Following the new financial constraints imposed recently on ESA's programme in space science, a full re-evaluation of the long term plan was carried out in the first half of 2002 by ESA and its scientific advisory bodies. The exercise has resulted in a new plan called "Cosmic Vision" which not only preserves the missions previously approved but also includes two further low cost missions. The new plan, stretching over the present decade, is based on the implementation of new management tools briefly mentioned in this paper. In describing the new plan, emphasis is placed on space astronomy missions by providing a brief description of each mission's goals and characteristics. The paper also addresses technology activities in preparation of future projects foreseen for an implementation in the next decade.

In this paperm we introduce the activity of space infrared astronomy in Japan, the past mission: IRTS, ongoing mission: ASTRO-F and future mission: SPICA. Current status of the recent drastic change, reorganization of three space agencies in Japan is also reported.

SIRTF, -the Space Infrared Telescope Facility, is to be launched by NASA early in 2003. SIRTF will be an observatory for infrared astronomy from space with an 85cm aperture telescope operating at 5.5K and a 2.5-to-5 year cryogenic lifetime. SIRTF's three instruments with state of the art detector arrays will provide imaging, photometry, and spectroscopy over the 3-180um wavelength range. SIRTF will provide major advances for the study of astrophysical problems from the solar system to the edge of the Universe. SIRTF will complete NASA's family of Great Observatories and serve as a cornerstone of the Origins program. Over 75% of the observing time will be awarded to the general scientific community through the usual proposal and peer review cycle. SIRTF will demonstrate major advances in technology areas critical to future infrared missions. These include lightweight cryogenic optics, sensitive detector arrays, and a high performance thermal system, combining radiative and cryogenic cooling, which allows the telescope to be launched warm and to cool in space. These thermal advances are enabled by the use of an Earth-trailing solar orbit which carries SIRTF to a distance of ~0.6 AU from Earth in 5 years. This paper will provide an overview of the SIRTF mission, -telescope, cryostat, instruments, spacecraft, orbit, and operations - in preparation for an accompanying set of detailed technical presentations.

This paper describes the principal optical results of the "End to End" test conducted on the SIRTF Cryogenic Telescope Assembly. Test system focus was located using images from the shortest wavelength science instrument, IRAC, much as it will be on-orbit. Deep out-of-focus images were used to determine the system wavefront by Phase Retrieval methods with heritage to Hubble Space Telescope work. This work has been used to update the SIRTF optical models and aid in predicting the on-orbit performance of the observatory. Images made with other assemblies able to observe in the test (IRS, PCRS) were used to verify their function and co-focus to the IRAC established position. Image jitter was analyzed warm and cold, with visible images captured by the PCRS instrument and cold, with images captured by the IRAC instrument.

The Cryogenic Telescope Assembly (CTA) houses the SIRTF Science Instruments and provides them a 1.3 K temperature heat sink. It also provides the telescope, which is maintained at 5.5 K temperature in order to achieve the low photon background required for the 160 micron detector array. This unique cryogenic/thermal system provides the necessary cooling through passive means along with use of vapor cooling from the helium gas vented from the 360 liter superfluid helium cryostat. The cryostat vacuum shell temperature is low enough that the heat load to the helium reservoir is due almost entirely to instrument power dissipation, thus resulting in a predicted lifetime over 5 years. The corresponding helium loss rate is over 7 times lower than achieved by previously flown helium-cooled instrument systems, such as IRAS, COBE, and ISO. This extraordinary performance is made possible by the highly favorable thermal environment achieved in an Earth-trailing solar orbit at a distance of about 0.3 AU from the Earth. Attaining this outer orbit with the slight lift capacity of a Delta-II launch vehicle is made possible by the mass-saving approach of having the telescope outside the cryostat and warm at launch. The general end-to-end system architecture, verification approach, and predicted performance are discussed.

The Infrared Array Camera (IRAC) is one of three major scientific instruments to be launched aboard the Space Infrared Telescope Facility (SIRTF). This document briefly describes the features, usage, and limitations of the IRAC Science Data Simulator (ISDS) that can be used to generate simulated data to anticipate data quality and reduction issues for mission operations. The software is a combination of C++ and IRAF SPP routines that implement the features already characterized during the integration and test phase of IRAC's development. While no guarantee of accuracy is made, the intention is to replicate as faithfully as possible known characteristics and artifacts of the IRAC instrument. The many beneficial applications of the ISDS include facilitating planning of the IRAC pipeline by the SIRTF Science Center (SSC), and validating observing strategies for SIRTF Guaranteed Time Observers and Legacy teams. The simulator has already been used by mission planners to demonstrate the relative effectiveness of different approaches to data reduction. It will also be of great value in demonstrating IRAC's capabilities for mapping and source detection, and in testing post-pipeline software currently being developed for these purposes.

The NASA Space Infrared Telescope Facility (SIRTF) contains an 85 cm cryogenically cooled beryllium Ritchey-Chretien telescope. This Cryogenic Telescope Assembly (CTA) will operate at about 5 K. Once in orbit, the telescope may be focused by moving the secondary mirror using a cryogenic focus mechanism to vary the separation between the primary and secondary mirrors. The risk of failure of the motor is unknown but is believed to be non-negligible. It is therefore desirable to evaluate and achieve best focus with a minimum number of motor activations. The SIRTF Project has charged an Integrated Products Team (IPT) with conducting this activity. We describe a strategy to determine the initial mirror spacing by quantitatively evaluating the shapes of the images formed by the telescope using the Infrared Array Camera (IRAC) and other science instruments (SI's). We show that this information can be used to predict the direction and magnitude of the secondary mirror move that will result in the telescope best focus. The tools used to evaluate focus position and ptical quality of the in orbit CTA have been qualified during the ground-based BRUTUS test are here described. Future activities of the IPT to meet IOC objectives are summarized.

The SIRTF Cryogenic Telescope Assembly employs a multi-stage thermal/cryogenic system in which the telescope is cooled bo 5.5K by passive techniques combined with vapor cooling by the effluent from a superfluid helium cryostat. The cryostat and telescope are surrounded by an outer shell, which is passively cooled to an expected temperature of about 35K. Verifying the performance of this system by test cannot be practically accomplished by a single end-to-end test. In the SIRTF-CTA Performance Test, we verified the relationship between helium flow rate and telescope temperature with the outer shell held at its predicted flight temperature. For systems like the SIRTF-CTA with thermal time constraints of several days, schedule is a critical parameter when planning the test procedure. The original plan of two steady-state tests at two different flight-like thermal boundary conditions was supplemented when we discovered that the test-induced (background) heat load to the cryostat and telescope was an order of magnitude larger than the predicted flight levels. With these unforeseen heat loads, we amended the test plan to include multiple changes to the test boundary conditions to quantify the background heat sources. Because of schedule constraints, we did not h ave the luxury of establishing steady-state for the various conditions of interest, and we relied on analysis of the system transient response for verification. Here we present our investigation of test-induced heat loads, our approach to data analysis, a comparison of measured system performance to analytical predictions, and some lessons learned.

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Space Infrared Telescope Facility (SIRTF). IRAC is a four-channel camera that obtains simultaneous images at 3.6, 4.5, 5.8, and 8 microns. Two adjacent 5.12x5.12 arcmin fields of view in the SIRTF focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. We describe here the results of the instrument functional and calibration tests completed at Ball Aerospace during the integration with the cryogenic telescope assembly, and provide updated estimates of the in-flight sensitivity and performance of IRAC in SIRTF.

We describe the ground testing and characterization of the Multiband Imaging Photometer for SIRTF (MIPS). This instrument is a camera with three focal plane arrays covering broad spectral bands centered at 24 μm, 70 μm, and 160 μm. The instrument features a variety of operation modes that permit accurate photometry, diffraction-limited imaging, efficient mapping, and low resolution spectral energy distribution determinations. The observational philosophy of MIPS relies heavily on the frequent use of internal relative calibration sources as well as a high level of redundancy in the data collection. We show that by using this approach, users of MIPS can expect very sensitive, highly repeatable observations of astronomical sources. The ground characterization program for MIPS involved a number of facilities including test dewars for focal-plane level testing, a specialized cryostat for instrument-level testing, and tests in the flight SIRTF Cryo-Telescope Assembly

Two redundant AST-301 autonomous star trackers (AST) serve as the primary attitude sensors for JPL's space infrared telescope facility (SIRTF). These units, which employ a 1553B interface to output their attitude quaternions and uncertainty at a 2 Hz rate, provide a 1 σaccuracy of better than 0.18, 0.18, and 5.1 arcsec about their X, Y, and Z axes, respectively. This is a factor 5.5 better than the accuracy of the flight-proven AST-201 from which the trackers were derived. To obtain this improvement, the field of view (FOV) was reduced to 5 by 5 degrees, the accurate Tycho-1 and ACT catalogs were used for selecting the 71,830 guide stars, star image centroiding was improved to better than 1/50th of a pixel, and optimal attitude estimation was implemented. In addition, the apparent direction to each guide star in the FOV is compensated for proper motion, parallax, velocity aberration, and optical distortion. The AST-301 employs autonomous time-delayed integration (TDI) to achieve image motion compensation (IMC) about its X axis that prevents accuracy degradation, even at rates of 2.1 deg/s, making it actually suitable for use on spinning spacecraft. About the Y axis, a software function called "image motion accommodation" (IMA) processes smeared images to maximize the signal to noise ratio of the resulting synthetic images, which enables robust and accurate tracking at rates tested up to 0.42 deg/s. The AST-301 is capable of acquiring its attitude anywhere in the sky in less than 3 seconds with a 99.98% probability of success, without requiring any a priori attitude knowledge. Following a description of the 7.1 kg AST-301, its operation and IMA, the methodology for translating the night sky test data into performance numbers is presented, while, in addition, the results of tests used to measure alignment stability over temperature are included.

We present the performance results of the as-built Pointing Calibration and Reference Sensor (PCRS) for the Space Infrared Telescope Facility (SIRTF). A cryogenic optical (center wavelength 0.55 microns) imager, the PCRS serves as the Observatory's fine guidance sensor by providing an alignment reference between the telescope boresight and the external spacecraft attitude determination system. The PCRS makes precision measurements of the positions of known guide stars; these are used to calibrate measurements from SIRTF's star trackers and gyroscopes to obtain the actual pointing of the SIRTF telescope. The PCRS calibrates out thermomechanical drifts between the 300 K spacecraft bus and the 5.5 K telescope. We have demonstrated that the PCRS meets its centroiding accuracy requirement of 0.14 arcsec 1-σ radial. The PCRS was installed inside the SIRTF Cryo-Telescope Assembly in July, 2000 and has logged over 1000 hours of failure-free operation ever since. We have verified that the PCRS has survived all box-level environmental requirements, including the 1.4 K operating temperature, random vibration, pyroshock, and EMI/EMC, necessary to survive launch and operations over SIRTF's 2.5 year lifetime. Currently, the PCRS is undergoing testing as part of the recently integrated Observatory in preparation for a January, 2003 launch.

The Space Infrared Telescope Facility (SIRTF) will be launched in early 2003, and will perform an extended series of science observations at wavelengths ranging from 3.6 to 160 microns for five years or more. The California Institute of Technology has been selected as the home for the SIRTF Science Center (SSC). The SSC is completing the final stages of prelaunch development and testing of the Science Operations System (SOS), which will support science operations of the Observatory. The SOS supports a variety of functions including observing proposal submission by the scientific community, long range planning and short term scheduling of the Observatory, instrument performance monitoring during nominal operations, and production of a variety of scientific archival products. This paper describes the role and function of the SSC, the architecture of the SOS, and discusses the major SOS subsystems. Examples of products generated by the SOS are included

The Space Infrared Telescope Facility (SIRTF) observatory is an 85-cm telescope with three cryogenically cooled instruments. Following launch, the observatory will be initialized and commissioned for routine operations during a sixty-day period called In-Orbit Checkout (IOC), and a subsequent thirty-day period called Science Verification (SV). The emphasis for the IOC phase is to bring the observatory on-line safety and expeditiously, verify functionality of the instruments, telescope, and spacecraft, and demonstrate that the facility meets level-1 requirements. The emphasis of the SV phase is to characterize the observatory in-orbit performance, demonstrate capability for autonomous operations, conduct early release observations, and exercise the ground systems software, processes, and staffing sufficiently to commission the facility for routine operations. The design of the IOC/SV phases is dominated by two unique features of the SIRTF mission: the solar orbit that affects the thermal design and the communications strategy, and the warm launch architecture whereby the telescope is outside the cryostat and radiatively cools in deep space. The key challenges of SIRTF are in the areas of optical, cryogenic, and pointing control performance, which have dependencies on the performance of the three instruments, and vice versa. In addition, the mission and science operations teams must face the challenge of operating a new space observatory and safely establishing autonomous operations in a very short time. This paper describes a nominal mission plan that progressively establishes SIRTF capabilities during the IOC/SV phases, taking into consideration thermal, cryogenic, optical, communications, celestial mechanics, and operational designs and constraints.

The instruments of the Space Infrared Telescope Facility (SIRTF) are cooled directly by liquid helium, while the optical system is cooled by helium vapor. The greater the power dissipation into the liquid helium, the more vapor is produced, and the colder the telescope. Observations at shorter wavelengths do not require telescope temperatures as low as those required at shorter wavelengths. By taking advantage of this, it may be possible to extend the helium and mission lifetime by 10% or even 20%

ASTRO-F mission is the first Japanese satellite dedicated to infrared astronomy. The telescope has a 70cm diameter mirror, and is cooled down to 6 K with super-fluid helium assisted by a mechanial cooler system. The primary purpose of this project is to investigate the birth and evolution of galaxies in the early universe through deep, wide-field surveys at wavelengths ranging from 2 to 200 μm, as well as a wide field of observational studies in the infrared wavelength region. The spatial resolution and the point source sensitivity are nearly the same as those of the aperture diffraction limit and the natural background and/or confusion limit, respectively. In the far-infrared wavelength band, ASTRO-F will conduct an all-sky survey like the IRAS survey with several tens of times higher sensitivity and several times better spatial resolution. In the near- and mid-infrared, wide area sky-surveys will be conducted over pre-selected portions of the sky. In addition to these photometric surveys, low-resolution spectroscopic capabilities are available for all wavelength bands. The ASTRO-F mission will produce a fundamental database for the next generation of advanced observatories, for example, the Herschel mission, and NGST, and will complement the SIRTF mission by virtue of its wide sky coverage. The current development status of the ASTRO-F spacecraft, the observation plan, and the data reduction/analysis software are summarized. The launch by an M-V rocket is scheduled for February 2004.

The James Webb Space Telescope (JWST) - the 21st century follow-on to NASA's highly successful Hubble Space Telescope - has moved one step closer to becoming a reality. In addition to selecting the instrument and science teams, NASA announced on September 10, 2002 that TRW Space and Electronics and its partners - Ball Aerospace and Eastman Kodak - had won the prime contract to build the high-profile observatory, formerly known as the Next Generation Space Telescope. It will be up to the contractor team and NASA to finalize designs and being laying the groundwork for assemblying one of the largest single-aperture telescopes ever flown. This article provides a general overview of the JWST mission - a centerpiece of NASA's Origins Program - and describes some of the technological challenges that NASA and TRW face.

The infrared camera(IRC) onboard ASTRO-F is designed for wide-field imaging and spectroscopic observations at near- and mid-infrared wavelengths. The IRC consists of three channels; NIR, MIR-S and MIR-L, each of which covers wavelengths of 2-5, 5-12 and 12-26 micron, respectively. All channels adopt compact refractive optical designs. Large format array detectors (InSb 512x412 and Si:As IBC 256x256) are employed. Each channel has 10x10 arcmin wide FOV with diffraction-limited angular resolution of the 67cm telescope of ASTRO-F at wavelengths over 5 micron. A 6-position filter wheel is placed at the aperture stop in each channel, and has three band-pass filters, two grisms/prisms and a mask for dark current measurements. The 5 sigma sensitivity of one pointed observation is estimated to be 2, 11 and 62 micro-Jy at 4, 9, 20 micron bands, respectively. Because ASTRO-F is a low-earth orbiting satellite, the observing duration of each pointing is limited to 500 seconds. In addition to pointed observations, we plan to perform mid-infrared scanning observation. Fabrications of the flight-model of NIR, MIR-S, and the warm electronics have been mostly completed, while that of MIR-L is underway. The performance evaluation of the IRC in the first end-to-end test (including the satellite system) is presented.

Far-Infrared Surveyor (FIS) is one of the two focal plane instruments of ASTRO-F which is a Japanese infrared astronomical satellite and is planned to launch in 2004. The FIS has spectroscopic capability by a Fourier transform spectrometer (FTS) covering 50-200cm^-1 with spectral resolution of 0.2-0.33 cm^-1 in addition to the primary purpose of FIS (an all-sky photometric survey). The Martin-Puplett interferometer is adopted as the method for spectroscopy in order to achieve high optical efficiency in a wide wavelength range. The most important issue of the FTS is the development of driving mechanism in order to scan a moving mirror with high optical performances. By the present we succeed to develop the driving mechanism satisfying a lot of limitations and requirements as a instrument onboard satellite. Furthermore the wire-grid polarizers are evaluated in optical performance, these are usable for polarized interferomter. We also measure FIR spectrum using Spectroscopy mode of FIS, and many absorption lines of H₂O are detected on continuum spectrum of atmosphere. And the interferogram and spectrum are derived at low temperature (2K) that is practically used in space. The spectrum resembles expected one which are considered with optical components for flight model. The detection limit are estimated combining performances of optical components and detectors, the FISP has sufficient performance to archive objective sciences. FTS will provide a lot of astronomical information; determination of the SED in high-z objects detected by the survey observation of ASTRO-F, the redshift of such objects, and the physical conditions that are hard to be derived by optical/NIR-MIR observations, from FIR lines.

The Infrared Camera (IRC) is one of the focal-plane instruments on board ASTRO-F(Japanese Infrared Astronomical satellite to be launched in 2004). IRC will make imaging and spectroscopy observations in the near- and mid-infrared regions. IRC comprises of three channels; NIR, MIR-S and MIR-L, which cover 2-5, 5-12, and 12-26μm, respectively. In this paper we report the optical performance of the NIR imaging mode at cryogenic temperatures with three filters; N2, N3, and N4, which cover the wavelength regions of 2-2.7, 2.7-3.7, and 3.7-5.05μm, respectively. The NIR channel consists of three Si and one Ge lenses with the infrared array (412 x 512 format of InSb) manufactured by Raytheon IRO. At cryogenic temperatures (- 6K) we found slightly larger chromatic focal shifts than designed probably due to the uncertainty in low-temperature refractive indices of the lens materials. We obtained the modulation transfer function for each band by the knife-edge method and estimated the optical performance of the IRC with the telescope at cryogenic temperatures.

Future large aperture infrared space telescopes such as the Next Generation Space Telescope will require lightweight, deployable sunshields to enable passive radiative cooling to cryogenic operating temperatures. In addition to the requirement for a high performance thermal design, mechanical and structural requirements are also demanding due to constraints on mass and volume. NASA has supported several technology development efforts to reduce risks in the area of sunshield structures, including: system packaging and deployment, film management, materials characterization, modeling tools for thin-film membranes, and ground test capabilities for characterizing structural performance. This paper discusses recent progress in sunshield structures technology development relating to post-deployment structural performance. First, improved approaches for analyzing partially wrinkled, thin-film membrane structures will be discussed. Next, new techniques for static and dynamic testing of ultra-lightweight structures will be described. Finally, analytical and experimental results from two recent studies will be described: (a) dynamic characterization of a 1/10th scale sunshield model and (b) static shape characterization of a 1/20th scale sunshield membrane layer. Results from these studies will provide valuable resources for use in design of sunshields for future space telescopes.

The telescope onboard Japanese infrared astronomical satellite, ASTRO-F, forms an F/6 Ritchey-Chretien system with a primary mirror of 670 mm in diameter, the total weight of which is about 42 kg. The primary and secondary mirrors are made of a sandwich-type SiC material, consisting of light porous core and dense CVD coat of SiC. The whole system will be cooled down to 5.8 K with a combined use of super-fluid liquid helium and mechanical coolers on orbit. In order to estimate optical performance of the flight-model telescope at operating cryogenic temperatures, the primary mirror alone was first cooled and tested, and then the whole telescope assembly was tested at cryogenic temperatures. In both cases, the changes in the surface figure were measured from outside the cryostat by an interferometer for the temperature range of 10 K to 300 K. As a result, non-negligible degradation in wave-front errors of the primary mirror and the telescope assembly was detected at low temperatures. The deformation of the primary mirror was found to be mainly due to the thermal contraction of support structures and heat anchors, and degradation by the SiC mirror itself was much smaller. The observed wave-front error of the telescope assembly at 13 K, which was found to originate mainly from the distortion of the primary mirror, marginally meets the requirement to achieve the diffraction-limited performance at 5 microns. This paper summarizes the optical performances thus achieved at cryogenic temperatures for the ASTRO-F telescope.

A series of developmental as well as flight mirrors have been in process over the last few years for IR cryogenic telescope applications such as the Space Infrared Telescope Facility (SIRTF) and the Next Generation Space Telescope (NGST) and for visible ambient systems such as Space Based Laser (SBL). We will discuss the performance of the 0.85-m SIRTF primary mirror (26.6 kg/m² areal density) and the 0.5-m Subscale Beryllium Mirror Demonstrator (SBMD) beryllium mirror (9.8 kg/m² areal density) as well as the current status of the 1.4-m Ball semi-rigid, beryllium Advanced Mirror System Demonstrator (AMSD). The AMSD mirror itself has an areal density of 10.4 kg/m² and is currently in polishing. The entire AMSD assembly including composite reaction structure, flexures, and actuators, has an areal density less than 15 kb/m². Cyrogenic test results of the SIRTF and SBMD mirrors will be presented along with test data on the AMSD actuators. The SBMD mirror wsa cryofigured based on ambient and cryo testing to achieve a wavefront quality of 19 nm rms at 35 K. In addition, the effects of optically coating SBMD with a protected gold multi-layer system will be shown - demonstrating that a lightweight mirror can be coated without adverse print-through due to coating stress at ambient or cryo operating temperatures.

As part of its risk mitigation efforts related to large, future space-based deployable optics such as NGST, Lockheed Martin developed, implemented, and evolved a full-scale, lightweight, deployable petal structure and associated deployment mechanisms for cryogenic and microdynamic stability testing. The test-bed features a single petal assembly for an 8-meter diameter telescope, including a flight-like mirror support structure and full-size hinges and latches. The work completed on this test-bed include: 1) Characterization of the dynamics and microdynamics response of the full-scale petal and its hinge/latch interface to low-level vibration sources down to 0.1 nanometer, 2) Evaluation of petal deployment repeatability, 3) Evaluation of the performance of simple passive damping strategies for petal vibration control at cryogenic temperatures. In all respects, including microdynamics, deployment repeatability and stability, the hardware demonstrated performance well in excess of the NGST requirements. In this paper, we summarize the development and the results of the performance testing completed during the NGST Phase I formulation, including testing of hysteresis and deployment repeatability at room temperature.

An effort has been in place at Ball Aerospace & Technologies Corp. (BATC) for over three years to develop a mechanism for precise positioning of optical elements for such applications as the Next Generation Space Telescope (NGST). It is desired for such a mechanism to be of low mass, to have nanometer-level positioning capability over a comparatively large range of travel, to be both ambient and cryogenically capable, and to have high strength and stiffness capabilities. The development effort has resulted in a simple 288-gram mechanism that meets these requirements, and does so with a single stepper motor and a simple control system. Performance has been verified at both ambient and cryogenic temperatures, and the mechanism design is currently being implemented on BATC's Advanced Mirror System Demonstrator program (AMSD). The current design achieves steps of less than 10 nanometers per step over more than 20mm of travel. We will present an overview of the capabilities of the mechanism, as well as a discussion of the test results achieved to date. Test results will include both ambient and cryogenic performance, hysteresis and stiffness measurement, as well as verification of single-stepping capability.

The Lockheed Martin/Advanced Technology Center (LM/ATC) developed a lightweight, compact, high-load capable and yet high precision latch for use on deployable optical systems such as the Next Generation Space Telescope (NGST). The design allows precise self-centering and control of the stiffness at the latch interface. It also incorporates unique capabilities to evaluate the effects of gravity loads, latch preload level, creep, and very low vibration loads on the dynamics and microdynamics of the deployed instrument. The stiffness, nonlinearity and hysteresis characteristics of the latch and its catch flexure assembly were thoroughly tested in 6 axes down to the nanometer level at room temperature using the LM/ATC Compliance Measurement Device. The latch is stiff enough to hold an NGST-size mirror segment cantilevered against gravity allowing only small gravity sag when the primary mirror is horizontal, thus enabling end-to-end performance verification in 1-G in that orientation. The latch hysteresis is less than 1.0 nm/N under mechanical loads less than 25 N, which meets the NGST stability requirements with significant margin (20 nm at the tip of the petal in space environment). Several of these latches were integrated and demonstrated at the petal assembly level on a Single Petal Test-bed and the experimental results obtained on that test-bed are consistent with the component level results described in this report. We experimentally demonstrated that the latch engagement performance is not affected by exposure to cryogenic temperatures down to 20K, as required for use of the device on cryogenic infrared optical instruments such as NGST. A structural model of the latch was developed using Finite Element Analysis. Good correlation was obtained between the linear components of the analytical and of the experimental results: the model can therefore reliably be used in future NGST or other mission design efforts. This paper includes a brief description of the LM/ATC latch hardware and its principle of operation as well as the results of the modeling and the experimental characterization work performed on that hardware in the NGST Phase I formulation.

The successful augmentation of NASA's X-Ray Cryogenic Facility (XRCF) at the Marshall Space Flight Center (MSFC) to an optical metrology testing facility for the Sub-scale Beryllium Mirror Demonstrator (SBMD) and NGST Mirror Sub-scale Demonstrator (NMSD) programs required significant modifications and enhancements to achieve reliable data. In addition to building and integrating both a helium shroud and a rugged, stable platform to support a wavefront sensor, a custom sensor suite was assembled and integrated to meet the test requirements. The metrology suite consisted of a high-resolution Shack-Hartmann sensor, a point diffraction interferometer, a point spread function camera, and a radius of curvature measuring device. The evolution from the SBMD and NMSD tests to the Advanced Mirror System Demonstrator (AMSD) program is less dramatic in some ways, such as the reutilization of the existing helium shroud and sensor support structure. However, significant modifications were required to meet the AMSD program's more stringent test requirements and conditions resulting in a substantial overhaul of the sensor suite and test plan. This paper will discuss the instrumentation changes made for AMSD, including the interferometer selection and null optics. The error budget for the tests will be presented using modeling and experimental data. We will show how the facility is ready to meet the test requirements.

This paper describes the "End to End" optical test conducted on the Space InfraRed Telescope Facility (SIRTF) Cryogenic Telescope Assembly (CTA) in 2001. It was critical to verify SIRTF's optical functionality and quality under optical and thermal conditions that as much as possible simulated the flight environment. The Liquid Nitrogen cooled "Brutus" chamber at Ball Aerospace was the test facility. Flight-like self cooling, thermal blanketing, and auxiliary cooling loops allowed the assembly to reach temperatures close to orbital conditions. (25-5K) Introducing optical sources at the SIRTF focal plane allowed the telescope to perform as the collimating source. A motorized and cryogenically characterized reflection flat was used to direct the refocused images of test sources to visible and IR focal planes in SIRTF's Multi-Instrument Chamber. A sequence of tests was performed to gather data on system focus position, image stability, telescope wavefront and instrument assembly confocality.

The NGST Phase Retrieval Camera (PRC) is a portable wavefront sensor useful for optical testing in high-vibration environments. The PRC uses focus-diverse phase retrieval to measure the wavefront propagating from the optical component or system under test. Phase retrieval from focal plane images is less sensitive to jitter than standard pupil plane interferometric measurements; the PRC's performance is further enhanced by using a high-speed shutter to freeze out seeing and jitter along with a reference camera to maintain the correct boresight in defocused images. The PRC hardware was developed using components similar to those in NGST's Wavefront Control Testbed (WCT), while the PRC software was derived from WCT's extensive software infrastructure. Primary applications of the PRC are testing and experimenting with NGST technology demonstrator mirrors, along with exploring other wavefront sensing and control problems not easily studied using WCT. An overview of the hardware and testing results will be presented.

A piston sensing and control algorithm for segmented mirror coarse phasing using a dispersed fringe sensor (DFS) has been developed for the Next Generation Space Telescope (NGST) wavefront sensing and control. The DFS can detect residual piston errors as large as the order of a depth-of-focus and can phase the segment mirrors with accuracy better than 0.1 microns, which is well within the capture range of fine phasing for NGST. A series of experiments have been carried out on the NGST's Wavefront Control Testbed (WCT) to validate the modeling results, evaluate the DFS performance, and systematically explore the factors that affect the DFS performance. This paper reports the testbed results for several critical issues of DFS performance, including DFS dynamic range, accuracy, fringe visibility, and the effects of segment mirror aberrations.

We report on an algorithm enabling estimation of high dynamic range pupil phase without wrapping ambiguity. This algorithm was developed and validated using the NGST Wavefront Control Testbed (WCT-1), which permits introduction of aberrations and subsequent correction using 2 deformable mirrors. The algorithm is an extension of a Modified Gerchberg-Saxton iterative technique that incorporates both an evolving trial estimate as well as intermediate unwrapping. We will discuss results from WCT-1 that illustrate phase estimation when varying degrees of aberration are introduced.

To achieve and maintain excellent imaging performance, the Next Generation Space Telescope (NGST) will employ image-based phase retrieval methods to control its segmented primary mirror. In this paper, we present the experimental validation of a focus-diverse wave front sensing (WFS) algorithm with comparative interferometric measurements of a perturbed test mirror. Using sets of defocused point-spread functions measured with the NGST phase retrieval camera, we estimate the aberrations of the test optic in a perturbed and unperturbed state. Interleaved with the focus-diverse sets, we measure the surface figure of the mirror using a ZYGO interferometer. After briefly reviewing the basic WFS algorithm and describing the experimental setup, we show that we can obtain agreement that is better than 1/100th of a wave rms in the difference of the wave front estimates obtained in the perturbed and unperturbed states. Although this experiment does not establish the errors that are solely attributable to our WFS approach, it nevertheless validates the accuracy of our image-based methods for NGST, demonstrating that they are generally competitive with standard industrial optical metrology instruments.

The NGST Wavefront Control Testbed (WCT) is a joint technology program managed by the Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL) for the purpose of developing technologies relevant to the NGST optical system. The WCT provides a flexible testing environment that supports the development of wavefront sensing and control algorithms that may be used to align and control a segmented optical system. WCT is a modular system consisting of a Source Module (SM), Telescope Simulator Module (TSM) and an Aft-Optics (AO) bench. The SM incorporates multiple sources, neutral density filters and bandpass filters to provide a customized point source for the TSM. The telescope simulator module contains a flip-in mirror that selects between a small deformable mirror and three actively controlled spherical mirror segments. The TSM is capable of delivering a wide range of aberrated, unaberrated, continuous and segmented wavefronts to the AO optical bench for analysis. The AO bench consists of a series of reflective and transmissive optics that images the exit pupil of the TSM onto a 349 actuator deformable mirror that is used for wavefront correction. A Fast Steering Mirror (FSM) may be inserted into the system (AO bench) to investigate image stability and to compensate for systematic jitter when operated in a closed loop mode. We will describe the optical design and performance of the WCT hardware and discuss the impact of environmental factors on system performance.

The Segmented Telescope Control Software (STCS) uses science camera information to align and phase a deployable segmented optical telescope. It was developed the for the Next Generation Space Telescope (NGST) and has been successfully utilized on the Wavefront Control Testbed (WCT) for NGST and a portable phase retrieval camera (PPRC) system. The software provides an operating environment that will be used for the prime contractor's testbeds for NGST, and will eventually evolve into the Wavefront Sensing and Control (WFS&C) ground support software for NGST. This paper describes the engineering version of the STCS, the algorithms it incorporates, and methods of communicating with the testbed hardware.

The Wavefront Control Testbed (WCT) is used to demonstrate the wavefront sensing and control algorithms and procedures that will be used on the Next Generation Space Telescope (NGST). The Segmented Telescope Control Software, written in MATLAB®, is the primary development and operational tool used. The software has an extensive graphical user interface that allows the user to interact with the hardware and algorithms. A variety of additional software programs support the Segmented Telescope Control Software (STCS). Various hardware control software interacts with MATLAB via TCP/IP connections. When access to the hardware is unnecessary or undesirable, we can access the model server that simulates the system. A stand-alone safety monitoring LabVIEW program alerts technicians if a hardware failure occurs. A C program gives the operator a graphical way of monitoring the network connections to the various systems. An Interactive Data Language (IDL) data archiving routine creates a database to monitor and maintain the testbed data and executes the MATLAB to Flexible Image Transport System (FITS) translator. Additionally we have implemented a web-based bug tracking and plan to add experiment scheduling and a document archive. Due to the nature of the testbed, these software programs are constantly evolving, causing a variety of challenges over the years. This poster will describe these software elements and the issues that have arisen trying to use them together.

A method of coarse phasing segmented mirrors using white light interferometry (WLI) has been developed for the Next Generation Space Telescope (NGST) wavefront sensing and control. Using the broadband point PSF of the segmented mirrors taken during a segment piston scan, the WLI can accurately detect small residual piston errors. WLI does not rely on extra optics and uses only the final imaging camera. With its high sensitivity to small segment piston error WLI can be used as a complementary phasing algorithm to the dispersed fringe sensor (DFS) for NGST. This paper will present the results from modeling and experiment on the NGST's Wavefront Control Testbed (WCT).

The Next Generation Space Telescope (NGST) will be a segmented, deployable, infrared-optimized 6.5m space telescope. Its active primary segments will be aligned, co-phased, and then fine-tuned in order to deliver image quality sufficient for the telescope's intended scientific goals. Wavefront sensing used to drive this tuning will come from the analysis of focussed and defocussed images taken with its near-IR science camera, NIRCAM. There is a pressing need to verify that this will be possible with the near-IR detectors that are still under development for NGST. We create simulated NIRCAM images to test the maintenance phase of this plan. Our simulations incorporate Poisson and electronics read noise, and are designed to be able to include various detector and electronics non-linearities. We present our first such simulation, using known or predicted properties of HAWAII HgCdTe focal plane array detectors. Detector effects characterized by the Independent Detector Testing Laboratory will be included as they become available. Simulating InSb detectors can also be done within this framework in future. We generate Point-Spread Functions (PSF's) for a segmented aperture geometry with various wavefront aberrations, and convolve this with typical galaxy backgrounds and stellar foregrounds. We then simulate up-the-ramp (MULTIACCUM in HST parlance) exposures with cosmic ray hits. We pass these images through the HST NICMOS `CALNICA' calibration task to filter out cosmic ray hits. The final images are to be fed to wavefront sensing software, in order to find the ranges of exposure times, filter bandpass, defocus, and calibration star magnitude required to keep the NGST image within its specifications.

Experience and infrastructure from NGST's Wavefront Control Testbed (WCT) were utilized to develop a portable wavefront sensor, the Phase Retrieval Camera (PRC). The PRC is useful for the testing of optics in high-jitter environments. The principal uses of the PRC will be testing and experimenting with NGST technology demonstration mirrors as well as exploring other issues of wavefront sensing and control not easily studied using the WCT. This presentation will detail the packaging and hardware chosen for the PRC, the PRC software, and calibration of the instrument.

Marshall Space Flight Center (MSFC) has been performing optical wavefront testing at cryogenic temperatures since 1999 in the Space Optics Manufacturing Technology Center's (SOMTC's) X-ray / Cryogenic Facility (XRCF). Recently the cryogenic optical testing capability has been extended to a smaller chamber. This smaller horizontal cylindrical vacuum chamber has been outfitted with a helium-cooled liner that can be connected to the existing helium refrigeration system bringing the kilowatt of refrigeration capacity to bear on a 1 x 2 meter test envelope. Cryogenic cycles to 20 Kelvin, including set-up and chamber evacuation/backfill, are now possible in only a few days. Since activation and chamber characterization tests in September 2001, the new chamber has been used to perform a number of proprietary cryogenic tests on mirrors, adhesives, and actuators. A vibration survey has also been performed on the test chamber. Chamber specifications and performance data, vibration environment data, and optical test capability will be discussed.

A technique for measuring the low-order wavefront aberrations in segmented-mirror telescopes using in-focus point-spread functions -"PSF Monitoring" - has been developed for the Next Generation Space Telescope (NGST). PSF Monitoring will enable the continuous monitoring of the mirror segment alignment using the PSFs readily available in science data. An extension of PSF Monitoring - in-focus wavefront control, or the explicit determination and correction of wavefront errors from in-focus images - may allow for the nominal maintenance of the NGST mirror alignment without detracting from valuable science observing time. PSF Monitoring and in-focus wavefront control have been rigorously tested on the segmented aperture system of the NGST Wavefront Control Testbed (WCT). This paper presents the results of our experiments and simulations to characterize the capture range and accuracy on WCT, as well as a two-wavelength algorithm that has been used to extend the piston capture range. A real-time PSF Monitoring and control experiment on WCT will also be presented. Finally, we show preliminary simulation results of PSF Monitoring on the two candidate NGST systems.

Much recent attention has been paid to wavefront sensing by phase-diverse phase retrieval (PDPR): estimating the wavefront in an exit pupil based on point-spread function measurements that incorporate known additional aberrations. The Next-Generation Space Telescope (NGST), for example, is expected to rely on this technology. This paper studies narrowband PDPR via "point-by-point" reconstruction, which estimates the phase at each sampled point in the pupil plane without using basis functions. The performance of an iterative, point-by-point phase diversity (PD) algorithm is demonstrated on data from an NGST-oriented wavefront sensing and control testbed as well as simulated data. Encouraging performance is exhibited in simulation and on experimental images in the presence of mild, continuous aberrations; however, in the presence of larger, discontinuous aberrations the experimental performance is poorer. The estimation algorithm is also used to compute Cramer-Rao bounds (CRBs) for a simulated PDPR problem and to analyze their sensitivity to system parameters such as field-of-view, wavelength, and the amount of focus diversity.

Some proposed architectures for large telescopes in space such as the Next Generation Space Telescope (NGST) utilize a segmented primary mirror with active control. The image quality for those systems can be characterized by the quality of the point spread function (PSF). We will present results from our simulations that demonstrate the quality of the PSF at various wavelengths, as characterized by the metrics of Strehl Ratio and encircled energy fraction. These metrics capture the critical features of the PSF that ensure good spatial resolution of the core at the nominal diffraction limited wavelength without having excessive scattering into the nearby diffraction pattern for observations at shorter wavelengths. The relationship of the image quality to the spatial frequency content of the system wave front error and to the image motion that occurs during the exposure (line-of-sight jitter) are explored.

Because of concern over possible failure of the SIRTF cryogenic focus mechanism in space, the SIRTF Project Office has directed that the focus should be set before launch so that the telescope arrives in orbit as close to optimum focus as possible. Then focus evaluation and determination of any required focus change to achieve best focus must be carried out without the conventional approach of a focus slew. For these tasks we have created two methods: Simfit and Focus Diversity. Simfit is a procedure for comparing an observed stellar image with a family of simulated point-source images with a range of focus settings. With a sufficiently accurate as-built telescope model for creating the simulated images, the focus offset and direction can be accurately and unambiguously determined because of the change in image appearance with defocus. Focus diversity takes advantage of the variation of best-focus setting over the instrument's focal plane due to focal plane curvature and tilt and offsets between different instrument channels. By plotting an image quality parameter, such as noise-pixels, for observed stars at several positions on the focal plane versus a defocus variable, the focus error and direction can be determined. We have developed an efficient program for carrying out these procedures. The validity of this program has been successfully confirmed using point-source images observed with three bands of the IRAC camera during a double-pass optical test of SIRTF in a Ball Aerospace cryogenic test chamber. The two procedures are described and are illustrated with these results

Large segmented and distributed aperture telescopes increasingly rely on innovative imaging techniques such as phase diversity and phase retrieval. These algorithms obtain the phase aberration in a dynamic system by different estimation techniques using the information from in-focus and out-of-focus images of extended objects and point objects, respectively. These estimation techniques are generally iterative and suffer from the usual pitfalls of CPU demands and failure modes. An alternative method would be to obtain an expression for the wavefront directly from the phase diversity measurements. The optimal wavefront expression would be expressed as a polynomial times the unaberrated OTF derived from the aberrated PSF. In this paper, we first obtain the expansion of the aberrated PSF with an explicit dependence on the amount of diversity and explore the implications of varying amounts of diversity as well as different numbers of diversity planes. Finally, we discuss solutions for the wavefront expression.

Dispersed fringe sensor (DFS) using broadband point source can unambiguously estimate piston to several hundred microns. We demonstrate a rapid technique to analyze the data from a DFS. The technique is less susceptible to higher order aberrations and returns the average phase difference between two aperture elements.

The science program for the Next Generation Space Telescope (NGST) relies heavily on a high performance nearinfrared imager. A design which supports the observations outlined in the Design Reference Mission (DRM) and which also supports enhanced searches for "first light" objects and planets has been developed. Key features of the design include use of refractive optics to minimize the volume and mass required, tunable filters for spectroscopic imaging, and redundant imagers for fail-safe wavefront sensing.

We are proposing to implement an integral field unit in NIRSPEC the Near Infra-Red Spectrograph for the NGST. This unique IFU will cover a 2x2 arcsec^2 field of view sampled at 0.05" (or 3"x3" @0.07"). The spectral resolution will go up to 3000. We will present the optical design of this unit and its implementation inside the NIRSPEC instrument. We will also show the results from an analysis of the effects of diffraction and stray-light inside the module, as well as the original method of integration we are using.. This module will be built using the image slicer technology, including 40 slices, each 900μm thick. We are also developing an innovative mechanical structure for this unit including the magnifying optics and the slicer itself, providing a very compact unit. The implementation will have a small impact on the NIRSPEC instrument, with only one to three additional gratings to be implemented in the grating wheel. The limiting magnitude of this mode should reach AB=24-26 for a point source. This unit would provide, for a marginal cost, a unique opportunity to offer a very powerful 3D spectrograph on NGST. The NIRSPEC instrument is under the ESA responsibility, and this work is being conducted in the context of the Astrium-ESA phase A study to which we are participating.

The MIRI is the mid-IR (5-28μm) instrument for NGST and provides for imaging, cororographic, high- and low-resolution spectroscopic capabilities. Unlike to the other instruments on NGST, the MIRI must be cooled - to reduce the thermal background from the optics and because the detectors require an operating temperature of about 7k.. In this paper we summarise the science goals, the proposed overall opto-mechanical concept, the thermal design aspects, the detectors and the expected sensitivity of the instrument.

MIRI, the mid-IR instrument for NGST is being provided by a collaboration between a consortium of European institutes, ESA, NASA, JPL and US scientists, with the Europeans responsible for the optics module. The instrument will provide diffraction limited imaging and spectroscopic capability over the 5-28μm region with unprecedented sensitivity. In this paper we describe the current optical design of the medium resolution spectroscopy channel (MIRI-S). This uses a novel arrangement of dichroics, image slicers and spectrometers to optimise the division of a limited number of detector pixels between spatial and spectral information whilst working within the tight mass and volume constraints imposed by a space mission. We also present our design for reflective image slicers that are adapted properly for diffraction limited performance to provide a high throughput over the full wavelength range of the instrument.

The Next Generation Space Telescope (NGST) will include a suite of three observational instruments, including a Near Infrared multi-object Spectrograph (NIRSPEC). To achieve multi-object capability, the spectrograph must be equipped with a slit mask to position small apertures on a number of astronomical targets simultaneously. Unlike most ground based spectrographs, the NIRSPEC slit mask must be reconfigurable, so that it can be adapted and reused for each observation. Although a great deal of work has been put into the development of mirror and shutter arrays using MEMS technology, these devices are currently unproven and risky in space environments. Therefore, a Mechanically Actuated Reconfigurable Slit mask (MARS) is being developed by the NRC - Herzberg Institute of Astrophysics as an alternative in case MEMS devices do not achieve maturity in the required timeframe. The MARS device creates 50 slits in an opaque mask by translating individual metal shutters within an array of precise guide tracks. When two adjacent shutters are brought close together, a slit is formed between them. A unique, robust, and high-resolution actuation scheme has been developed to individually position the metal shutters with micron accuracy. It is based on a combination of custom electromagnetic and piezoelectric actuators working in a coordinated sequence of movements. This scheme incorporates the key goals of reliability, redundancy and low heat dissipation in the focal plane of the instrument. MARS has been modeled, and its principle components have been prototyped to test the feasibility of the concept. The model has undergone structural, thermal, electrical and magnetic analysis to ensure that it meets the restrictive requirements on mass, volume and launch survivability while maintaining very low power requirements and heat dissipation. The prototypes have shown that the MARS concept is a viable alternative for the NIRSPEC slit mask which is based on proven and stable technologies. Further development is underway to manufacture a prototype slit mask, and test its operation in a cryogenic (30 K) environment to simulate the actual conditions aboard NGST.

The Next Generation Space Telescope (NGST) will be equipped with a Multi-Object Spectrograph (MOS) in order to record simultaneously several hundred spectra in a single observation run. The selection of the objects in the field of view will be done by a MEMS-based device: a micro-shutter array (MSA). In Laboratoire d'Astrophysique de Marseille, we have developed since several years different tools for the modeling and the characterization of these MEMS-based slit masks. Our models, based on Fourier theory, address two key parameters for the MOS performance: contrast and spectral photometric variation (SPV). We present in this paper our calculation for SPV evaluation. The SPV requirement is < 10%, but as SPV is strongly dependent on the object position and wavelength, the required value cannot be reached. We propose two dithering strategies able to solve this problem: blind dithering and slit reconstruction. Also, we have developed a characterization bench to measure these parameters. Preliminary contrast measurement have been carried out on the micro-mirror array (MMA) fabricated by Texas Instrument, in order to simulate the actual MEMS device for NIRMOS. Contrasts of around 500 has been measured and effects of object position on the micro-mirrors have been revealed. Further measurements with additional parameters such as the size of the source, the wavelength, and the input and output pupil size are under way.

A wide field (6x6 arcmin²) Rapid Infrared-Visible Multi-Object Spectrometer (RIVMOS) has been designed and is being fabricated at NASA's GSFC as part of the Next Generation Space Telescope (NGST) development and new technology demonstration. The primary goal is to demonstrate that the microshutter arrays, currently being designed for the NGST Near Infrared Spectrometer (NIRSpec) as programmable 2D selection masks, can achieve the optical performance required for faint object imaging and spectroscopy. We developed an original optical design that includes both reflective and refractive optics. The primary goal of the design was to achieve high imaging quality in both imaging and spectroscopy modes over a very wide spectral range with all spherical surfaces. The required optical performance is achieved for both multi-object spectroscopy and camera imaging over the entire field-of-view. The optical design consists of six optical subsystems including (1) an image relay consisting of a three-mirror anastigmat (TMA), (2) the microshutter assembly, (3) a triplet collimating optic, (4) a grism/filter assembly, (5) a pupil imaging optic, and (6) a five element telecentric camera design. The all-spherical optical design reduces construction costs and facilitates fabrication of the optical assembly while maintaining an encircled energy of 2 pixels within the FOV for wavelengths between 0.6 and 5.0 microns. Three spectral resolution modes (R = 50, 2000, 4000) will be available for multi-object spectroscopy as well as cross-dispersed echelle spectroscopy at the highest spectral resolution. The low resolution mode will be provided by the direct view prism, whereas silicon grisms will be used for higher resolving power. This design provides an extremely wide spectral range, wide field, very compact, high resolution imager-spectrometer with multi-object capability.

Mechanisms operating in the cryovacuum are required to rotate filter and dichroic wheels, to tilt gratings and to flip in the beam of an internal calibration source. The design proposed here is based on similar mechanisms flown successfully on the liquid helium cooled European ISO-satellite and being presently under qualification for ESA's cooled HERSCHEL-satellite. Their main characteristics are high reliability during the 10 year lifetime in space, high precision and low heat dissipation in the cryovacuum.

Numerical simulations have been carried out to assess the opportunity to detect extrasolar planets with MIRI: the mid-IR instrument of NGST. Several coronagraphs and telescope designs have been investigated. As a result, we found that very young planets (50Myr) as well as old planets (5Gyr) can be imaged in the thermal-IR (5μm to 20μm) down to a few Jupiter masses if an appropriate high-contrast coronagraph is in used. Promising results of numerical simulations are presented.

MIRI is the mid infrared instrument planned for the NGST. Working in the 5-28 μm band, it includes 3 units: a spectrograph, an imager and a calibration facility. We describe here the optical design of the MIRI imager channel as it is at teh end of the phase A study. The MIRI imager provides 3 observing modes: an imaging mode with a field of view of 1.3 arcmin x 1.7 arcmin and a Pixel Field of View of 0.1 arcsec/pixel, a coronagraphic mode and a low resolution spectroscopic mode for point sources, between 5 μm and 10 μm, with a spectral resolution R = λ/Δλ around 100.

Instrumentation for the Next Generation Space Telescope (NGST) is currently in the Phase A definition stage. We have developed a concept for the NGST Fine Guidance Sensor or FGS. The FGS is a detector array based imager which resides in the NGST focal plane. We report here on tradeoff studies aimed at defining an overall configuration of the FGS which will meet the performance and interface requirements. A key performance requirement is a noise equivalent angle of 3 milli-arcseconds to be achieved with 95% probability for any pointing of the observatory in the celestial sphere. A key interface requirement is compatibility with the architecture of the Integrated Science Instrument Module (ISIM). The concept developed consists of two independent and redundant FGS modules, each with a 4' x 2' field of view covered by two 2048 x 2048 infrared detector arrays, providing 60 milli-arcsecond sampling. Performance modeling supporting the choice of this architecture and the trade space considered is presented. Each module has a set of readout electronics which perform star detection, pixel-by-pixel correction, and in fine guiding mode, centroid calculation. These readout electronics communicate with the ISIM Command & Data Handling Units where the FGS control software is based. Rationale for this choice of architecture is also presented.

The `Herschel Space Observatory' (or simply `Herschel' - formerly FIRST) is the fourth Cornerstone mission in the European Space Agency (ESA) science programme. It will perform imaging photometry and spectroscopy in the far infrared and submillimetre part of the spectrum, covering approximately the 57 - 670 μm range. The key science objectives emphasize current questions connected to the formation of galaxies and stars, however, having unique capabilities in several ways, Herschel will be a facility open for observing time proposals from the entire astronomical community. Because Herschel to some extent will be its own pathfinder, the issue of instrument calibration and data processing timescales has special importance. Herschel will carry a 3.5 metre diameter radiatively cooled passive monolithic telescope. The science payload complement - two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) - will be housed in a superfluid helium cryostat. Herschel will be placed in a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with the ESA cosmic background mapping mission Planck) in 2007. Once operational Herschel will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a competitive proposal procedure. This paper intends to provide a selfstanding overview of the Herschel mission, and to serve as an introduction to the more specialised Herschel papers that follow in this volume.

The Herschel/Planck ESA programme combines two ESA missions of the HORIZON 2000 programme, the cornerstone mission Herschel (formerly named Far InfraRed and Submillimetre Telescope - FIRST) and the third medium sized mission, Planck. Herschel is a multi-user observatory, observing in the far infrared and sub-millimetre part of the electromagnetic spectrum, in the wavelength range from 60 to 670 mm. The Planck mission is a survey mission dedicated to map the anisotropies of the temperature of the cosmic background radiation. Both missions are planned to be launched in February 2007 on a single Ariane V launcher from the European Space Port of Kourou in a dual launch configuration. Both missions use orbits around the 2nd Lagrangian libration point L2, that is approximately 1.5 million kilometres away from the earth in the anti-sun direction. The programme started the spacecraft development phase in April 2001 and will complete the design phase in Summer 2002. The paper gives an overview of the Herschel and Planck System Design and the project status

Since ten years ASTRIUM has developed sintered Silicon Carbide (SiC) technology for space applications. Its unique thermo-mechanical properties, associated with its polishing capability, make SiC an ideal material for building ultra-stable lightweight space based telescopes or mirrors. SiC is a cost effective alternative to Beryllium and the ultra-lighweighted ULE. In Complememt to the material manufacturing process, ASTRIUM has developed several assembly techniques (bolting, brazing, bonding) for manufacturing large and complex SiC assemblies. This technology is now perfectly mature and mastered. SiC is baselined for most of the telescopes that are developed by ASTRIUM. SiC has been identified as the most suitable material for manufacturing very large crygenic telescopes. In this paper we present the development of Φ 3.5 m telescope for Herschel Mission. Herschel main goal is to study how the first stars and galaxies were formed and evolved. The Herschel Space telescope, using silicon carbide technology will be the largest space imagery telescope ever launched. The Herschel telescope will weight 300 kg rather than the 1.5 tons required with standard technology. The Herschel telescope is to be delivered in 2005 for a launch planned for 2007.

The Beam Steering Mirror (BSM) subsystem is a critical part of the SPIRE Instrument for the ESA Herschel Space Observatory. It is used to steer the beam of the telescope on the photometer and spectrometer arrays in 2 orthogonal directions, for purposes of fully sampling the image, fine pointing and signal modulation. The UK Astronomy Technology Centre (ATC) is part of a consortium of 15 institutes in Europe and the USA which was formed to build SPIRE and which is lead by Dr M. Griffin of the University of Wales, Cardiff.

We describe the requirements and the main design features of the ground test and calibration facility for the Herschel SPIRE instrument. SPIRE has a large cold focal plane unit (approx 700 x 400 x 400 mm) with several internal temperature stages, and is designed to operate in orbit viewing a low emissivity 80-K telescope. The calibration facility is designed to allow all aspects of instrument behaviour, performance, calibration, and optimisation of observing modes to be investigated under flight representative conditions. The facility includes the following features: - A large test cryostat replicating the in-orbit thermal environment - An external telescope simulator and sub-millimetre sources allowing the instrument to be fed with a beam that accurately simulates the beam from the Herschel telescope. - Internal cold black body for absolute radiometric and flat field calibration - Cold neutral density filters and an internal shutter for control of the photon background conditions - A far infrared laser used for spectral calibration of the SPIRE spectrometer channel and to present a source with well understood beam modes to the instrument. - An external FTS to characterise the spectral response of the instrument in both the camera and spectrometer channel The ground test facility will be used to evaluate the flight model before delivery and will also be used to house and carry out tests on the flight spare focal plane unit both before launch and during mission operations.

SPIRE, the Spectral and Photometric Imaging Receiver, will be a bolometer instrument for ESA's Herschel satellite. The instrument comprises a three-band imaging photometer covering the 250-500 μm range, and an imaging Fourier Transform Spectrometer (FTS) covering 200-670 μm. This paper presents the requirements for and design of the photometer and spectrometer calibration/illumination sources, and the results of laboratory tests on prototypes. The photometer calibrator is an electrically heated thermal source of submillimetre radiation, the purpose of which is to provide a repeatable signal for in-flight monitoring of health and responsivity of the SPIRE photometer detectors. It is not required to provide absolute calibration or uniform illumination of the arrays, but it may be used as part of the overall calibration scheme. The spectrometer calibrator is located at a pupil at the second input port of the FTS. It is designed to enable matching of the telescope emission for a range of telescope temperature (60-90 K) and emissivity (2% - 10%). By matching the telescope emission at this port, the high background from the Herschel telescope emission can be nulled to a high degree, resulting in an interferogram in which the contribution from the astronomical source is not overwhelmed by the telescope offset. The flexibility for telescope matching inherent in the design is important, as the exact telescope parameters will be unknown until the satellite is in operation. The FTS calibrator will also be used to assist in the absolute calibration scheme for SPIRE FTS observations.

The Heterodyne Instrument for Far Infrared (HIFI) on ESA's Herschel Space Observatory is comprised of five SIS receiver channels covering 480-1250 GHz and two HEB receiver channels covering 1410-1910 GHz. Two fixed tuned local oscillator sub-bands are derived from a common synthesizer to provide the front-end frequency coverage for each channel. The local oscillator unti will be passively cooled while the focal plane unit is cooled by superfluid helium and cold helium vapors. HIFI employs W-band GaAs amplifiers, InP HEMT low noise IF amplifiers, fixed tuned broadband planar diode multipliers, and novel material systems in the SIS mixtures. The National Aeronautics and Space Administration's Jet Propulsion Laboratory is managing the development of the highest frequency (1119-1250 GHz) SIS mixers, the highest frequency (1650-1910 GHz) HEB mixers, local oscillators for the three highest frequency receivers as well as W-band power amplifiers, varactor diode devices for all high frequency multipliers and InP HEMT components for all the receiver channels intermediate frequency amplifiers. The NASA developed components represent a significant advancement in the available performance. The current state of the art for each of these devices is presented along with a programmatic view of the development effort.

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments for ESA's far infrared and submillimetre observatory, Herschel. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 x 25 pixels, each, and two filled Si bolometer arrays with 16 x 32 and 32 x 64 pixels, respectively, to perform imaging line spectroscopy and imaging photometry in the 60-210 μm wavelength band. In photometry mode, it will simultaneously image two bands, 60-85 or 85-130 μm and 130-210 μm, over a field of view of ~1.75' x 3.5', with full beam sampling in each band. In spectroscopy mode, it will image a field of ~ 50", resolved into 5 x 5 pixels, with an instantaneous spectral coverage of ~1500 km/s and a spectral resolution of ~ 175km/s. In both modes background-noise limited performance is expected, with sensitivities (5σ in 1h) of ~ 3 mJy or 3-10x10^-18W/m², respectively.

The Photoconductor Array Camera and Spectrometer (PACS) is developed by an European consortium led by MPE, Germany. It is one of 3 cryogenic focal plane instruments of the Herschel Space Observatory, 1 of the 4 cornerstone missions within the ESA Horizon 2000 programme. The instrument will cover the wavelength regime from 60-210μm to explore the cold universe. The input beam is distributed to 4 advanced IR-detectors - 2 Ge:Ga photoconductor arrays for spectroscopy and 2 bolometer detector arrays for photometry - via a complex and very compact optomechanical layout with approx. 50 passive and active optical mirrors and 4 precision mechanisms. The paper will give an overview about the final optomechanical and thermal design of the thermal mass dummy and the cryo qualification model of the PACS Focal Plane Unit (FPU). The manufacturing and coating techniques of the lightweight aluminum mirrors applied to fulfill the infrared performance requirements even under cryogenic conditions and the alignment plan and optical verification concept in the visible range is outlined. The advanced manufacturing and thermal treatment procedures for the all aluminum optical bench are described in detail. Special emphasis is given to the dedicated development and verification efforts of a sophisticated IR Black Paint with extremely high IR-absorption used for effective straylight suppression. The conceptual architecture of the 2 very temperature stable and homogenous calibration sources is reported.

SPIRE, the Spectral and Photometric Imaging Receiver, will be an imaging photometer and spectrometer for ESA's Herschel Space Observatory. The main scientific goals and design drivers for SPIRE are deep extragalactic and galactic imaging surveys and spectroscopy of star-forming regions in own and nearby galaxies. It comprises a three-band imaging photometer with bands centred at approximately 250, 360 and 520 μm, and an imaging Fourier Transform Spectrometer (FTS) covering 200-670 μm. The detectors are feedhorn-coupled NTD spider-web bolometers cooled to 300 mK by a recyclable ³He refrigerator with a cycle time of less than two hours and a hold time of more than 46 hours. The photometer field of view is 4 x 8 arcminutes (the largest that can be accommodated) and is observed simultaneously in the three spectral bands. The angular resolution is determined by the telescope diffraction limit, with FWHM beam widths of approximately 17, 24 and 35 arcseconds at 250, 360 and 520 μm, respectively. An internal beam steering mirror allows spatial modulation of the telescope beam, and mapping observations can also be made by drift-scanning the telescope. The FTS has a field of view of 2.6 arcminutes. It uses a dual-beam configuration with novel broad-band intensity beam dividers to provide high efficiency and separated output and input ports. The FTS scanning mirror has a linear travel of up to 3.5 cm, providing adjustable spectral resolution of 0.04-2 cm^-1 (λ/Δλ = 20 - 1000 at 250 μm). The instrument design, operating modes, and estimated sensitivity are described.

The design of the Fourier Transform Spectrometer for the Herschel sub-millimetre Spectral and Photometric Imaging Receiver (SPIRE) is described. This is an innovative design for a sub-millimetre spectrometer as it uses intensity beam splitters in a Mach-Zehnder configuration rather than the traditional polarising beam splitters. The instrument is required to have a resolution of 0.04 cm^-1; have a relatively large field of view (2.6 arcmin circular) and cover a large wavelength range - 200 to 670 microns. These performance requirements lay stringent requirements on all aspects of the design. The details of the optical; mechanical and electrical implementation of the instrument are discussed in the light of the science and engineering requirements and laboratory testing on development models of the mechanism and control system are reported.

The main scientific object of the Planck ESA (European Space Agency) mission is the imaging of the anisotropies of the Cosmic Microwave Background (CMB) over the whole sky, with unprecedented sensitivity and angular resolution. This target will be achieved by the synergic performance of the two instruments onboard: the High Frequency Instrument (HFI) and the Low Frequency Instrument (LFI). The first is composed of 48 bolometers observing in six spectral bands from 100 GHz to 857 GHz; the latter is an array of 46 radiometers covering four microwave bands from 30 to 100 GHz. A description of the Low Frequency Instrument, together with its characteristics and performance, is reported in this paper.

The High Frequency Instrument of the Planck satellite is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB). Its main goal is to map the CMB with a sensitivity of ΔT/T=2.10^-6 and an angular resolution of 5 arcmin in order to constrain cosmological parameters. Planck is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. The architecture of the satellite is driven by the thermal requirements resulting from the search for low photon noise. Especially, the passively cooled telescope should be at less than 50K, while a cascade of cryo-coolers will ensure the cooling of the HFI bolometers down to 0.1K. This last temperature will be produced by a gravity insensitive 3He/4He dilution cooler. This will be achieved at the L2 Lagrangian point of the Sun-Earth system. The whole sky will be observed two times in the 14 months mission with a scanning strategy based on a 1RPM rotation of the satellite. In addition to the cosmological parameters that can be derived from the CMB maps, Planck will deliver nine high sensitivity submillimeter maps of the whole sky that will constitute unique data available to the whole astronomical community.

The Planck-High Frequency Instrument (HFI) will use 48 bolometers cooled to 100mK by a dilution cooler to map the Cosmic Microwave Background (CMB) with a sensitivity of ΔT/T~2.10^-6 and an angular resolution of 5 minutes of arc. This instrument will therefore be about 1000 times more sensitive than the COBE-DMR experiment. This contribution will focus mainly on the thermal architecture of this instrument and its consequences on the fundamental and instrumental fluctuations of the photon flux produced on the detectors by the instrument itself. In a first step, we will demonstrate that the thermal and optical design of the HFI allow to reach the ultimate sensitivity set by photon noise of the CMB at millimeter wavelength. Nevertheless, to reach such high sensitivity, the thermal behavior of each cryogenic stages should also be controlled in order to damp thermal fluctuations that can be taken as astrophysical signal. The requirement in thermal fluctuation on each stage has been defined in the frequency domain to degrade the overall sensitivity by less than 5%. This leads to unprecedented stability specifications that should be achieved down to 16mHz. We will present the design of the HFI thermal architecture, based on active and passive damping, and show how its performances were improved thanks to thermal simulations.

Planck associated to Herschel is one of the next ESA scientific missions. Both satellites will be launched in 2007 on a single ARIANE V launcher to the 2nd Lagrange libration point L2. Planck is a Principal Investigator Survey mission and the Planck spacecraft will provide the environment for two full sky surveys in the frequency range from 30 to 857 GHz. Planck aims to image the temperature anisotropies of the Cosmic Microwave Background (CMB) over the whole sky with a sensitivity of ΔT/T = 2 .10^-6 and an angular resolution of 10 arc-minutes. This will be obtained thanks to a wide wavelength range telescope associated to a cryogenic Payload Module. The Planck mission leads to very stringent requirements (straylight, thermal stability) that can only be achieved by designing the spacecraft at system level, combining optical, radio frequency and thermal engineering. The PLANCK Payload Module (PPLM) is composed of a cryo-structure supporting and a 1.5 m aperture off-axis telescope equipped of two scientific instruments HFI (High Frequency Instrument) and LFI (Low Frequency Instrument). The LFI detectors are based on HETM amplifier technology and need to be cooled down to 20 K. The detectors for the HFI are bolometers operating at 0.1 K. These temperature levels are obtained using 3 different active coolers, a 20K sorption cooler stage, which need pre-cooling stages for normal operation (the coldest one is around 60 K). Finally, the telescope temperature must be lower than 60 K. To meet those requirements, a specific cryo-structure accommodating a multi-stages cryogenic passive radiator has been developed. The design of this high efficiency radiator is basically a black painted open honeycomb surface radiatively insulated from the warm spacecraft by a set of angled shields opened towards cold space, also called "V-grooves". The coldest stage offers a ~1.5 W net cooling capacity around 55 K. Specific design are implemented to guarantee the straylight performance. The impacts of these elements on the Planck straylight performance have been assessed. The Payload Module design, the thermal performances (temperature level and stability) and RF performances as well as the integration logic are presented in this paper.

At Penn State, two new instrument component technologies, namely silicon gratings and gaussian-shaped pupil masks, have been developed and are ready for producing high quality components for all three NGST IR instruments. Fabrication of silicon grisms with sizes up to 2 inches in dimension has become a routine process at Penn State thanks to newly developed techniques in chemical etching, lithography, and post-processing. The newly etched silicon grisms have a typical rms surface roughness of ~ 9 nm with the lowest of 0.9 nm, significantly lower than our previous ones (~ 20-30 nm) and have ~ 0.035 wave wavefront distortion at 0.6328 μm, indicating diffraction-limited performance in the entire infrared wavelengths (1.2 -10 μm) where silicon has excellent transmission. These processes have also significantly eliminated visible defects due to grating mask break during chemical etching. For the best grisms, we have less than 1 defect per cm². The measured total integrated scatter is less than 1% at 0.6238 mm, indicating similar or lower scatter in the IR when grisms are operated in transmission. Silicon grisms and silicon immersion gratings will both boost spectral resolving power by more than 3 times for NGST near-IR MOS and mid-IR camera and spectrograph without pushing current instrument design. The higher dispersed spectra can be selected either by a filter or a low resolution grism cross-disperser. Our current grating techniques allow us to make gratings with a groove period from a few microns to more than 100 microns. For the first order grism, the theoretical grating efficiency is beyond 80% with a single layer of AR coating. The immersion gratings will have similar grating efficiency. Based on our previous measurements of a silicon echelle grism, this kind of grism can provide ~ 60% efficiency when they are operated in high orders. We have also developed Gaussian-shaped pupil masks for high contrast imaging with the NGST IR cameras. Depending on its final mirror configuration, this kind of mask can offer 10^-6 contrast imaging as close as 5 lambda/D to a bright point source. The advantage of using this mask instead of a conventional graded Lyot coronagraph is that it is much easier to implement by simply inserting it at a pupil location to reach deep null. Therefore, the observing efficiency can be significantly improved. A prototype of this kind of mask has been tested at the Mt. Wilson 100inch telescope with adaptive optics and demonstrates 10^-3-10^-4 contrast at ~ 5 λ/D at the initial observations. The contrast level is comparable to an IR coronagraph in the same IR instrument, but is about one order of magnitude worse than the scattered light levels caused by the mirror surface. We have also studied other mask coronagraph designs for high contrast imaging. The hybrid and band-limited designs show great promise for further improving image contrast. The NGST IR cameras with new coronagraph designs will allow high contrast imaging for extra-solar planets and substellar companions around nearby stars.

Recent advances in new technology, optical pattern recognition encoders at NASA have resulted in high speed, reliable, compact position sensors for use in cryostatic space flight mechanisms. New encoder scale patterns and image processing algorithms combine with digital signal processors (DSP) and field programmable gate array (FPGA) logic elements to enable encoders with conversion rates in excess of 1.5 kHz (suitable for high speed servo motion control for mechanisms), linear resolutions of less than 10 nm, and angular resolutions in the single digit milli-arcseconds in relatively compact packages. Fiber optic light guides allow encoders to function in cryostats with extremely low power dissipation. Ambient test data for fiber optic configurations suitable for cryogenic environments are presented. Cryostatic test capabilities under development are discussed. Potential applications exist for NGST and other infrared and sub-millimeter missions, such as fine guidance sensing, attitude control, mirror segment position sensing, and mirror scanning.

Absorbing coatings for the HIFI and PACS spectrometers aboard the Herschel platform have been developed and optically characterized. Using radiation from an optically pumped far-infrared laser at wavelengths in the 90 - 900 μm range, the specular as well as the diffuse reflection - characterized by the Bi-directional Reflection Distribution Function - have been determined. The influence of polarization has been addressed too. Moreover, the absorption of non-absorbing diffusely reflecting surfaces, to be used for integrating spheres, has been determined using a low temperature calorimetric method.

Because they can vastly reduce the required collimated beamsize at a given diffraction-limited resolution, silicon immersion gratings and grisms are an enabling technology for high resolution infrared spectroscopy from space and are highly useful in a range of ground-based and airborne instruments. We have used anistropic etching techniques to produce diffraction gratings on bulky silicon substrates. These devices can serve as high resolution grisms (when used in transmission), as coarse front-surface gratings, or as very high resolution immersion gratings. We have been able to produce devices with high optical efficiency by insuring that their entrance faces and groove surfaces are optically flat and that the groove positions are correct to within tolerance appropriate to the wavelength where the gratings will be used. We report here on testing and evaluation of high resolution Si gratings both in transmission (grism) and in reflection (immersion) mode.

Grisms are an important tool for astronomical spectroscopy because they allow for very compact, straight-through spectrometer designs in systems that can double as imagers. In the infrared, silicon grisms offer the advantage of superior resolving power for a given beam size and opening angle, when compared to grisms made of low refractive index materials. Silicon grisms with symmetric profiles and a blaze angle of 54.7°, the natural result of anistropic etching of silicon substrates oriented with the (100) crystal plane exposed, are relatively easy to produce. Low-order grisms, however, must be blazed at much shallower angles and will therefore have highly asymmetric groove profiles. In order to achieve these shallow blaze angles, the silicon surface must be precisely oriented at a bias from the (100) plane before cutting and polishing the substrate. Production of gratings with blaze angles as small as 6° is more difficult than production of unbiased gratings because it is very sensitive to changes in the etching process parameters. In this paper, we discuss our techniques for etching highly biased surfaces in silicon wafers, along with the first results of our production and testing of highly biased silicon gratings, including SEM groove profile pictures and optical testing in reflection at 632 nm and in transmission at 1523 nm.

Deconvolution of infrared telescope images can partially recover the distribution of light in the sky. The light from point sources and extended sources is modeled as a grid of closely-spaced points. A matrix of influence coefficients contains the response of the telescope-instrument combination to light at the grid points. A non-negative least-squares routine finds the sky flux densities that reproduce the instrument data. A personal computer program and examples of infrared telescope data deconvolution are presented.

One of the main limitations to the sensitivity of photodetector operated in space comes from responsivity variations and glitches caused by the impacts of charged particles. An international glitch working group (GWG) was created in order to centralize information about these phenomena and prepare future space experiments. Results about the infrared camera ISOCAM on-board the Infrared Space Observatory (ISO) are presented here: - The presented glitch rate has been analytically evaluated and compared to in-flight measurements - The study of temporal and spatial properties of glitches has led to a classification into 3 distinct families. These families are related to the linear energy transfer (LET) of charged particles interacting with the detectors. - Removal of methods of glitch efforts are briefly addressed. - Monte Carlo simulations of radiatiaon effects have been made. Glitch rates, spatial and energetic properties of glitches have been computed. Monte-Carlo results are compared with measured values. - Perspectices and current studies for HERSCHEL are discussed.

Raytheon Infrared Operations is under contract to develop 2K x 2K InSb arrays for the NGST NIRcam instrument and 1K x 1K Si:As IBC arrays for the NGST MIRI instrument. This paper reviews the progress in the NIR, showing NGST bare mux readout noise at 30 K of 2.4 e- and InSb dark current as low as 0.02 e-/s. Detectors and readouts have been fabricated in the 2K x 2K format and, except for adding indium bumps to the readouts, are ready for hybridization. Module and FPA designs are complete, resulting in a design that has self-aligning, interchangeable modules and requires no additional cold electronics to perform the NGST mission. Analysis predicts an alignment accuracy in the focus direction of ± 12 μm and total power for a 4K x 4K focal plane of 5 mW.

Rockwell Scientific Company is developing a new type of HgCdTe 1K 1K detector, called WFC3-1R, with cutoff wavelength at 1.7 m and 150K operating temperature. The detector will be installed on the Wide Field Camera 3, the fourth generation panchromatic instrument for the Hubble Space Telescope (HST) to be installed during HST Servicing Mission 4, currently scheduled for 2004. The detector uses HgCdTe MBE grown on a CdZnTe substrate and a new type of multiplexer, the Hawaii-1R MUX. Six lots of detectors have been produced so far, and have demonstrated the capability to meet or exceed the project requirements. In particular, detectors show quantum efficiency as high as ~90% at =1.4-1.6 m and greater than 50% at >1.0 m, readout noise of 30 e- rms with double correlated sampling, and dark current <0.2 e/s/pix at 150K. We illustrate the behavior of the reference pixels, showing that they allow the compensation of drifts in the dc output level. A number of detectors show a peculiar instability related to the variations of diode polarization, still under investigation. We also report on the environmental testing needed to qualify the WFC3- 1R detectors as suitable for flight on the HST. We finally provide an update of the project status.

The astronomical community has benefited from the scientific advances in photo-detection over the last few decades, from optical CCDs to infrared array detectors, for both large ground-based telescopes and space-borne telescopes. NGST, the successor to the Hubble Space Telescope, will draw on the improvements in infrared array technologies to achieve its goals and mission. The University of Rochester, in collaboration with Raytheon and NASA Ames Research Center, is developing and testing near infrared InSb array detectors to meet the stringent requirements for NGST. The latest development involves a suitable multiplexer in a 2048 x 2048 format that will be bump-bonded to an InSb array. Twenty of these arrays will be required for NGST imaging and spectroscopy. We present results for pathfinder 1024 x 1024 arrays. This is a companion work to the paper in these SPIE proceedings by Ken Ando, Peter Love, Nancy Lum, Alan Hoffman, Roger Holcombe, John Durkee, Joseph Rosbeck, and Elizabeth Corrales (Raytheon Infrared Operations).

We describe the on-orbit performance of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) aboard the Hubble Space Telescope (HST) following the installation of the NICMOS Cooling System (NCS). NICMOS is operated at a higher temperature (~77 K) than in the previous observing 1997-1998 period (~62 K). Due to the higher operating temperature, the detector QE is higher, while the well depth is less. The spatial structure of the flat field response remained essentially unchanged. We will show the effects of operating at the higher temperature and present current NICMOS calibration images. In addition, we present an overview of on-orbit testing and report on the re-enabling of NICMOS.

The HAWAII-2RG is a major upgrade of our prior 2048 x 2048 CMOS readout for astronomy (HAWAII-2) to support the requirements of the Next Generation Space Telescope and enable breakthrough capability for ground-based astronomy. By migrating to 0.25μm CMOS, for the first time guide mode readout is simultaneously supported in combination with various programmable science modes on a frame-by-frame basis. Consequently, the readout simultaneously supports programmable guide mode window and full-field science using the rest of the 4.2 million pixels at read noise <5 e-. Also for the first time with any imaging sensor, low and high background astronomy is supported using from 1 to 32 low-noise outputs via low-speed and high-speed signal paths. The latter supports throughput rate of up 320 MHz for real time imaging at >60 Hz. As with the HAWAII-2, the readout can be mated to our infrared and visible detector arrays including low dark current MBE HgCdTe at cutoff wavelengths from 1.5μm to 14μm, 2.5μm PACE HgCdTe, and silicon p-i-n detectors with superior quantum efficiency to backside-illuminated CCDs.

The Blocked Impurity Band (BIB) detector was invented in the early 1980's and subsequently developed by our team. The original arsenic-doped silicon (Si:As) detectors addressed the need for low-noise, radiation-tolerant, mid-IR detectors for defense surveillance from space. We have since developed large-format BIB focal plane arrays to address high-background requirements of ground-based telescopes and missile interceptors, low-background requirements of the Space Infrared Telescope Facility (SIRTF), and very low background requirements of the mid-IR instruments for the Next Generation Space Telescope (NGST) and Terrestrial Planet Finder. Most of these applications employ Si:As BIB detectors, but antimony-doped silicon (Si:Sb) BIB detectors are used for some SIRTF bands. Other demonstrated types including phosphorus (Si:P) and gallium-doped (Si:Ga) BIB detectors may have application niches. We have proposed development of a BIB detector type utilizing both Si:As and Si:P layers to optimize dark current vs. wavelength performance. Wavelength response for silicon BIB detectors extend to a maximum of ~40 microns (Si:Sb), but we have also demonstrated germanium BIB detectors for wavelengths extending to several hundred microns. We are currently developing germanium BIB detector arrays for astrophysics applications, including space telescopes beyond NGST.

A mid-infrared(5-30 micron) instrument aboard a cryogenic space telescope can have an enormous impact in resolving key questions in astronomy and cosmology. A space platform's greatly reduced thermal backgrounds (compared to airborne or ground-based platforms), allow for more sensitive observations of dusty young galaxies at high redshifts, star formation of solar-type stars in the local universe, and formation and evolution of planetary disks and systems. The previous generation's largest, most sensitive infrared detectors at these wavelengths are 256 x 256 pixel Si:As impurity band conduction devices built by Raytheon Infrared Operations for the SIRTF/IRAC instrument. Raytheon has successfully enhanced these devices, increasing the pixel count by a factor of 16 while matching or exceeding SIRTF/IRAC device performance. NASA-Ames Research Center in collaboration with Raytheon has tested the first high performance large format (1024 x 1024) Si:As IBC arrays for low background applications, such as for the mid-IR instrument on NGST and future IR Explorer missions. These hybrid devices consist of radiation-hard SIRTF/IRAC-type Si:As IBC material mated to a readout multiplexer that has been specially processed for operation at low cryogenic temperatures (below 10 K), yielding high device sensitivity over a wavelength range of 5-28 microns. In this paper, we present laboratory test results from these benchmark devices. Continued development in this technology is essential for conducting large-area surveys of the local and early universe through observation and for complementing future missions such as NGST, TPF, and FIRST.

ASTRO-F is a Japanese infrared satellite, which is scheduled for launch in early 2004. Far-infrared instrument that will be onboard ASTRO-F, Far-Infrared Surveyor (FIS), will perform the four-color all sky survey in the 50-200 um wavelength range with the diffraction-limited spatial resolution for 67-cm diameter telescope. For short-wave photometric bands of 50-110 um, we have developed a monolithic Ge:Ga two-dimensional array detector with no light cavity. This top-illumination type array design is promising for making future large-format array. The monolithic Ge:Ga is directly attached onto cryogenic readout electronics, capacitive trans-impedance amplifier composed of silicon p-MOSFETs, designed specially for low-temperature use. Results of the detector measurements show that the device works properly and sensitive enough for astronomical applications. Complex behavior of the detector, such as non-linearity of the integration ramp, transient response, non-uniform responsivity in the array, and cross-talk response, which may cause systematic error in the photometry, have been found. But, these effects are ~10% of major part of the signal and correctable with accuracy of a few %.

Cooled detectors for IR, visible, UV and X-rays often require a preamplifier that can operate at deep cryogenic temperature, down to the liquid-helium range. Preamplifiers based on available silicon or gallium arsenide transistors have not been entirely satisfactory. With this in mind, we have been developing junction field-effect transistors (JFETs) based on germanium. Our objective has been to achieve stable dc characteristics and very low noise down to as low a cryogenic as possible. We have obtained good dc characteristics down to liquid-helium temperature and low noise down to ≈30 K with Ge JEFTs. Between approximately 30 and 80 K, low-frequency gate-referred noise voltage is ≈30-60 nV/rtHz at 1 Hz, decreasing to <2 nV/rtHz above ≈1 kHz for 40 μm by 1560 μm gate n-channel Ge JFETs with drain current of 330 μA and dissipating approximately 400 μW. For lower and higher drain current the "1/f" noise remains approximately the same, but the white noise increases or decreases as expected. We are continuing development with the goal of extending the same low noise characteristics down to 4K.

The SuperNova/Acceleration Probe (SNAP) will measure precisely the cosmological expansion history over both the acceleration and deceleration epochs and thereby constrain the nature of the dark energy that dominates our universe today. The SNAP focal plane contains equal areas of optical CCDs and NIR sensors and an integral field spectrograph. Having over 150 million pixels and a field-of-view of 0.34 square degrees, the SNAP NIR system will be the largest yet constructed. With sensitivity in the range 0.9-1.7 μm, it will detect Type Ia supernovae between z = 1 and 1.7 and will provide follow-up precision photometry for all supernovae. HgCdTe technology, with a cut-off tuned to 1.7 μm, will permit passive cooling at 140 K while maintaining noise below zodiacal levels. By dithering to remove the effects of intrapixel variations and by careful attention to other instrumental effects, we expect to control relative photometric accuracy below a few hundredths of a magnitude. Because SNAP continuously revisits the same fields we will be able to achieve outstanding statistical precision on the photometry of reference stars in these fields, allowing precise monitoring of our detectors. The capabilities of the NIR system for broadening the science reach of SNAP are discussed.

Future infrared space missions will undoubtedly employ passively cooled focal planes (T ~ 30K), as well as passively cooled telescopes. Most long-wave detector arrays (e.g. Si:As IBC) require cooling to temperatures of ~ 6-8K. We have been working with Rockwell to produce 10μm cutoff HgCdTe detector arrays that, at temperatures of ~ 30K, exhibit sufficiently low dark current and sufficiently high detective quantum efficiency to be interesting for astronomy. In pursuit of these goals, Rockwell Scientific Company has delivered twelve 256 x 256 arrays (several of them engineering arrays), with cutoff wavelengths at 30K between 7.4 and 11μm for characterization at Rochester. Seven of these arrays utilize advanced structure diodes with differing capacitances arranged in rows (banded arrays), and the materials properties of the HgCdTe also vary significantly from array to array. Of ultimate interest to astronomy is the fraction of pixels with dark current below the target value of ~ 100e^-/s with 10-60mV of actual reverse bias across the diodes at T ~ 30K. These arrays were developed for the purpose of selecting diode architecture: we use this fraction as one criterion for selection. We have determined from these experiments the optimal diode architecture for future array development. Measurement of the dark current as a function of reverse bias and temperature allows us to ascertain the extent to which trap-to-band tunneling dominates the dark current at this temperature. We present the results for one representative array, UR008.

We summarize the current detector performance of the NearInfrared and MultiObject Spectrometer (NICMOS) on board the Hubble Space Telescope. After a three-year hiatus following the exhaustion of its solid nitrogen coolant, NICMOS was revived with the installation of the NICMOS Cooling System during the HST Servicing Mission 3B in March 2002. In this paper, we briefly describe the timeline of the NICMOS cooldown, present the results from the cooldown monitoring program to characterize the NICMOS detectors at their current operating temperature, and summarize the scientific performance of the "new" NICMOS.

In the coming decade, work will commence in earnest on large cryogenic far-infrared telescopes and interferometers. All such observatories - for example, SAFIR, SPIRIT, and SPECS - require large format, two dimensional arrays of close-packed detectors capable of reaching the fundamental limits imposed by the very low photon backgrounds present in deep space. In the near term, bolometer array architectures which permit 1000 pixels - perhaps sufficient for the next generation of space-based instruments - can be arrayed efficiently. Demonstrating the necessary performance, with Noise Equivalent Powers (NEPs) of less than 10^-20 W/√Hz, will be a hurdle in the coming years. Superconducting bolometer arrays are a promising technology for providing both the performance and the array size necessary. We discuss the requirements for future detector arrays in the far-infrared and submillimeter, describe the parameters of superconducting bolometer arrays able to meet these requirements, and detail the present and near future technology of superconducting bolometer arrays. Of particular note is the coming development of large format planar arrays with absorber-coupled and antenna-coupled bolometers.

The Japanese infrared astronomical satellite, ASTRO-F, employs the Far-Infrared Surveyor (FIS) for all sky survey. The FIS has two detector arrays; one covers from 50 to 110 μm wavelength, the other covers from 110 to 200 μm. Each of them uses Ge:Ga operating at 2K. We have developed and evaluated the preamplifiers for these detector arrays. The preamplifiers are required to work at 2K with low noise and low power dissipation. In this paper, we report on the development and evaluation of these cryogenic preamplifiers.

The Next Generation Space Telescope (NGST) Project is developing a new generation of near-infrared (NIR; λ=0.6-5 μm) array detectors optimized for ultra-low space-based backgrounds. NASA has selected the Independent Detector Testing Laboratory (IDTL) at the Space Telescope Science Institute (STScI) and the Johns Hopkins University to assist in testing and characterizing NGST's near-infrared detectors. In the IDTL, we have begun to explore how reference pixels might be used to calibrate infrared array data. Here we report some early results from these studies. Results to date are very encouraging, particularly with regard to techniques using temporal or spatial averaging to compute low-noise reference levels before making row-by-row reference pixel corrections. We explored the effectiveness of four potential calibration strategies using a shorting resistor installed where the detector would normally mount and are currently validating the techniques presented here using candidate NGST detectors.

Infrared detectors have advanced to the point where current devices are capable of achieving noise figures that are comparable to the background noise of space. Characterization tests done on these detectors at the NASA Ames Research Center have helped select the best devices for space telescopes. A highly customized system that can do these specialized tests has been developed with commercial off the shelf hardware. The data acquisition component of this system uses a pipelined architecture of multiple processors to enhance its real-time performance. This system can be customized for almost any array architecture and as more real-time performance is needed, additional processors can be incorporated. This approach permits large arrays to be tested at their maximum clocking rate.

The Independent Detector Testing Laboratory (IDTL) has been established by the Space Telescope Science Institute (STScI) and the Johns Hopkins University (JHU), and it will assist the Next Generation Space Telescope (NGST) mission in choosing and operating the best near-infrared detectors. The NGST is the centerpiece of the NASA Office of Space Science theme, the Astronomical Search for Origins, and the highest priority astronomy project for the next decade, according to the National Academy of Science. NGST will need to have the sensitivity to see the first light in the Universe to determine how galaxies formed in the web of dark matter that existed when the Universe was in its infancy (z ~10-20). To achieve this goal, the NGST Project must pursue an aggressive technology program and advance infrared detectors to performance levels beyond what is now possible. As part of this program, NASA has selected the IDTL to verify comparative performance between prototype NGST detectors developed by Rockwell Scientific (HgCdTe) and Raytheon (InSb). The IDTL is charged with obtaining an independent assessment of the ability of these two competing technologies to achieve the demanding specifications of the NGST program within the 0.6-5 μm bandpass and in an ultra-low background (<0.01 e-/s/pixel) environment. We describe the NGST Detector Characterization Project that is being performed in the IDTL. In this project, we will measure first-order detector parameters, i.e. dark current, read noise, QE, intra-pixel sensitivity, linearity, as functions of temperature, well size, and operational mode.

Intra-Pixel Sensitivity (IPS) is defined as the spatially varying response of the pixel to incoming flux. IPS plays a crucial role when the Point-Spread Function (PSF) is critically, or under-, sampled. Variations in IPS lead to photometric and astrometric errors. The Next Generation Space Telescope (NGST) requires high quality photometry and astrometry, so an accurate estimation of the IPS function is necessary for a successful NGST mission. Photo-electrons generated in a pixel may be detected in the depletion region (detection of the flux) of the same pixel, or might diffuse and end up in the microstructure of the detector, the electric field distribution therein, wavelength of the incident radiation, and diffusion processes of the excess charge carriers generated determines the IPS function of a pixel that can vary from pixel to pixel. The total detected flux is proportional to the convolution of the PSF and the IPS function. If we approximate the profile of the PSF, then the problem of determining the IPS function reduces to deconvolving using the experimentally obtained Sensitivity variation profile and the calculated PSF. We aim to obtain a highly undersampled PSF, scan it over a single pixel on a grid of 10 x 10 points, and retrieving IPS function using deconvolution. We present our results, experiment design, and the scope of further work, using an NGST detector, to estimate the IPS function at various wavelengths.

We report on the extensive tests to characterize the performance of the infrared detector arrays for the Infrared Camera (IRC) on board the next Japanese infrared astronomical satellite, ASTRO-F. The ASTRO-Fwill be launched early 2004 and the IRC is one of the focal plane instruments to make observations in 2-26μm. For the near-infrared observations of 2-5μm, a 512x412 InSb array will be employed, while two 256x256 Si:As arrays will be used for the observations of 5-26μum in the IRC. Both arrays are manufactured by Raytheon. To maximize the advantage of the cooled telescope and extremely low background radiation conditions in space, the dark current and readout noise must be minimized. The heat dissipation of the arrays also has to be minimized. To meet these requirements and achieve the best performance of the arrays, we optimized the array driving clocks, the bias voltage, and the supply currents, and evaluated the temperature dependence of the performance. In particular, we found that the voltage between the gate and source of the FET of the multiplexer SBRC-189 had a strong dependence on temperature. This effect becomes a dominant source for the noise unless the temperature is kept within 20mK. We have achieved the readout noises of about 30e^- and 40e^- with the correlated double sampling for the flight model readout circuits of the InSb and Si:As arrays, respectively. These noises ensure that the background-limited performance can be achieved for the observations of IRC in the 4-26μm range in the current observing scheme. In addition, we are now planning to make scan mode observations by IRC. We have developed a new operation way of the arrays to achieve the stable response and low readout noise in the scanning operation for the first time. The IRC is now installed in the flight model cryostat and the first end-to-end test has just been completed. We report on the expected performance of the IRC together with the array test results.

Mechanical cryocoolers represent a significant enabling technology for NASA's Earth and Space Science Enterprises. Over the years, NASA has developed new cryocooler technologies for a wide variety of space missions. Recent achievements include the NCS, AIRS, TES and HIRDLS cryocoolers, and miniature pulse tube coolers at TRW and Lockheed Martin. The largest technology push within NASA right now is in the temperature range of 4 to 10 K. Missions such as the Next Generation Space Telescope (NGST) and Terrestrial Planet Finder (TPF) plan to use infrared detectors operating between 6-8 K, typically arsenic-doped silicon arrays, with IR telescopes from 3 to 6 meters in diameter. Similarly, Constellation-X plans to use X-ray microcalorimeters operating at 50 mK and will require ~6 K cooling to precool its multistage 50 mK magnetic refrigerator. To address cryocooler development for these next-generation missions, NASA has initiated a program referred to as the Advanced Cryocooler Technology Development Program (ACTDP). This paper presents an overview of the ACTDP program including programmatic objectives and timelines, and conceptual details of the cooler concepts under development.

High performance, low temperature cryocoolers are being developed for future space-borne telescopes and instruments. To meet mission objectives, these coolers must be compact, lightweight, have low input power, operate reliably for 5-10 years, and produce no disturbances that would affect the pointing accuracy of the instruments. This paper describes progress in the development of turbo-Brayton cryocoolers addressing cooling in the 5 K to 20 K temperature range for loads of up to 300 mW. The key components for these cryocoolers are the miniature, high-speed turbomachines and the high performance recuperative heat exchangers. The turbomachines use gas-bearings to support the low mass, high speed rotors, resulting in negligible vibration and long life. Precision fabrication techniques are used to produce the necessary micro-scale geometric features that provide for high cycle efficiencies at these reduced sizes. Turbo-Brayton cryocoolers for higher temperatures and loads have been successfully developed for space applications. For efficient operation at low temperatures and capacities, advances in the core technologies have been pursued. Performance test results of a new, low poer compressor will be presented, and early cryogenic test results on a low temperature expansion turbine will be discussed. Projections for several low temperature cooler configurations are summarized.

The Space Infrared Telescope Facility (SIRTF) is the last of NASA's four great observatories, scheduled for launch in January 2003. At the heart of the SIRTF Observatory is the Cryogenic Telescope Assembly (CTA) that provides a 1.4 K heat sink for the SIRTF Science Instruments while cooling the telescope to as low as 5.5 K in order to achieve thea low photon background. This unique cryogenic/thermal system provides the necessary cooling through passive means combined with vapor cooling by the helium gas vented from a 360 liter superfluid helium cryostat. The passive cooling is made possible by the favorable thermal environment achieved in an Earth-trailing solar orbit, with the payload millions of miles from the Earth. The SIRTF Cryostat and integrated CTA have just completed an extended period of cryogenic system performance testing. This testing included mission lifetime assessment, luanch hold capability and in situ characterization and performance measurements of the porous plug liquid-vapor phase separator. We also encountered and recovered from an ice contamination incident within the cryostat. We report here the system and component test results. We also provide recommendations and lessons learned through the operations of the SIRTF system.

The Next Generation Sky Survey (NGSS) is a Medium Explorer currently in Phase A study, with launch planned for 2007. NGSS will map the entire sky with unprecedented sensitivity from 3.5 to 23 microns. With over 500,000 times the sensitivity of COBE at 3.5 and 4.7 microns, and a thousand times that of IRAS at 12 and 25 microns, NGSS will establish an essential database for testing theories of the origins of planets, stars, and galaxies, and is the necessary precursor for NGST. The science objectives of NGSS include finding the most luminous galaxies in the universe, and the closest stars to the sun. NGSS will achieve these dramatic advances while minimizing mission cost and risk by using flight-proven technology for its spacecraft bus components and cryogenic instrument, as well as 2MASS data processing software.

This paper presents a description of the Hubble Space Telescope (HST) Near Infrared Camera and Multi Object Spectrometer (NICMOS) Cooling System (NCS), the cutting edge technology involved, a comparison of predicted versus on-orbit thermal performance, as well as possible future space applications. The NCS hardware consists of the NICMOS Cryogenic Cooler (NCC), an Electronics Support Module (ESM), a Capillary Pumped Loop (CPL)/Radiator assembly, and associated interface harnessing. The NCC is a state-of-the-art reverse Turbo-Brayton cycle mechanical cooler employing micro turbo machinery, driven by advanced power conversion electronics, operating at speeds up to 450,000 revolutions per minute to remove heat from the NICMOS instrument. The ESM provides command, control, and power distribution to the NCS, as well as providing the primary interface to the existing HST electronics. A two-phase CPL system removes heat from the NCC and transfers it to the radiator mounted externally on the HST aft shroud. The system was installed during Servicing Mission 3B via extravehicular activities in March 2002. The NCS revived the NICMOS instrument, which experienced a reduced operational lifetime due to an internal thermal short in its dewar structure, and restored HST scientific infrared capability to operational status.

The High Resolution Airborne Wideband Camera (HAWC) and the Submillimeter And Far Infrared Experiment (SAFIRE) will use identical Adiabatic Demagnetization Refrigerators (ADR) to cool their detectors to 200mK and 100mK, respectively. In order to minimize thermal loads on the salt pill, a Kevlar® suspension system is used to hold it in place. An innovative, kinematic suspension system is presented. The suspension system is unique in that it consists of two parts that can be assembled and tensioned offline, and later bolted onto the salt pill.

Large astronomical Gossamer telescopes in space will need to employ large solar shields to safeguard the optics from solar radiation. These types of telescopes demand accurate controls to maintain telescope pointing over long integration periods. We propose an active solar shield system that harnesses radiation pressure to accurately slew and acquire new targets without the need for reaction wheels or thrusters. To provide the required torques, the solar shield is configured as an inverted, 4-sided pyramidal roof. The sloped roof interior surfaces are covered with hinged “tiles” made from piezoelectric film bimorphs with specular metallized surfaces. Nominally, the tiles lie flat against the roof and the sunlight is reflected outward equally from all sloped surfaces. However, when the tiles on one roof pitch are raised, the pressure balance is upset and the sunshade is pushed to one side. By judicious selection of the tiles and control of their lift angle, the solar pressure can be harvested to stabilize the spacecraft orientation or to change its angular momentum. A first order conceptual design performance analysis and the results from the experimental design, fabrication and testing of piezoelectric bimorph hinge elements will be presented. Next phase challenges in engineering design, materials technology, and systems testing will be discussed.

SPICA (SPace Infrared telescope for Cosmology and Astrophysics) is a future infrared astronomy mission which is now under study in Japan. Larger aperture (~ 3.5m) infrared telescope will be launched into L2 halo orbit at ambient temperature, and will be cooled in orbit by mechanical cooler down to 4.5K. SPICA is powerful in mid and far infrared observations and will delineate the birth and evolution of galaxies, stars and planetary systems which will play a complementary role to NGST and Hershell.

Development of large, far-infrared telescopes in space has taken on a new urgency with breakthroughs in detector technology and recognition of the fundamental importance of the far-infrared spectral region to cosmological questions as well as to understanding how our own Solar System came into being. SAFIR is 10m-class far-infrared observatory that would begin development later in this decade to meet these needs. Its operating temperature (T ≤ 4 K) and instrument complement would be optimized to reach the natural sky confusion limit in the far-infrared with diffraction-limited peformance down to at least the atmospheric cutoff, λ ⪆ 40 μm. This would provide a point source sensitivity improvement of several orders of magnitude over that of SIRTF. SAFIR's science goals are driven by the fact that youngest stages of almost all phenomena in the universe are shrouded in absorption by and emission from cool dust that emits strongly in the far-infrared, 20 μm - 1mm. The main drivers on the telescope are operating temperature and aperture. SAFIR can take advantage of much of the technology under development for NGST. Because of the much less stringent requirements on optical accuracy, however, SAFIR can be developed at substantially lower cost.

CIVA/Mars is a space miniaturized spectral imaging microscope. It is designed to in-situ analyze samples on Mars surface. It requires the use of a double cooling system : a passive cooling for the global instrument which will be maintained at a temperature higher than 160 K and an active cooling system for the IR MCT detector matrix which must be maintained at a temperature lower than 140 K. Taking into account the mission constraints, a trade-off analysis of available active cooling systems led to the choice of a thermoelectrical cooler (TEC). Space validation tests of standard multi-stage TECs were performed. Performances did not meet the technical specifications of the instrument. Two types of customized TEC modules were then designed and manufactured : mechanical prototypes from RMT Ltd. and optimized modules from Marlow Ind. A first RMT prototype passed the vibration & shock qualification tests and a second passed the low temperatures vacuum qualification tests with few margins. A Marlow optimized module passed the low temperatures vacuum qualification tests; its characteristics and performances make it compatible with CIVA/Mars. In this paper, the instrument mission and characteristics are first presented. Then TEC design studies are discussed. Finally, optimized TEC space qualification tests are detailed, and the performances analyzed.

"To take the next step in exploring this important part of the spectrum [30-300μm], the committee recommends the Single Aperture Far-Infrared Observatory (SAFIR)." - Astronomy and Astrophysics in the New Millennium, 2001. In response to this recommendation, we have undertaken a study of the enabling technologies for a large single aperture far-infrared telescope such as SAFIR. A broad list of science investigations was produced and used to generate an explicit list of science requirements, from which top-level engineering requirements were derived. From these requirements, we developed a conceptual design for the SAFIR observatory based on NGST's current designs. A detailed analysis has been made of the changes and technologies necessary to produce SAFIR. Crucial technologies requiring innovation include lightweight deployable optics, cryogenic cooling of optical elements and instruments, and large arrays of sensitive detectors. Cryogen-free refrigeration technologies are necessary for SAFIR's long mission lifetime, and will have to provide significant (~100mW) cooling power at 4K to cool the mirrors while providing very low temperatures (~50mK) for detector arrays. The detector arrays require wide wavelength coverage, thousands of continuum elements, and compatibility with broadband and spectroscopic instruments.

PRIME (The Primordial Explorer) is a proposed Explorer-class mission. It will carry out a deep sky survey from space in four near-infrared bands between ~0.9-3.5 μm. It surveys a quarter of the sky to AB magnitude of ~24, which is ~600 times deeper than 2MASS and ~ five million times deeper than COBE at long wavelengths. Deeper surveys in selected sky regions are also planned. PRIME will reach an epoch during which the first quasars, galaxies and clusters of galaxies were formed in the early universe, map the large-scale structure of the dark matter, discover Type-Ia supernovae to be used in measuring the acceleration of the expanding universe, and detect thousands of brown dwarfs and even Jupiter-size planets in the vicinity of the solar system. Most of these objects are so rare that they may be identified only in large and deep surveys. PRIME will serve as the precursor for the Next Generation Space Telescope (NGST), supplying rare targets for its spectroscopy and deep imaging. It is more than capable of providing targets for the largest ground-based telescopes (10-30m). Combining PRIME with other surveys (SDSS, GALEX) will yield the largest astronomical database ever built.

The discovery of galaxies beyond z~1 which emit the bulk of their luminosity at long wavelengths has demonstrated the need for high-sensitivity, broad-band spectroscopy in the far-IR/submm/mm bands. Because many of these sources are not detectable in the optical, long-wavelength spectroscopy is key to measuring their redshifts and ISM conditions. The continuum source list will increase in the coming decade with new ground-based instruments (SCUBA2, Bolocam, MAMBO), and the surveys of HSO and SIRTF. Yet the planned spectroscopic capabilities lag behind, in part due to the difficulty in scaling existing IR spectrograph designs to longer wavelengths. To overcome these limitations, we are developing WaFIRS, a novel concept for long-wavelength spectroscopy which utilizes a parallel-plate waveguide and a curved diffraction grating. WaFIRS provides the large (~60%) instantaneous bandwidth and high throughput of a conventional grating system, but offers a dramatic reduction in volume and mass. WaFIRS requires no space overheads for extra optical elements beyond the diffraction grating itself, and is two-dimensional because the propagation is confined between two parallel plates. Thus several modules could be stacked to multiplex either spatially or in different frequency bands. The size and mass savings provide opportunities for spectroscopy from space-borne observatories which would be impractical with traditional spectrographs. With background-limited detectors and a cooled 3.5 m telescope, the line sensitivity would be comparable to that of ALMA, with instantaneous broad-band coverage. We present the spectrometer concept, performance verification with a mm-wave prototype, and our progress toward a cryogenic astronomical instrument

The Astrobiology Explorer (ABE) is a MIDEX mission concept, currently under Concept Phase A study at NASA's Ames Research Center in collaboration with Ball Aerospace & Technologies, Corp., and managed by NASA's Jet Propulsion Laboratory. ABE will conduct infrared spectroscopic observations to address important problems in astrobiology, astrochemistry, and astrophysics. The core observational program would make fundamental scientific progress in understanding the distribution, identity, and evolution of ices and organic matter in dense molecular clouds, young forming stellar systems, stellar outflows, the general diffuse ISM, HII regions, Solar System bodies, and external galaxies. The ABE instrument concept includes a 0.6 m aperture Ritchey-Chretien telescope and three moderate resolution (R = 2000-3000) spectrometers together covering the 2.5-20 micron spectral region. Large format (1024 x 1024 pixel) IR detector arrays will allow each spectrometer to cover an entire octave of spectral range per exposure without any moving parts. The telescope will be cooled below 50 K by a cryogenic dewar shielded by a sunshade. The detectors will be cooled to ~7.5 K by a solid hydrogen cryostat. The optimum orbital configuration for achieving the scientific objectives of the ABE mission is a low background, 1 AU Earth driftaway orbit requiring a Delta II launch vehicle. This configuration provides a low thermal background and allows adequate communications bandwidth and good access to the entire sky over the ~1.5 year mission lifetime.

We introduce a Japanese future plan of the IR space astrometry(JASMINE-project). JASMINE is an infrared(K-band) scanning astrometric satellite. JASMINE(I and/or II-project) is planned to be launched between 2013 and 2015 and will measure parallaxes, positions and proper motions with the precision of 10 microarcsec at K=12~14mag. JASMINE can observe about a few hundred million stars belonging to the disk and the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Furthermore JASMINE will also measure the photometries of stars in K, J and H-bands. The main objective of JASMINE is to study the fundamental structure and evolution of the disk and the bulge components of the Milky Way Galaxy. Furthermore its important objective is to investigate stellar physics.

A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment. The goal is to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper. The spectrograph concept is optimized to have very high efficiency and low spectral resolution (R~100), constant through the wavelength range (0.35-1.7μm), adapted to the scientific goals of the mission.

Planck, scheduled for launch in 2007, will be the third space mission to observe the cosmic microwave background (CMB). Two cryogenic instruments and an off-axis telescope will provide an unprecedented combination of sensitivity, angular resolution, and frequency coverage. Planck is designed to measure the temperature anisotropies of the CMB to limits set not by the instruments, but rather by the Universe itself. In addition, it will measure the E-type polarization of the CMB, and provide all-sky surveys at nine frequencies between 30 and 857 GHz.