Poster Session: Herschel
The data processing pipelines for the Herschel/SPIRE imaging Fourier transform spectrometer
Trevor R. Fulton,
Jean-Paul Baluteau,
George Bendo,
et al.
Show abstract
We present an update to the data processing pipelines that generate calibrated spectral data products from the Spectral
and Photometric Imaging Receiver (SPIRE), one of three scientific instruments onboard the European Space Agency's
Herschel Space Observatory launched on 14 May 2009. The pipelines process telemetry from SPIRE's imaging Fourier
Transform Spectrometer (FTS) taken in point source, jiggle- and raster-map observing modes, producing calibrated
spectra in low-, medium-, high-, and mixed low- and high-spectral resolution. While the order and algorithms of the data
processing modules in the spectrometer pipelines remain for the most part unchanged compared to their pre-launch
status, some improvements and optimizations have been realized through the analysis of data from the performance
verification and science demonstration phases of the mission. The data processing pipelines for the SPIRE FTS as of the
beginning of the routine phase of the Herschel mission are presented in their entirety, with more detailed descriptions
reserved for those elements that have changed since launch, in particular the first- and second-level correction steps for
glitches, the step that corrects for clipped samples, and the process by which Level-1 spectral data are converted to
Level-2 products. In addition, we discuss some of the challenging aspects still faced by the automated processing
pipelines, such as the removal of the contributions from the Herschel telescope and SPIRE instrument, and the relative
spectral response correction and flux conversion steps.
In-flight characterisation of Herschel-SPIRE optical performances
Show abstract
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space
Observatory, launched in May 2009 and now orbiting L2. This long wavelength instrument covers 200 to 670 microns
with a three band photometric camera and a two band imaging Fourier Transform Spectrometer.
We discuss the in-band SPIRE optical performances as obtained from measurements made during in-orbit
Commissioning and Performances Verification Phases. Complementary to the characterization of the instrument spectral
characteristics, attention is focused here on a set of dedicated observations made of unresolved bright sky targets mainly
obtained through the use of standard operating mode such as scan mapping. These tests were aimed at measuring the
geometry of the respective Photometer and Spectrometer field-of-views as well as the spatial response of the end-to-end
optical chain, from telescope to focal plane detectors in all spectral bands. Implications for instrument flight calibration
parameters are reported. Finally comparison with model-based results from design & build expectations and previously
reported ground-measured characteristics is given before concluding on the excellent state of the in-flight
Herschel/SPIRE optical performances; one of the key factors in the realization of the full scientific potential of the
Herschel observatory in the SPIRE spectral bands.
Status of the SPIRE photometer data processing pipelines during the early phases of the Herschel Mission
Show abstract
We describe the current state of the ground segment of Herschel-SPIRE photometer data processing, approximately
one year into the mission. The SPIRE photometer operates in two modes: scan mapping and chopped
point source photometry. For each mode, the basic analysis pipeline - which follows in reverse the effects from
the incidence of light on the telescope to the storage of samples from the detector electronics - is essentially
the same as described pre-launch. However, the calibration parameters and detailed numerical algorithms have
advanced due to the availability of commissioning and early science observations, resulting in reliable pipelines
which produce accurate and sensitive photometry and maps at 250, 350, and 500 μm with minimal residual
artifacts. We discuss some detailed aspects of the pipelines on the topics of: detection of cosmic ray glitches,
linearization of detector response, correction for focal plane temperature drift, subtraction of detector baselines
(offsets), absolute calibration, and basic map making. Several of these topics are still under study with the
promise of future enhancements to the pipelines.
Poster Session: Hubble
WFC3 detectors: on-orbit performance
Show abstract
Installed in the Hubble Space Telescope (HST) in May 2009, the Wide Field Camera 3 (WFC3) is performing extremely
well on-orbit. Designed to complement the other instruments on-board the Hubble Space Telescope (HST) and enhance
the overall science performance of the observatory, WFC3 is effectively two instruments in one. The UVIS channel,
with its pair of e2v 4Kx2K CCD chips provides coverage from 200 to 1000 nm while the IR channel, with a Teledyne
HgCdTe focal plane array (FPA) on a Hawaii-1R multiplexer, covers the 800-1700 nm range. This report summarizes
the performance of the WFC3 detectors, including primary characteristics such as quantum efficiency, read noise, dark
current levels, and cosmetics, as well as hysteresis prevention and the impact of radiation damage in the CCDs. In
addition, we discuss effects in the IR detector such as persistence, count rate non-linearity, 'snowballs', and 'negative'
cosmic rays.
Commissioning of the cosmic origins spectrograph on the Hubble Space Telescope: an overview of COS servicing mission observatory verification
Show abstract
The Cosmic Origins Spectrograph (COS) was installed into the Hubble Space Telescope (HST) during Servicing
Mission 4 (SM4) in May 2009. COS is designed to obtain spectra of faint objects at moderate spectral resolution (R >
16,000) in two channels: FUV, covering wavelengths from 1150 to 1450 Å; and NUV, covering 1700 - 3200 Å. Two
low resolution gratings (R > 1500) cover the < 900 - 2050 Å (FUV) and 1650 - 3200 Å (NUV) wavelength regions. An
imaging capability is also available on the NUV channel.
As part of the Hubble Servicing Mission Observatory Verification (SMOV) program, an extensive period of checkout,
fine-tuning and preliminary characterization began after the installation of COS. The COS SMOV program was a
cooperative effort between the Space Telescope Science Institute and the Instrument Definition Team based at the
University of Colorado. Nearly 2800 COS exposures in 34 separate observing programs were obtained during the course
of SMOV. Early activities included an initial instrument functional checkout, turn-on and initial characterization of the
detectors, NUV and FUV channel focus and alignment, and target acquisition verification and assessment. Once this
initial period was completed, science-related calibrations and verifications were performed in order to prepare the
instrument for normal science operations. These activities included wavelength calibration, flux calibration, detector flat
field characterization, spectroscopic performance verification, high S/N operation, and thermal and structural stability
measurements. We discuss the design, execution and results of the SMOV program, including the interrelationships
between the various tasks, and how the pre-launch plan was adjusted in real-time due to changing conditions.
HST/WFC3 in-orbit grism performance
Show abstract
The Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) is fitted with three grisms for slitless spectroscopy.
In the UVIS channel there is one grism, G280, for the near-UV to visible range (200 - 400nm;
1.4nm/pix). The IR channel has two grisms: G102 for the shorter (800-1150nm; 2.45nm/pix) and G141 for the
longer (1100-1700nm; 4.65nm/pix) NIR wavelengths. Using Servicing Mission Observatory Verification (SMOV)
and Cycle 17 calibration data we have assessed the performance of the grisms. We have measured the fielddependent
trace locations and dispersion solutions and determined the throughputs. The trace and wavelength
solutions for the IR grisms were found to be linear functions, varying smoothly across the field of view. The UVIS
grism exhibits a highly bent trace and significantly non-linear dispersion solutions. The maximum throughputs
for the G102 and G141 grisms, including the telescope optics, are 41% at 1100 nm and 48% at 1450 nm, respectively.
Limiting magnitudes at S/N=5 and a 1h exposure are JAB=22.6 and HAB=22.9 for the G102 and G141
grisms, respectively. The calibration results are published in the form of sensitivity and configuration files that
can be used with our dedicated extraction software aXe to reduce WFC3 slitless data.
Monitoring of the wavelength calibration lamps for the Hubble Space Telescope
Ilaria Pascucci,
Charles Proffitt,
Parviz Ghavamian,
et al.
Show abstract
The Space Telescope Imaging Spectrograph (STIS) and the Cosmic Origins Spectrograph (COS) are the two
optical-UV spectrographs on board the Hubble Space Telescope. To determine the wavelength scale for individual
science observations, internal arc lamp spectra accompany most observations of external targets. Here we present
a detailed analysis of the changes in the COS and STIS internal lamp fluxes and spectra over time, and also
compare our results to pre-launch ground testing, and to laboratory accelerated aging testing of similar lamps.
Most of the analysis presented here focuses on the behaviour of the lamps in the far-UV (FUV). We find that
the STIS LINE lamp has faded by a factor of ~15 in the very short FUV wavelengths (1150-1200Å) over the
13-year period on which STIS was in space, a much steeper fading than predicted from accelerated aging tests
in the laboratory. We also find that all STIS lamps have faded during the period in which the spectrograph was
not operational (2004-2009) thus pointing to on-orbit conditions as an additional and important cause of lamp
fading. We report that the COS P1 lamp output appears to decline with usage with a similar slope as the LINE
and HITM1 lamps on STIS. Finally, we recommend switching from the LINE to the HITM2 lamp for a more
efficient wavelength calibration of the STIS settings covering the very short FUV wavelengths.
Persistence and count-rate nonlinearity in the HST WFC3 IR detector
Show abstract
We now know that the flux of a source measured with HgCdTe arrays is not a simple, linear function, but depends on the
count-rate as well as the total number of counts. In addition to the count-rate non-linearity (and probably related to the
same physical mechanism), HgCdTe detectors are also susceptible to image persistence. Most of the persistence image
fades in a few minutes, but there is a longer-term component that can result in faint afterimages in the next orbit,
approximately 45 minutes later. For sources saturated at ~100 times full-well, the afterimages can persist for hours
afterwards. This report describes results from ground and on-orbit tests to characterize the persistence and the count-rate
non-linearity in the WFC3 IR detector during its first year of operation.
Poster Session: Instruments
Development and utilization of a point spread function for the Extrasolar Planet Observation and Characterization/Deep Impact Extended Investigation (EPOXI) Mission
Show abstract
The Extrasolar Planet Observation Characterization and the Deep Impact Extended Investigation missions (EPOXI) are
currently observing the transits of exoplanets, a comet nucleus at short range, and Earth using the High Resolution
Instrument (HRI) - a 0.3 m f/35 telescope - on the Deep Impact flyby spacecraft. The HRI is in a permanently
defocused state with the instrument point of focus about 0.6 cm before the focal plane due to the use of a reference flat
mirror that became a powered optic due to thermal warping during ground thermal-vacuum testing. Consequently, the
point spread function (PSF) covers approximately nine pixels FWHM and is characterized by a patch with three-fold
symmetry due to the three-point support structures of the primary and secondary mirrors. The PSF is also strongly color
dependent varying in shape and size with change in filtration and target color. While defocus is highly desirable for
exoplanet transit observations to limit sensitivity to intra-pixel variation, it is suboptimal for observations of spatially
resolved targets. Consequently, all images used in our analysis of such objects were deconvolved with an instrument
PSF. The instrument PSF is also being used to optimize transit analysis. We discuss development and usage of an
instrument PSF for these observations.
The ring of fire: an internal illumination system for detector sensitivity and filter bandpass characterization
Show abstract
We describe a prototype of an illumination system, the Ring of Fire (ROF), which is used as part of an internal
calibration system for large focal plane detector arrays in TMA (Three Mirror Anastigmat) telescope designs. Such
designs have been proposed for the SNAP (SuperNova Acceleration Probe) version of a Joint Dark Energy Mission
(JDEM). The ROF system illuminates the focal plane with a light beam the closely matches that of the telescope and is
used for creating high spatial frequency flat fields and monitoring filter bandpasses for experiments that demand a highly
accurate characterization of the detectors. We present measurements of a mockup of this prototype ROF design
including studies in variations in illumination across a large focal plane.
Monte Carlo simulations as a tool for radiation damage evaluation
Show abstract
One critical aspect in designing a space mission is the assessment of the level of radiation damage to the equipment that
one can expect during the course of the mission. The radiation environment in L2 orbit, however, has not been studied as
extensively as in the Low Earth Orbit case. Fluka is a Montecarlo software developed by CERN and INFN and
extensively used in high energy experimental physics and engineering, shielding, detector and telescope design, and
cosmic ray studies. In this paper, we make use of FLUKA to model the geometry of the structures surrounding the
detector, in order to analyze the mitigation strategy (i.e.: shielding of the detector assembly) in a well defined case (the
Euclid-NIS instrument, which is in its early design phase). By using a realistic cosmic ray spectrum and composition, we
analyze the resulting dose of ionizing and non-ionizing radiation on the Euclid-NIS detectors, and other effects.
Poster Session: JDEM
An attitude control testbed for JDEM
Show abstract
A mission critical goal of the JDEM mission is to resolve distant galaxies both optically and spectroscopically. In order to achieve this goal, the spacecraft must make observations at the diffraction limit. A full scale attitude control testbed was developed to determine the ability of preliminary designs to meet stringent attitude control requirements. We demonstrate our ability to control a realistic spacecraft structure to ~20 mas. Expected reaction wheel feedback effects are observed and mitigation discussed.
A simple optical design for a space Dark Energy Mission
Show abstract
Understanding the nature of the dark energy responsible of the apparent acceleration of the Universe is one of the most
challenging questions of our modern Cosmology and Fundamental Physics. On both side of the Atlantic a great deal of
effort has been spent to design and optimize space missions able to probe the nature of this dark energy. These missions
generally use two or three of the major cosmological probes: Baryonic Acoustic Oscillation (BAO), Weak Lensing
(WL) and Type Ia Supernovae (SNe). Many of the proposed missions concept rely on having different instruments
sharing a common optical interface and thus leading to a highly complex system. By adopting a different conceptual
approach we studied a fully integrated optical design yielding to a simple and more cost effective mission. The survey
strategy will also benefit from this design which offers a better time sharing between the different probes.
ACCESS: design and preliminary performance
Show abstract
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.
Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant
to many astrophysical problems. Systematic errors associated with problems such as dark energy now compete
with the statistical errors and thus limit our ability to answer fundamental questions in astrophysics.
The ACCESS design, calibration strategy, and an updated preliminary performance estimate are discussed.
Poster Session: JWST
The JWST/NIRCam coronagraph flight occulters
Show abstract
The NIRCam instrument on the James Webb Space Telescope will have a Lyot coronagraph for high contrast imaging of
extrasolar planets and circumstellar disks at λ=2 - 5 μm. Half-tone patterns are used to create graded-transmission image
plane masks. These are generated using electron beam lithography and reactive ion etching of a metal layer on an antireflection
coated sapphire substrate. We report here on the manufacture and evaluation of the flight occulters.
Simulation and image reconstruction of IFU-spectrometer data from JWST-MIRI
Show abstract
The Mid Infrared Instrument of the James Webb Space Telescope is equipped with an integral field unit (IFU)
spectrometer. The optical distortion in the image slicing and dispersive optics leads to non-uniform sampling
and a catenation of the spatial and spectral information on the detector plane. To enable the translation of
detector data to the three-dimensional data cube representing the two spatial and the spectral sky dimension,
we have built two software tools: The first is miri cube, an image reconstruction programme which translates
the detector data back into the sky cube. The second is an extended version of SpecSim, an IFU simulator which
simulates the image slicing and dispersion based on optical models of the instrument. With these tools we are
able to determine and implement the correct strategy for the end-to-end calibration of spectroscopy data during
the on-ground cryogenic test campaign.
Characterization of the tunable filter imager etalon on the JWST Fine Guidance Sensor
Show abstract
The Fine Guidance Sensor (FGS) on the James Webb Space Telescope (JWST) has a science observing capability
provided by the Tunable Filter Imager (TFI). The TFI incorporates dielectric coated Fabry-Perot etalon plates with a
small vacuum gap. The separation of the plates is controlled by the Etalon Control Electronics (ECE) board, using
piezoelectric actuators (PZTs) and capacitive displacement sensors (CDS). The TFI measures over the wavelength range
of 1.6 to 4.9 microns with a spectral resolution of R~100. We present the key components of the etalon system and the
approach for characterizing and testing the system. Initial results from assembly-level testing are also presented.
Compared sensitivities of VLT, JWST and ELT for direct exoplanet detection in nearby stellar moving groups
Show abstract
In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect
methods. Today, progress in the field of high contrast and angular resolution imaging has allowed direct images of
several exoplanetary systems to be taken (cf. HR 8799, Fomalhaut and β Pic).1-4 In the near future, several new
instruments are going to dramatically improve our sensitivity to exoplanet detection. Among these, SPHERE
(Spectro Polarimetric High contrast Exoplanet REsearch) at the VLT, MIRI (Mid Infra-Red Instrument) onboard
JWST and EPICS at the ELT will be equipped with coronagraphs to reveal faint objects in the vicinity of nearby
stars. We made use of the Lyon group (COND) evolutionary models of young (sub-)stellar objects and exoplanets
to compare the sensitivities of these different instruments using their estimated coronagraphic profiles. From this
comparison, we present a catalogue of targets which are particularly well suited for the different instruments.
Performance verification of the MIRI imager flight model at CEA
Show abstract
MIRIM is the imager of the Mid Infrared Instrument (MIRI), one of the three scientific instruments on the James Webb Space Telescope (JWST). MIRIM will provide imaging between 5.6μm and 25.5μm, low resolution spectroscopy (LRS) between 5 and 10μm, and coronagraphy at 10.65μm, 11.4μm, 15.5μm and 23μm.
The Optical bench Assembly of MIRIM Flight Model (FM) has been integrated and tested between 2008 and 2009 at CEA (Saclay, France). The tests consist in characterisation of optical performances at all wavelengths and in all three modes (imaging, spectroscopy and coronagraphy), using a test bench (or Ground Support Equipment - GSE) that has been developed for this purpose. The GSE comprises a helium cooled cryostat for the instrument itself, a proto-IR focal plane module (with JPL sensor chip and CEA electronics and housing), a warm telescope simulator that delivers a JWST-like beam, and computers and software for running automatic test procedures. It is designed to allow a large set of performance verifications, such as high-resolution PSF measurements, characterisation of coronagraphs, response to monochromatic line or resolving power of the spectroscopic mode, some of them being unique along the test program of the instrument.
After a short description of the test equipment, this paper focuses on the tests results. A full assessment of performances is given. When applicable, performances are cross checked with requirements.
Imaging mode and coronagraphy had already been validated on optically representative models along the MIRIM development plan, especially with the Engineering and Test Model (ETM) of MIRIM, early 2008. The FM test campaign allowed us to confirm that the flight model behaves as expected in these two modes. We also tested for the first time, and validated, the low-resolution spectroscopy mode.
OGSE telescope WFE testing at 30K
Show abstract
The James Webb Space Telescope (JWST) Optical Telescope Element (OTE) gathers the light from astronomical
objects and provides it to four scientific instruments and the observatory guider. The Canadian contribution to JWST, the
Fine Guidance Sensor (FGS), includes both the FGS-Guider and one of the science instruments, the Tunable Filter
Imager (FGS-TFI); both are packaged together and are functionally independent. The FGS OGSE (Optical Ground
Support Equipment) is used to simulate the image from the OTE and verify the optical performance of the FGS Guider
and TFI during instrument level testing. The OGSE consists of 25 separate telescopes, each of which simulates a point
source at a different field location. The OGSE must maintain alignment and image quality at the cryogenic (30-40K)
operating temperature of the FGS. This paper presents WFE (wavefront error) testing for one of the telescopes over a
temperature range from ambient to cryogenic operating temperatures (30 K). This test made use of a Zygo
interferometer with the standard Zygo transmission sphere replaced by a custom-made transmission sphere located in the
cryo vacuum chamber. Meanwhile, image position displacements (focus) during cooling down with respect to ambient
are also obtained by tracking the position of the transmission sphere. The results show that the WFE degrades from 19
nm (RMS) at ambient to 42 nm (RMS) at 30 K, while the image displaces about 5.6 mm at 30 K with respect to ambient
temperature. The reason for the focus displacement is discussed.
Optical wavefront characterization using phase retrieval for the NIRSpec demonstration model for the James Webb Space Telescope
Show abstract
Phase retrieval results are presented for the James Webb Space Telescope (JWST) Near InfraRed Spectrograph
(NIRSpec) demonstration model (DM). NIRSpec is one of five science instruments (SIs) comprising the Integrated
Science Instrument Module (ISIM); the NIRSpec is being built for the European Space Agency by a consortium led
by EADS Astrium GmbH. During this initial DM test campaign, focal-sweep images were collected over the
science field of view (FOV) for determining best focus at both ambient and cryogenic (cryo) temperature
environments, and these images were then used as input to the Hybrid Diversity Algorithm (HDA) for phase
retrieval, using Variable Sampling Mapping (VSM). Wavefront estimates from phase retrieval, an error budget, and
diagnostics used to assess phase retrieval stability and convergence are discussed. The ambient phase retrieval
results were compared against wavefront measurements taken with a Shack-Hartmann wavefront sensor.
Wavelength calibration of the JWST-MIRI medium resolution spectrometer
Show abstract
We present the wavelength and spectral resolution characterisation of the Integral Field Unit (IFU) Medium
Resolution Spectrometer for the Mid-InfraRed Instrument (MIRI), to fly onboard the James Webb Space Telescope
in 2014. We use data collected using the Verification Model of the instrument and develop an empirical
method to calibrate properties such as wavelength range and resolving power in a portion of the spectrometer's
full spectral range (5-28 μm). We test our results against optical models to verify the system requirements and
combine them with a study of the fringing pattern in the instrument's detector to provide a more accurate calibration.
We show that MIRI's IFU spectrometer will be able to produce spectra with a resolving power above
R = 2800 in the wavelength range 6.46 - 7.70 μm, and that the unresolved spectral lines are well fitted by a
Gaussian profile.
Speckle differential imagery performance using a JWST tunable filter etalon prototype
Show abstract
One of the four science instruments aboard the James Webb Space Telescope (JWST) is the Tunable Filter
Imager (TFI) provided as part of the Canadian contribution of the JWST Fine Guidance Sensor. The TFI
features a low-order Fabry-Perot etalon which enables imaging spectroscopy at an average resolving power of
100. TFI also includes a coronagraph for high-contrast imaging applications such as exoplanet imaging. In
this paper we demonstrate experimentally a TFI prototype etalon's performance of speckle suppression through
multi-wavelength imaging, a technique widely used by existent and future ground-based high contrast imaging
instruments. The improvement in contrast ranges from a factor of ~10 at large working angles increasing to a
factor of ~60 in the inner regions with very high signal. This result is consistent with our theoretical model.
MIRI-JWST spectrometer main optics flight model realization and performance test results
Show abstract
MIRI ('Mid Infrared Instrument') is the combined imager and integral field spectrometer for the 5-29 micron wavelength
range under development for the JWST. The Flight Model development of the Spectrometer Main Optics (SMO)
consisted of small design changes to improve optical performance, structural (dynamic) behaviour and integration based
on the experience and verification results of the previous Qualification and Verification models. A full test program was
performed in order to keep test efforts at the higher MIRI level as small as possible. The flight model underwent full
optical as well as mechanical qualification testing. In December 2008 the SMO was shipped, after successful integration
and verification, for final integration within the MIRI instrument.
This paper will describe the Flight Model improvements (based on the Qualification and Verification Model test results),
the problems and issues encountered during integration and verification and the verification test results.
Use of a pathfinder optical telescope element for James Webb Space Telescope risk mitigation
Show abstract
A Pathfinder of the James Webb Space Telescope (JWST) Optical Telescope Element is being developed to check out
critical ground support equipment and to rehearse integration and testing procedures. This paper provides a summary of
the baseline Pathfinder configuration and architecture, objectives of this effort, limitations of Pathfinder, status of its
development, and future plans. Special attention is paid to risks that will be mitigated by Pathfinder.
Applying the tool: stray light cross-checks of the James Webb Space Telescope
Dennis L. Skelton
Show abstract
System modeling of space observatories too large for end-to-end ground testing includes assessing levels of unwanted
radiant energy on focal plane arrays, commonly called "stray light." The need for stray light analyses parallels the need
for large telescope collecting apertures; both seek to maximize sensitivity.
Mathematical modeling of stray light is unlike other engineering analyses, and the differences often lead to unfamiliarity
and subsequent underrating of its importance. Fortunately, the JWST Project undertook these analyses early enough to
guide important aspects of the optical and thermal control designs.
Software tools of unprecedented power continue in use to model the stray light performance of the James Webb Space
Telescope (JWST). This paper describes how one such tool is used by NASA's Goddard Space Flight Center (GSFC) to
provide cross-checks of analyses performed by JWST's industry partners. The methods described for JWST are broadly
applicable to other astronomical instrumentation.
Manufacturing and integration status of the JWST OSIM optical simulator
Show abstract
OSIM is a full field, cryogenic, optical simulator of the James Webb Space Telescope (JWST) Optical Telescope
Element (OTE). It provides simulated point source/star images for optical performance testing of the JWST Integrated
Science Instrument Module (ISIM). OSIM is currently being assembled at the Goddard Space Flight Center (GSFC).
In this paper, we describe the capabilities, design, manufacturing and integration status, and uses of the OSIM during the
optical test program of ISIM and the Science Instruments. Where applicable, the ISIM tests are also described.
Planetary system and star formation science with non-redundant masking on JWST
Show abstract
Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space
missions dedicated to either general astrophysics or extrasolar planetary astronomy. On the ground NRM
has opened a rich target space between 0.5 to 4 resolution elements from bright stars. It enabled moderate
contrast very high angular resolution observations that have provided dynamical masses for targets beyond the
resolution of the Hubble Space Telescope. Such observations challenge the best models of ultra-cool dwarf stars'
atmospheres and interiors. The technique succeeds because it sidesteps the effects of speckle noise that plagues
direct imaging at moderate Strehl ratios. On a space telescope NRM mitigates instrument-induced speckle
noise, thus enabling high contrast even when images are barely diffraction-limited. The non-redundant mask in
the Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) on the James Webb Space Telescope (JWST) will
open up a search space between 50 and 400 mas at wavelengths longer than 3.8μm. We present simulations that
estimate achievable contrast on JWST, and report preliminary results of a testbed experiment using a mask with
the same geometry as JWST's. We expect contrast of the order of 104 will be achievable in a 10 ks exposure
of an M = 7 star, with observing, target acquisition, and data calibration methods common to the three other
imaging instruments on board JWST. As an example of the potential science possible with NRM, we show that
if a planet were responsible for clearing the inner 5 AU of the disk around HR8799, it would likely be detectable
using JWST FGS-TFI's NRM at 4.6 microns. Stars as bright as M = 3 will also be observable with JWST's
NRM, meshing well with next-generation ground-based extreme adaptive optics coronagraphs. JWST NRM's
parameter space is inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes,
especially in the mid-IR.
Poster Session: Mirror Technology
Development and tests of interferometry facility in 6-m diameter radiometer thermal vacuum chamber in Tsukuba Space Center
Show abstract
We present a test of optical metrology for 800-mm spaceborne optics in the 6-m radiometer thermal vacuum chamber at
JAXA's Tsukuba Space Center of JAXA. Under the framework of the JAXA's large-optics study program for astronomy
and Earth observations, we developed a test bench for interferometric metrology of large optics with an auto-collimation
method in the chamber. The optical system was aligned in a horizontal light-axis configuration within the facility limit to
handle a 3.5-m aperture telescope like SPICA. A high-speed interferometer was contained in an aluminum and titanmade
pressure vessel, which was mounted on the five-axis stage. We tested the 800-mm lightweight C/SiC optics using a
900-mm diameter flat mirror. Alignment changes in tilts of about ten arcseconds were observed as pressure went down
from 1 atm to vacuum. After we re-aligned the interferometer and flat mirror, the wavefronts through the optics under
vacuum were observed to increase in astigmatism aberration by 0.07λRMS at λ=633nm from under atmosphere, which
might be caused by a deformation in the test optics or flat mirror.
ZERODUR 8m mirror for space telescope
Show abstract
In 2010 ESO will celebrate the 10th anniversary of the fourth 8 m telescope Yepun's first light event. Together with the
other VLT telescopes it has accumulated more than 40 years of extremely successful operation time for astronomy.
Progress in rocket technology and in ZERODUR® light weighting gives reason for contemplating about the use of the
last currently available 8.2 m blank for a space telescope. This paper will review the outstanding quality of the first four
mirror blanks and present the quality of the blank still available. Additionally we will give an overview over the progress
in the last decade in technology and knowledge and how they might support the use of the 8 m blank as space telescope
mirror.
Poster Session: nJASMINE
Nano-JASMINE: current status and data output
Show abstract
The current status of the Nano-JASMINE project is reported. Nano-JASMINE is a very small-sized (50 cm
cubic form) satellite that is expected to carry out astrometric observations of nearby bright stars. The satellite
will determine distances of more than 8000 stars by performing annual parallax measurements, which is the only
direct method to measure the distance of an astronomical object. The mission is required to continue for more
than two years to obtain reliable annual parallax measurements. In addition, Nano-JASMINE will serve as a
preliminary to the main JASMINE mission. We expect that Nano-JASMINE will be launched in August 2011
from the Alcantara Space Center in Brazil using the Cyclone-4 rocket.
CCD centroiding analysis for Nano-JASMINE observation data
Show abstract
Nano-JASMINE is a very small satellite mission for global space astrometry with milli-arcsecond accuracy, which
will be launched in 2011. In this mission, centroids of stars in CCD image frames are estimated with sub-pixel
accuracy. In order to realize such a high precision centroiding an algorithm utilizing a least square method is
employed. One of the advantages is that centroids can be calculated without explicit assumption of the point
spread functions of stars. CCD centroiding experiment has been performed to investigate whether this data
analysis is available, and centroids of artificial star images on a CCD are determined with a precision of less than
0.001 pixel. This result indicates parallaxes of stars within 300 pc from Sun can be observed in Nano-JASMINE.
Poster Session: Solar Planetary Science
The telescope and the double Fabry-Perot interferometer for the ADAHELI solar space mission
Show abstract
ADvanced Astronomy for HELIophysics (ADAHELI) is a Small Mission to study the structure and fast dynamics of
the low solar atmosphere, performing Visible-NIR monochromatic and broad-band observations. The mission will
achieve millimeter full disk observations as well. The ADAHELI Team has succesfully completed, in December
2008, the Phase A study awarded by the Italian Space Agency (ASI).
The Interferometer for SOlar Dynamics (ISODY), on board the ADAHELI satellite, comprises a Gregorian
telescope and its focal plane suite. The advanced design focal plane suite uses fast CMOS cameras for investigating
photospheric and chromospheric fast dynamics and structure. ISODY is equipped with a pioneering focal plane suite
composed of a spectral channel, based upon a tandem of Fabry-Perot interferometers operating in the visible-NIR
spectral region, a broad band channel for high resolution imaging, and a correlation tracker used as an image
stabilization system. ADAHELI's mission profile has been tailored to limit the spacecraft's radial velocity in the
Sunward direction, to not exceed ±4 km/s, during 95% of the yearly orbit, to allow a continuous use of the on-board
interferometer.
The thermo-optical design and experiment research on H[alpha] and white light telescope
Show abstract
In order to study the impact of the thermal environment on the optical performance of the Ha and White light
telescope(HWT), a thermo-optical experimental system is built test the optical performance of the HWT under a thermal
vacuum condition. This system is made up of four sub-systems: an optical system to be tested, a vacuum system, a
temperature measurement and control system, and a wavefront sensing system. The temperature conditions of the
thermo-optical testing are designed on the basis of the measurement and numerical simulation of the ground observing
condition. An integrated STOP test based on the HWT is performed. The optical performances of the HWT under
different vacuum degree and different thermal control conditions are tested using the wavefront sensing system. The
results show that when the temperature of the secondary mirror is below 40°C, the optical performance of HWT is about
λ/8, which satisfies the requirement of λ/6. The secondary mirror structure is the most effect to the system optical
performance, which is the key part improving HWT. After the analytical model of HWT is set up by using the finite
element analysis software MSC.PATRAN/NASTRAN, finite element based optical analysis (FEMOPT) software is
used to calculate the optical performance. The comparison of the temperature control condition simulation and
experimental results show that FEMOPT optical structural thermal integral analysis is reasonable.
Simulation of the metrology of the PROBA-3/ASPIICS formation flying solar coronagraph
Show abstract
Formation Flying is now considered to be the most promising and effective approach to deploy the forthcoming
generation of very large instruments in space. PROBA-3 is a technology mission devoted to the in-orbit demonstration of
formation flying techniques and technologies. PROBA-3 will implement a giant coronagraph (called ASPIICS) that will
both demonstrate and exploit the capabilities and performances of formation flying. ASPIICS is distributed on two
spacecrafts separated by 150m, one hosting the external occulting disk and the other the optical part of the coronagraph.
ASPIICS will incorporate metrology units which will allow determining both the absolute pointing and the relative
alignment of the formation. Photosensors located around the entrance pupil of the coronagraph will determine the
absolute positioning of the instrument by sensing the penumbra behind the occulting disk. Light sources located on the
rear-side of the occulting disk will allow verifying the alignment of the formation. We carried out a complete numerical
simulation of the metrology system and showed how corrections are derived from the measurements to be applied to
each spacecraft in case of misalignments. This simulation was validated by a scaled model of the coronagraph developed
at Laboratoire d'Astrophysique de Marseille. This study has been conducted in the framework of an ESA
"STARTIGER" Initiative, a novel approach aimed at demonstrating the feasibility of a new and promising technology on
a very short time scale (six months).
The space instrument SODISM and the ground instrument SODISM II
Show abstract
PICARD is a French space scientific mission. Its objectives are the study of the origin of the solar variability
and the study of the relations between the Sun and the Earth's climate. The launch is scheduled for 2010 on
a Sun Synchronous Orbit at 725 km altitude. The mission lifetime is two years, however that can be extended
to three years. The payload consists of two absolute radiometers measuring the TSI (Total Solar Irradiance)
and an imaging telescope to determine the solar diameter, the limb shape and asphericity. SOVAP (SOlar
VAriability PICARD) is an absolute radiometer provided by the RMIB (Royal Meteorological Institute of Belgium)
to measure the TSI. It also carries a bolometer used for increasing the TSI sampling and ageing control.
PREMOS (PREcision MOnitoring Sensor) radiometer is provided by the PMOD/WRC (Physikalisch Meteorologisches
Observatorium of Davos / World Radiation Center) to measure the TSI and the Spectral Solar Irradiance.
SODISM (SOlar Diameter Imager and Surface Mapper), is an 11-cm Ritchey-Chr´etien imaging telescope developed
at CNRS (Centre National de la Recherche Scientifique) by LATMOS (Laboratoire, ATmosphere, Milieux,
Observations Spatiales) ex Service d'A´eronomie, associated with a 2Kx2K CCD (Charge-Coupled Device), taking
solar images at five wavelengths. It carries a four-prism system to ensure a metrological control of the optics
magnification. SODISM allows us to measure the solar diameter and shape with an accuracy of a few milliarcseconds,
and to perform helioseismologic observations to probe the solar interior. In this article, we describe the
space instrument SODISM and its thermo-elastic properties. We also present the PICARD payload data center
and the ground instrument SODISM II which will observe together with the space instrument.
Stray light analysis and optimization of the ASPIICS/PROBA-3 formation flying solar coronagraph
Show abstract
PROBA-3 is a technology mission devoted to the in-orbit demonstration of formation flying techniques and technologies.
PROBA-3 will implement a giant coronagraph (called ASPIICS) that will both demonstrate and exploit the capabilities
and performances of formation flying. ASPIICS is distributed on two spacecrafts separated by 150m, one hosting the
external occulting disk and the other the optical part of the coronagraph. This part implements a three-mirror-anastigmat
(TMA) telescope. Its pupil is placed about 800mm in front of the primary mirror, a solution allowing an efficient baffling
and a high reduction of the stray light inside the instrument. A complete stray light analysis of the TMA has been carried
out to design the baffles and to establish the required roughness of the mirrors. The analysis has been performed in two
steps: first, by calculating the diffraction pattern behind the occulter due to an extended monochromatic source having
the diameter of the Sun; second, by propagating this diffraction pattern, through all the telescope optical components, to
the prime focal plane. The results obtained are described in this article.
Demonstrator of the formation flying solar coronagraph ASPIICS/PROBA-3
Show abstract
Formation Flying opens the possibility to conceive and deploy giant solar coronagraphs in space permanently
reproducing the optimum conditions of a total eclipse of the Sun ("artificial" eclipse) thus giving access to the inner
corona with unprecedented spatial resolution and contrast (low stray light). The first opportunity to implement such a
coronagraph "ASPIICS" will be offered by the European Space Agency (ESA) PROBA-3 technology mission devoted to
the in-orbit demonstration of formation flying technologies. Two spacecrafts separated by about 150 m form a giant
externally-occulted coronagraph: the optical part hosted by one spacecraft remains entirely protected from direct sunlight
by remaining in the shadow of an external occulter hosted by the other spacecraft. We developed and tested a scale-model
'breadboard' (i.e., 30m) of the PROBA-3/ASPIICS Formation Flying coronagraph. The investigations focused on
two metrology systems capable of measuring both the absolute pointing of the coronagraph (by sensing the projected
shadow and penumbra produced by the external occulting disk) and the alignment of the formation (by re-imaging light
sources located on the rear-side of the occulting disk with the optical part of the coronagraph). In this contribution, we
will describe the demonstrator and report on our results on the crucial question of the alignment and pointing in space of
long instruments (> 100 m) with an accuracy of a few arcsec. This study has been conducted in the framework of an ESA
"STARTIGER" Initiative, a novel approach aimed at demonstrating the feasibility of a new and promising technology on
a very short time scale (six months).
Calibration and alignment of the demonstrator of the PROBA-3/ASPIICS formation flying coronagraph
Show abstract
This article describes the calibration and alignment procedures of a demonstrator for the ASPIICS coronagraph proposed
for the ESA technology mission PROBA-3 aimed at demonstrating the feasibility of a Formation Flying coronagraph.
ASPIICS is distributed on two spacecrafts separated by 150 m, one hosting the external occulting disk and the other the
optical part of the coronagraph. The purpose of the demonstrator is to reproduce on ground the metrology systems that
will equip the coronagraph in order to realize the alignment of the two spacecrafts and the absolute pointing to the center
of the Sun. The demonstrator is composed of a device that reproduces the solar umbra/penumbra created by the solar
occulter[1] and of a Three Mirror Anastigmatic (TMA) telescope mounted on a hexapod, a new-generation platform that
allows 6 degrees of freedom. A large plane folding mirror is used on ground to obtain a distance between the occulter
and the TMA up to 30 m. Photo sensors located around the entrance pupil of the TMA determine the absolute positioning
of the instrument by sensing the penumbra behind the occulting disk. Light sources (LEDs) located on the rear-side of
the occulting disk allow verifying the alignment of the formation. The paper describes the whole demonstrator, its
integration, its calibration, and the performance of the metrology systems of the coronagraph. This study has been
conducted in the framework of an ESA "STARTIGER" Initiative, a novel approach aimed at demonstrating the
feasibility of a new and promising technology on a very short time scale (six months).
Analytic and experimental determination of ghosts in the Rosetta Narrow-Angle Camera and their impact on imaging performance
Show abstract
The Rosetta cometary rendezvous mission, one of ESA's cornerstone missions, was launched in 2004 and will be
inserted in orbit around comet 67P/Churyumov-Gerasimenko in 2014. One of its instruments, the Osiris Narrow Angle
Camera (NAC), will take high-resolution images of the comet and map its nucleus as well as the jets of gas and dust
emanating from localized areas. This is quite challenging as the contrast between the radiance of these jets and that of the
nucleus is expected to be of the order of 1/1000. A major limitation comes from the presence of multiple ghosts which
results from the presence of two filters and a protective window in front of the CCD detector. Rigorous knowledge of
these instrumental ghost images is therefore required. We present analytical models of the structure and intensity of these
ghosts, compare them with pre and post-launch observations, and describe image analysis tools developed to handle
them.
Poster Session: SPICA
Optical architecture of mid-infrared instruments (MIRACLE/MIRMES/MIRHES) 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 2018. Mid-infrared instruments for SPICA are
required to have three basic capabilities; a wide-field imaging, spectroscopic capability, and coronagraphic
capability as an option. First two capabilities are implemented by three instruments; MIRACLE(Mid-infRAred
Camera w/o Lens), MIRMES(Mid-IR Medium-resolution Echelle Spectrometer), and MIRHES(Mid-IR High-resolution
Echelle Spectrometer). Here, we present an optical architecture of the union of MIRACLE, MIRMES,
and MIRHES. MIRACLE has two channels (-S for short wavelength and -L for long wavelength) to cover the
wavelength range 5 to 40 micron. MIRACLE-L and MIRMES are packaged into one unit with common optical
bench and MIRACLE-S and MIRHES are packaged into another unit. Two units are independent with each
other and occupy different field of view of the SPICA telescope. Each unit has common fore-optics shared by
MIRACLE and MIR(M/H)ES. This fore-optics is designed using reflective mirror optics only, and has wide
filed of view(FOV). Most of the FOV is used by MIRACLE and small part of the FOV is used by MIRMES
or MIRHES. This structure of the instruments reduces the size and weight of the instruments. This benefit
outweigh the complexity of the instruments.
The digital processing unit of the SPICA SAFARI instrument: an FPGA based architecture using the Leon2-FT
Show abstract
The Digital Processing Unit (DPU) of the SAFARI instrument on board the SPICA satellite will be the bridge between
the Spacecraft Command and Data Management System and the other instrument subsystems. The DPU will implement
Telemetry and Telecommand exchange with the spacecraft, commanding and control of the subsystems, instrument
health monitoring, scientific data acquisition, compression and formatting. The DPU design has been driven by the
requirements for processing power, memory resources and data rates, as well as mass and power budgets. It will be based
on a LEON2-FT processor. All the data interfaces will be implemented using the SpaceWire standard protocols. In this
paper we provide the present status of the DPU design and describe a prototype board developed to study the
performance of the adopted solutions. The prototype board is based on an FPGA where the main DPU processor - a
LEON System on Chip - can be implemented. The breadboard provides the memory, connectivity and expandability
resources that make it a suitable platform for exploring and evaluating a wide range of HW/SW configurations, as
required during the early design phases of the SAFARI DPU. The main characteristics of the proposed processor and of
the performed tests are described as well.
Precision pointing control for SPICA: requirements and feasibility study
Show abstract
The SPICA mission aims to achieve high spatial resolution and unprecedented sensitivity in the mid to farinfrared
wavelength astronomy. We derived a set of pointing requirements from SPICA's mission requirements.
Disturbance management over the SPICA system and an implementation of isolators are necessary, because
cryogenic coolers' disturbances could generate vibration. Alignment and random pointing errors for focal-plane
instruments are reduced with a focal-plane guidance camera. Furthermore, an additional focal-plane camera and
a tip-tilt mirror actuator are installed for coronagraph mode. This paper presents an overview of the SPICA
pointing requirements and a feasibility study to achieve the requirements.
Polarization-interferometric eight-octant phase-mask coronagraph using ferroelectric liquid crystal for exoplanet detection
Show abstract
We report laboratory demonstrations of an eight-octant phase-mask (EOPM) coronagraph for direct detection of
exoplanets. The EOPM coronagraph is a family of a four-quadrant phase-mask (FQPM) one, and shows better
coronagraphic performance for partially resolved stars. We manufactured an eight-octant ferroelectric liquid-crystal
(FLC) mask. The FLC mask is composed of eight-segmented half-wave plates whose principal axes are different
between adjacent segments. The mask operates as a fully achromatic EOPM when the FLC mask is placed between
crossed polarizers. We carried out laboratory experiments on the EOPM coronagraph by using partially resolved whitelight
source, and compared the performance with that of the FQPM one. As a result, we confirmed that the EOPM shows
higher contrast than the FQPM. A drawback of the proposed method is that the FLC mask can be used only for one
component of polarization of incoming light because it is necessary to use the polarizer in front of the FLC mask. To
solve this problem, a two-channel coronagraph, based on two polarizing beam splitters instead of the polarizers, is
proposed. Observational efficiency can significantly be improved because the two-channel coronagraph enables us to
detect both components of polarizations from exoplanets. We also report preliminary experimental results of laboratory
demonstrations of the two-channel coronagraph.
Development of a wavefront correction system for the SPICA coronagraph instrument
Show abstract
We present the laboratory demonstration of a wavefront correction system for the SPICA project. We have been
developing SPICA Coronagraph Instrument (SCI) for exoplanet detection and characterization. SCI employs a wavefront
correction system with a 1024-element deformable mirror. The laboratory experiments demonstrated that 106 dynamic
ranges at 3.5 λ/D can be achieved after speckle nulling by using a DM at the He-Ne laser wavelength. We also started a
wide-band wavefront correction experiment in the visible wavelengths. The combination of wide-band speckle nulling
algorithm and a binary pupil mask will lead to a very wide-band, high contrast imaging system.
Conceptual design of a cryogenic system for the next-generation infrared space telescope SPICA
Show abstract
The conceptual design of the Space Infrared Telescope for Cosmology and Astrophysics (SPICA) has been studied as a
pre-project of the Japan Aerospace Exploration Agency (JAXA) in collaboration with ESA to be launched in 2018. The
SPICA is transferred into a halo orbit around the second Lagrangian point in the Sun-Earth system, where radiant
cooling is available effectively. The SPICA has a large IR telescope 3 m in diameter, which is cooled without cryogen to
below 6 K by the radiant and mechanical cooling system. Therefore, the SPICA mission will cover mid- and far-IR
astronomy with high sensitivity and spatial resolution during a long period of over 5 years for goal. Most heat radiation
from the sun and spacecraft is blocked by the Sun Shield and thermal radiation shields covered with Multi-Layer
Insulator (MLI) to limit heat radiation to the Scientific Instrument Assembly (SIA). The SIA, which is composed of the
primary mirrors and optical benches equipped with Focal Plane Instruments (FPIs), is refrigerated to below 6 K by two
sets of 4K-class Joule-Thomson (JT) cooler with a cooling power of 40 mW at 4.5 K. The Far-IR detector is refrigerated
to 1.7 K by two sets of 1K-class JT coolers with a cooling power of 10 mW at 1.7 K. Improvements for the higher
reliability and sufficient cooling performance are required in the development of SPICA mechanical cryocoolers.
Thermal analysis indicates that the SPICA cryogenic system works effectively to limit the total heat load on the SIA to
41.2 mW. This paper describes the conceptual design of the SPICA cryogenic system, which was established with
thermal feasibility for nominal operation mode.
Kinetic inductance detectors (KIDs) for the SAFARI instrument on SPICA
Show abstract
Kinetic Inductance Detectors (KIDs) with frequency domain read-out are intrinsically very suitable to use as
building blocks for very large arrays. KIDs therefore are an attractive detector option for the SAFARI instrument on
SPICA, Millimetron and also for large scale ground based imaging arrays. To study the properties of large KID
arrays we have fabricated 400 pixels array made from 40 nm thick Al films on high resistivity Si substrates. The
array is tested in a dry dilution refrigerator at 100 mK. We present the device design and experimental results. We
also present a new design of the array with lithographic air bridges over the coplanar waveguide feedline. The air
bridges are designed to suppress the slot line mode in the feedline and that will improve the pixel to pixel
reproducibility of large arrays.
Poster Session: Strategies
Overview of past and future space missions dedicated to exoplanet research
Show abstract
As more and more exoplanets are being discovered, there is a strong motivation for pushing the limits of current
detection methods and atmosphere characterization techniques. The scientific goal is ultimately to discover small rocky
exoplanets in the habitable zone of their host star and to determine whether their atmosphere contains any bio-markers.
Space observatories play an important role in this field, especially in the IR where ground telescopes are limited by
atmospheric absorption and where the star/exoplanet contrast is the lowest. This paper provides an overview of past and
current efforts in the field of space telescopes dedicated to exoplanet research, with an emphasis on ESA missions.
Spacecraft design drivers, highlighting the impact of exoplanet research requirements on the spacecraft design, are
explained when possible. A preliminary mission concept, assessed in the ESA Concurrent Design Facility (CDF),
dedicated to spectroscopic measurements of known exoplanets with the capability to observe several transits of a few
hundred exoplanets, is outlined and the key design challenges shortly discussed.
Poster Session: Systems Concepts
An alternative architecture for the PLATO Mission
Show abstract
PlaTO (Planetary Transits and Oscillations of stars) is one of the class M missions proposed to ESA for the Cosmic
Vision 2015-2025 program. It aims to find exoplanets by the transit method and to understand the hosting stars by
measuring their oscillations (asterosismology). The same wide field of view of about 1,800 deg2 will be observed during
3 years to achieve high precision photometry for a large number of stars (> 250,000). 42 telescopes, each one having
4 CCDs of 3584 x 3584 pixels will be read every 25 seconds generating a huge amount of data which cannot be
downloaded to Earth and represents a challenge for the classical software-based data processing solutions.
We present in this paper an alternative architecture based on FPGAs for the payload of the PlaTO satellite. The
capabilities of the FPGA allows to treat tens of megabits per second through a pipeline driven by the pixel arrivals so
that no buffering nor high speed clocks are required. This allows for treating multiple telescopes with a single FPGA and
drastically reduce the mass and power budgets. The software resources can then be used to perform complex processing.
Our alternative concept thus achieves precision at the theoretical limit together with major system-level improvements
on the satellite. It opens the opportunity to achieve the science requirements with a comfortable margin of about 20% or
to observe more stars.
The PLATO opto-mechanical unit prototyping and AIV phase
Show abstract
PLATO is the acronym of PLAnetary Transits and Oscillations of stars, and it is a mission proposed for the ESA Cosmic
Vision program in the Medium size program, with the target to detect and characterize exoplanets by the means of their
transit on a bright star. The instrumental overall layout proposed by the Plato Payload Consortium consists in a multitelescope
concept instrument, composed by several tens of telescope units, for which we are developing an all refractive
optical solution. These devices are characterized by a very large Field of View (more than 20 degrees on one side) with
an optical quality that fits most of the energy into a single CCD pixel. Such a goal can be achieved in a variety of
solutions, some including aspheric elements as well. A complete prototype of one telescope unit is foreseen to be built
initially (during phase B1) to show the alignment feasibility and, only in a second moment (Phase B2), to perform full
environmental and functional test. The aim of this article is to describe the alignment, integration and verification
strategy of the opto-mechanics of the prototype. Both the approaches of testing the telescope at the target working
temperature or to test it at ambient temperature around a displaced zero point, taking into account the effects of thermal
deformations, are considered and briefly sketched in this work.
Achieving milli-arcsecond residual astrometric error for the JMAPS Mission
Show abstract
The Joint Milliarcsecond Pathfinder Survey (JMAPS) is a small, space-based, all-sky, visible wavelength astrometric
and photometric survey mission for 0th through 14th I-band magnitude stars with a planned 2013
launch. The primary objective of the JMAPS mission is the generation of an astrometric star catalog with 1
milliarcsecond (mas) positional accuracy or better, and photometry to the 1% accuracy level or better at 1st
to 12th mag. Achieving this level of accuracy in the final catalog requires a demanding attention to reducing
systematic effects.
We present our findings on distortion, signal to noise, and the astrometric bandpass necessary to obtain the
desired accuracy for JMAPS.
Poster Session: TPF C
Practical numerical propagation of arbitrary wavefronts through PIAA optics
Show abstract
The phase-induced amplitude apodization (PIAA) coronagraph utilizes highly aspheric optics to produce a strongly
apodized beam without the large loss of light that would result from using a graded transmission mask. The rapid
variations in surface curvature at the edge of the PIAA apodizing optic creates large wavefront phase changes that
cannot be adequately represented in conventional Fourier-based diffraction propagation algorithms. A rapid technique is
required for propagating arbitrarily-aberrated wavefronts through the system. An alternative numerical method has been
proposed that combines a high-accuracy algorithm to compute edge diffraction effects with a quick modified angular
spectrum propagator that handles wavefront errors. We present the results of applying this method to realistically
aberrated wavefronts as compared to more complex and time consuming techniques.
A coronagraph system with unbalanced nulling interferometer: progress of wavefront correction
Show abstract
We have proposed a four-stage coronagraph system with an unbalanced nulling interferometer (UNI). It consists of a
first adaptive optics (AO), the UNI, a second AO, and a coronagraph. An important feature 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 aberration magnification of about 6 times and
compensated to about lambda/100 rms corresponding to lambda/600 rms virtually, and its performance is becoming
stable. We have put a 3-dimensional Sagnac interferometric nulling coronagraph at the final stage of the system and tried
to see the speckle reduction with the UNI-PAC system.
CIAXE: co-axial achromatic interferential coronagraph: first laboratory results
Show abstract
In 1996, Jean Gay and Yves Rabbia presented their Achromatic Interferential Coronagraph (AIC) for detecting
and imaging faint companions (ultimately exoplanets) in the neighboring of a star. As presented then,
the Michleson-like Interferometer configuration of the AIC hardens its insertion into an existing (coaxial) optical
train, the output beam of the AIC being delivered at right angle from the input beam. To overcome this, they
reconfigured the AIC into a compact and fully axial coronagraph, the CIAXE, which main feature consists of
using two thick lenses machined in the same optical material. For the CIAXE to deliver the output beam along
the same axis as the input beam, the two lenses are coaxially disposed on the optical axis and are separated, at
their common spherical contact surface by a thin air gap acting like a beam splitter. We have set up a laboratory
experiment aiming at validating the principle of the concept. Our first step was to equalize the thicknesses of the
two lenses, so as to make zero the optical path difference between both arms. For this, the (residual) value of the
OPD has been evaluated and then the lenses have been re-machined so as to decrease as far as technologically
possible, the thicknesses mismatch. As a second step, a micro-controlled rotation around the common curvature
center of the spherical surfaces of the lenses is applied. This allows a fine tuning of the residual OPD at the
required accuracy level. Are presented here test bench, steps and results.
Progress on broadband control and deformable mirror tolerances in a 2-DM system
Show abstract
Detection and Characterization of extrasolar terrestrial planets using coronagraphic techniques requires wavefront
control algorithms to relax tolerances in a space-based observatory. To minimize the time spent correcting
aberrations, the algorithms must function in broadband light. Two deformable mirrors in series can correct
for both amplitude and phase aberrations. By taking a linear approximation of the propagation between the
deformable mirrors we show an approach for broadband correction given a monochromatic estimate. We present
progress in monochromatic light, initial experiments for broadband wavefront correction. We also address the
additional challenges for a broadband controller such as limitations due to aberrations from spatial frequency
folding that exhibit a wavelength squared dependence, which requires a third deformable mirror to correct in
broadband. From these results we also discuss controllability of spatial frequencies and show its consequences
for both monochromatic and broadband correction when using two deformable mirrors in series.
Studies of the effects of actuator errors on the HCIT/PIAA contrast performance
Show abstract
The High Contrast Imaging Testbed Phase Induced Amplitude Apodization (HCIT/PIAA) coronagraph system at JPL
relies on an Electric-Field Conjugation (EFC) wavefront correction algorithm to create a high contrast point-spread
function (PSF). This algorithm works with one deformable mirror (DM) to estimate the electric-field to be controlled,
and with one or multiple DM's to create a "dark-hole" in the image plane. We have investigated the effects of DM
actuator errors on the efficiency of the EFC algorithm. The structural design of the optical system as well as the
parameters of various optical elements used in the analysis are drawn from those of the HCIT/PIAA system that have
been and will be implemented with one or two DM's. The simulation takes into account the surface errors of various
optical elements. In this paper, we report our findings in the case of narrowband wavelength light.
Low-cost high-precision PIAA optics for high contrast imaging with exo-planet coronagraphs
Show abstract
PIAA optics for high contrast imaging present challenges in manufacturing and testing due to their large surface
departures from aspheric profiles at the aperture edges. With smaller form factors and consequent smaller surface
deformations (<50 microns), fabrication of these mirrors with diamond turning followed by electron beam lithographic
techniques becomes feasible. Though such a design reduces the system throughput to ~ 50%, it still provides good
performance down to 2λ/D inner working angle. With new achromatic focal plane mask designs, the system performance
can be further improved. We report on the design, expected performance, fabrication challenges, and initial assessment
of such novel PIAA optics.
ACCESS pointing control system
Show abstract
ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) was one of four medium-class exoplanet
concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009 [14,
15]. The ACCESS study evaluated four major coronagraph concepts under a common space observatory. This paper
describes the high precision pointing control system (PCS) baselined for this observatory.
Annular groove phase mask coronagraph in diamond for mid-IR wavelengths: manufacturing assessment and performance analysis
Show abstract
Phase-mask coronagraphs are known to provide high contrast imaging capabilities while preserving a small inner
working angle, which allows searching for exoplanets or circumstellar disks with smaller telescopes or at longer
wavelengths. The AGPM (Annular Groove Phase Mask, Mawet et al. 20051) is an optical vectorial vortex coronagraph
(or vector vortex) induced by a rotationally symmetric subwavelength grating (i.e. with a period smaller than λ/n, λ being
the observed wavelength and n the refractive index of the grating substrate). In this paper, we present our first midinfrared
AGPM prototypes imprinted on a diamond substrate. We firstly give an extrapolation of the expected
coronagraph performances in the N-band (~10 μm), and prospects for down-scaling the technology to the most wanted L-band
(~3.5 μm). We then present the manufacturing and measurement results, using diamond-optimized microfabrication
techniques such as nano-imprint lithography (NIL) and reactive ion etching (RIE). Finally, the subwavelength grating
profile metrology combines surface metrology (scanning electron microscopy, atomic force microscopy, white light
interferometry) with diffractometry on an optical polarimetric bench and cross correlation with theoretical simulations
using rigorous coupled wave analysis (RCWA).
Simulations of coronagraphy with a dynamic hologram for the direct detection of exo-planets
Show abstract
In a previous paper,1 we discussed an original solution to improve the performances of coronagraphs by adding,
in the optical scheme, an adaptive hologram removing most of the residual speckle starlight.
In our simulations, the detection limit in the flux ratio between a host star and a very near planet (5λ/D)
improves over a factor 1000 (resp. 10000) when equipped with a hologram for cases of wavefront bumpiness
imperfections of λ/20 (resp. λ/100).
We derive, in this paper, the transmission accuracy required on the hologram pixels to achieve such goals. We
show that preliminary tests could be performed on the basis of existing technologies.
Poster Session: TPF Occulter
Design and implementation of the NUV/optical widefield Star Formation Camera for the Theia Observatory
Show abstract
The Star Formation Camera (SFC) is a wide-field (~19'×~15', >280 arcmin2), high-resolution (18 mas pixels) UV/optical
dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited
images at λ > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. The goal is to
conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births
and life cycles of stars and their planetary systems, and to investigate the range of environments, feedback mechanisms,
and other factors that most affect the outcome of star and planet formation.
Occulting ozone observatory ability to discover and locate single and multiple Earth-like planets in habitable zones
Show abstract
We present a study of the Occulting Ozone Observatory performance in observations of potential Earth-like
planets around nearby solar-like stars. We use Monte Carlo techniques to simulate planetary systems and
with assumptions about the signal-to-noise performance of the instrument we determine the significance of
planetary system parameter determinations--for example, can we conclude that a particular planet's semi-major
axis (SMA) is in the star's habitable zone? In addition to studying the dependence of the SMA
determination on the number of observations and detections, we present results on the ability to disentangle
and analyze the data from two-planet systems.
Error analysis on the NWO starshade
Show abstract
The New Worlds Observer enables high-contrast imaging by placing a space telescope in the dark shadow cast by an
apodized starshade. This starshade is fully opaque and its performance is determined by the precise shape of the petal-like
structure. In this paper, we describe our preliminary efforts to determine the tolerance of the starshade performance
to errors in this shape.
Progress at the starshade testbed at Northrop Grumman Aerospace Systems: comparisons with computer simulations
Show abstract
We report on progress at the Northrop Grumman Aerospace Systems (NGAS) starshade testbed. The starshade testbed is
a 42.8 meter vacuum chamber that replicates the Fresnel number of an equivalent full-scale starshade mission, namely
the flagship New Worlds Observer (NWO) configuration. This paper reports on recent upgrades to the testbed and
comparisons of previously published experimental results with computer simulations - which show encouraging
agreement to within a factor of 1.5. We also report on a new generation of sub-scale starshades that for the first time
allow us to exactly match the Fresnel number of a full-scale mission.
Dynamical performance for science-mode stationkeeping with an external occulter
Show abstract
An external occulter flown in precise formation with a telescope is being considered for high-contrast direct
imaging of exoplanets as a viable mission scenario. In this paper, the dynamics about the Sun-Earth L2 region for
an occulter-telescope constellation are considered in conjunction with fourth-body and solar radiation pressure
acting as disturbing forces. An optimal observation window is defined in terms of both thrust required and
the Sun-constellation geometry. By simulation, the effects of the stellar latitude and distance, the spacecraft
separation, the magnitude of the disturbing forces, and on-off versus continuous thrusting are quantified on the
thrusting profile needed to maintain precise alignment.
Starshade design for occulter based exoplanet missions
Mark W. Thomson,
P. Douglas Lisman,
Richard Helms,
et al.
Show abstract
We present a lightweight starshade design that delivers the requisite profile figure accuracy with a compact stowed
volume that permits launching both the occulter system (starshade and spacecraft) and a 1 to 2m-class telescope system
on a single existing launch vehicle. Optimal figure stability is achieved with a very stiff and mass-efficient deployable
structure design that has a novel configuration. The reference design is matched to a 1.1m telescope and consists of a
15m diameter inner disc and 24 flower-like petals with 7.5m length. The total tip-to-tip diameter of 30m provides an
inner working angle of 75 mas. The design is scalable to accommodate larger telescopes and several options have been
assessed. A proof of concept petal is now in production at JPL for deployment demonstrations and as a testbed for
developing additional elements of the design. Future plans include developing breadboard and prototype hardware of
increasing fidelity for use in demonstrating critical performance capabilities such as deployed optical edge profile figure
tolerances and stability thereof.
Poster Session: WFSC
First steps in the development of a piston sensor for large aperture space telescopes
Show abstract
Nowadays spaceborne missions for astronomy or Earth imaging need high resolution observation which implies the
development of large aperture telescopes. This can be achieved by multi-aperture telescopes or large segmented
telescopes. One of the major issues is the phasing of the sub-apertures or the segments of such telescopes. A cophasing
sensor is therefore mandatory to achieve the ultimate resolution of these telescopes.
In this framework, Liège Space Center (CSL) concern is the development of a compact cophasing sensor to phase new
large lightweight segmented mirrors for future space telescopes. The sensor concept has its origins in new phase retrieval
algorithms which have been recently developed.
In this paper, we outline the concept and the experimental validation results of our piston sensor breadboard which is
currently under development in our laboratory. Finally, future prospects and further developments of our experiment are
presented.
Advanced DFS: a dispersed fringe sensing algorithm insensitive to small calibration errors
Show abstract
Dispersed Fringe Sensing (DFS) is an elegant method of coarse phasing segmented mirrors. DFS performance
accuracy is dependent upon careful calibration of the system as well as other factors such as internal optical
alignment, system wavefront errors, and detector quality. Novel improvements to the algorithm have led to
substantial enhancements in DFS performance. In this paper, we present Advanced DFS, an advancement of
the DFS algorithm, which allows the overall method to be less sensitive to calibration errors. This is achieved
by correcting for calibration errors, which appear in the fitting equations as a signal phase term. This paper will
outline a brief analytical explanation of the improvements, results of advanced DFS processed simulations and
experimental advanced DFS results.
False diamond turning artifacts in phase retrieval results
Show abstract
Many modern optical designs employ diamond-turned optical components and utilize phase retrieval for metrology
during testing, assembly, and commissioning. The accuracy of the wavefronts obtained by phase retrieval depends on
the fidelity of the system model used during the retrieval, including knowledge of the pupil amplitude, and the
relationship between the digital sample spacing in the pupil and each point spread function (PSF), i.e., the plate scale.
However, recent simulations have shown that errors in the estimation of both the plate scale and unknown pupil
vignetting can both lead to mid-spatial-frequency groove-like errors in the wavefront maps obtained by phase retrieval.
In particular, these errors manifest themselves as concentric rings resembling diamond-turning tooling marks, and can
therefore easily confound metrology results involving diamond-turned components. Furthermore it was found that only
moderate amounts of pupil vignetting, and errors in sampling ratio as low as 2% produced groove errors consistent in
magnitude with typical diamond-turning specifications. This paper presents the results of this study on the magnitude
and nature of these artifacts and their impact on telescope metrology.