The James Webb Space Telescope (JWST) is the scientific successor to both the Hubble Space Telescope and the Spitzer Space Telescope. It is envisioned as a facility-class mission. The instrument suite provides broad wavelength coverage and capabilities aimed at four key science themes: 1)The End of the Dark Ages: First Light and Reionization; 2) The Assembly of Galaxies; 3) The Birth of Stars and Protoplanetary Systems; and 4) Planetary Systems and the Origins of Life. NIRCam is the 0.6 to 5 micron imager for JWST, and it is also the facility wavefront sensor used to keep the primary mirror in alignment.

NIRCam is a highly sensitive, multi-spectral, high-resolution, cryogenic, compact, light-weight, and rugged near infra-red camera on the James Webb Space Telescope. The successful development of NIRCam is aided by good system engineering practice. This is a discussion of important elements of NIRCam System Engineering with some light-hearted contrast to a more common activity.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 37 kelvins to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition NIRCam is used as a metrology instrument during the JWST observatory commissioning on orbit, during the initial and subsequent precision alignments of the observatory's multiple-segment 6.3 meter primary mirror. JWST is scheduled for launch and deployment in 2012. This paper is an overview of the NIRCam instrument with pointers to several NIRCam subsystem papers to be presented in the same conference. This paper will introduce and explain at top level the structural, optical, mechanical and thermal subsystems of NIRCam.

The Near Infrared Camera (NIRCam) for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 32 to 37 K to produce high resolution images in two wave bands encompassing the range from λ = 0.6 to 5.0 microns. In addition NIRCam is used as a metrology instrument for the JWST observatory, providing critical data for alignment of the observatory's multiple-segment 6.3 meter primary mirror. JWST is scheduled for launch and deployment in 2012. This paper is an overview of the NIRCam instrument's optical hardware and performance. Detailed discussions of specific subassemblies will be presented in other papers in the same conference.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments to be installed into the Integrated Science Instrument Module (ISIM) on JWST. NIRCam's requirements include operation at 37 Kelvin to produce high-resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition, NIRCam is to be used as a metrology instrument during the JWST observatory commissioning on orbit, during the precise alignment of the observatory's multiple-segment primary mirror. This paper will present the optical analyses performed in the development of the NIRCam optical system. The Compound Reflectance concept to specify coating on optics for ghost image reduction is introduced in this paper.

The Near Infrared Camera is the primary imaging instrument on the James Webb Space Telescope. This instrument operates in the wavelength range of 0.6 to 5 microns and at a temperature of 35K. Two mirror-image optical paths or modules are utilized to provide two adjacent fields of view for science observations and redundancy for the purpose of wavefront sensing. All optical components are supported and aligned by an Optical Bench Assembly consisting of two benches mounted back to back. Each optical bench is a closed back Beryllium structure optimized for mass and stiffness. The closed back structure is achieved by bonding two machined parts together at the midplane of the structure. Each bench half is an open back structure consisting of a facesheet with machined ribs optimized to provide stiffness and to support along primary load paths. The two benches are integrated with optical components separately and are subsequently joined by bolts and pins to form the Optical Bench Assembly. The assembly is then mounted to interface struts, which are used to mount the instrument within the Integrated Science Instrument Module for integration into the JWST observatory. The design of the Optical Bench Assembly is describing including trade studies and analysis results.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five-year mission lifetime. NIRCam's requirements include operation at 37 kelvins to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition NIRCam is used as a metrology instrument during the JWST observatory commissioning on orbit, during the initial and subsequent precision alignments of the observatory's multiple-segment 6.3 meter primary mirror. JWST is scheduled for launch and deployment in 2012. This paper is an overview of the NIRCam instrument's Optical Calibration Sources (Flat Field and Point Source). It will discuss the source requirements and will explain the optical and electronic technology developed to fulfill their mission requirements.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 37 kelvins (K) to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition NIRCam is used as a metrology instrument during the JWST observatory commissioning on orbit, during the initial and subsequent precision alignments of the observatory's multiple-segment 6.3 meter primary mirror. This paper describes some preliminary performance results of prototype coronagraph masks.

The Near InfraRed Camera (NIRCam) for the James Webb Space Telescope (JWST) is a refracting camera system. Its unique performance derives from the Lithium Fluoride, Barium Fluoride and Zinc Selenide lenses that provide aberration and color correction over the large operating wavelength. This paper describes the optical prescription, lens materials and prototype characterization for the camera lenses.

This paper describes the design of the compact, lightweight, and athermalized Pick Off Mirror and Mount as well as similar mounts for other NIRCam fold mirrors, including the Focal Plane Assembly Fold Mirror Mount. Structural and thermal analysis as well as actual prototype testing is also described.

The NIRCam instrument will provide near-infrared imaging capabilities for the James Webb Space Telescope. In addition, this instrument contains the wavefront-sensing elements necessary for optimizing the performance of the primary mirror. Several of these wavefront-sensing elements will reside in the NIRCam Filter Wheel Assembly. The instrument and its complement of mechanisms and optics will operate at a cryogenic temperature of 35K. This paper describes the design of the NIRCam Filter Wheel Assembly.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space telescope (JWST) is one of four science instruments to be installed into the integrated science instrument module (ISIM) on JWST for the purpose of conducting scientific observations over a five year mission lifetime. NIRCam is required to operate at 37 Kelvin to produce high resolution images in two-wave bands ranging from 0.6 to5 microns. A relatively recent requirement for the NIRCam instrument is to provide a means of imaging the primary mirror for ground testing, instrument commissioning, and diagnostics throughout the mission. This paper discusses the development of the pupil imaging lens (PIL) assembly. In addition to detailing the driving requirements, this paper briefly covers the mechanism design and delves more deeply into the engineering of the optical design.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments to be installed into the Integrated Science Instrument Module (ISIM) on JWST. NIRCam's requirements include operation at 37 Kelvin to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition, NIRCam is to be used as a metrology instrument during the JWST observatory commissioning on orbit, during the precise alignment of the observatory's multiple-segment primary mirror. This paper will describe the NIRCam Thermal subsystem design for stable operation at 37 Kelvin.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 37 kelvins (K) to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition NIRCam is used as a metrology instrument during the JWST observatory commissioning on orbit, during the initial and subsequent precision alignments of the observatory's multiple-segment 6.3 meter primary mirror. This paper describes the integration and test (I&T) processes used to verify the Imaging Optical Assembly (IOA) to the defined requirements.

This paper describes two cryogenic thermal switches (CTSWs) under development for instruments on the James Webb Space Telescope (JWST). The first thermal switch was designed to extend the life of the solid H2 dewar for the 6 K Mid Infrared Instrument (MIRI) while the second thermal switch is needed for contamination and over-temperature control of three 35 K instruments on the Integrated Science Instrument Module (ISIM). In both cases, differential thermal expansion (DTE) between two materials having differing CTE values is the process that underpins the thermal switching. The patented DTE-CTSW design utilizes two metallic end-pieces, one cup-shaped and the other disc-shaped (both MIRI end-pieces are Al while ISIM uses an Al/Invar cup and an Al disc), joined by an axially centered Ultem rod, which creates a narrow, flat gap between the cup (rim) and disc. A heater is bonded to the rod center. Upon cooling one or both end-pieces, the rod contracts relative to the end-pieces and the gap closes, turning the CTSW ON. When the rod heater is turned on, the rod expands relative to the end-pieces and the gap opens, turning the CTSW OFF. During testing from 6-35 K, ON conductances of 0.3-12 W/K and OFF resistances greater than 2500 K/W were measured. Of particular importance at 6 K was the Al oxide layer, which was found to significantly decrease DTE-CTSW ON conductance when the mating surfaces were bare Al. When the mating surfaces were gold-plated, the adverse impact of the oxide layer was mitigated. This paper will describe both efforts from design through model correlation.

A cryogenic thermal vacuum testing facility at NASA's Goddard Space Flight Center (GSFC) was developed to determine thermal control coating emittance at cryogenic temperature for the JWST/ISIM project. In order to meet ISIM thermal requirements in design and analysis accurate knowledge of material and optical properties as a function of temperature for the assembly are required. The optical property data currently available in this temperature regime have a relatively large (30-50%) uncertainty associated with the measurements. In an effort to reduce these uncertainties the 'ISIM Thermal Control Coating Cryogenic Emittance Tests' (3 performed to date) were developed utilizing this facility. The objective of these tests was to determine the emittance of candidate thermal control coatings and radiator geometric configurations for the ISIM over the temperature range from 30K to 150K while minimizing associated uncertainty. This paper presents the testing approach, experimental methods, and results for the emittance tests performed in the GSFC cryogenic facility to date. Challenges encountered during this testing effort included quantifying parasitic heat losses/gains to a high degree of accuracy in an effort to minimize associated measurement uncertainty.

NASA's James Webb Space Telescope-Integrated Science Instrument Module (JWST-ISIM) radiators and structures operate in the 30 to 40 K range. There is limited emittance data for coatings of interest in this temperature range. Calorimetric emittance tests performed at Goddard Space Flight Center in the past have used a transient technique, which results in large uncertainties (typically > +/-30%) at the lowest temperatures. These large uncertainties would practically require use of overly conservative emissivities in radiator sizing, which would in turn pose unnecessary area and mass penalties. There is thus a strong incentive to make highly accurate emittance measurements. A special liquid helium cryogenic facility was fabricated for this purpose, and a series of thermal balance tests were subsequently performed at NASA/GSFC to measure the emittance of selected ISIM coatings accurately at temperatures down to 25K. This paper discusses the test methodology, and the analytical methods used to calculate the emittance and its accuracy from the measured data. Preliminary results show that for relatively high emittance coatings, typical measurement accuracies at 30 K approach +/- 5%.

The MIR-L is the mid-IR (12-26 μm) instrument for Japanese infrared astronomical satellite, the ASTRO-F. The instrument has 2 observing modes: a wide field imaging mode with a field of view of 10.7 × 10.2 arcmin² and a low resolution spectroscopic mode with a spectral resolution R = λ/Δλ about 20. The spectroscopic mode provides with not only slit-spectroscopy for extended sources but also slitless-spectroscopy for point sources. We describe here the design, manufacturing, and performance evaluation of the cryogenic optical system of the MIR-L. The concept of the optical system design is to realize wide field observations with a compact size. The instrument employs a refractive optics of 5 lenses (CsI - CsI - KRS-5 - CsI - KRS-5) with a 256×256 pixel Si:As IBC array detector, 3 filters, and 2 grisms. The refractive indices of CsI and KRS-5 at the operating temperature of about 6 K have ambiguities because of the difficulty of the measurements. We therefore designed the MIR-L optics with tolerances for the uncertainties of the indices. Since both CsI and KRS-5 have the fragility and the large thermal expansion, we designed a specialized mounting architecture to prevent from making damages and/or decentrations of the lenses at cryogenic temperatures under the serious vibration during the launch. As a result, the optical system of the MIR-L has passed both vibration and thermal cycle tests without damage and performance degradation, and achieved diffraction limited performance over its full wavelength range at the operating temperature.

The Wide Field Infrared Survey Explorer is a NASA Medium Class Explorer mission to perform and all-survey in four infrared wavelength bands. The science payload is a cryogenically cooled infrared telescope with four 1024² infrared focal plane arrays covering from 2.8 to 26 microns. Advances in focal plane technology and a large aperture allow an all-sky survey to be performed with high sensitivity and resolution. Mercury cadmium telluride (MCT) detectors, cooled to 32 K, are used for the two midwave channels, and Si:As detectors, cooled to < 8.3 K, are used for the two long wavelength channels. Cooling for the payload is provided by a two-stage solid hydrogen cryostat providing temperatures <17K and < 8.3K at the telescope and Si:As focal planes, respectively. The science payload supports operations on orbit for the seven month baseline mission with a goal to support a 13 month extended mission if available. This paper provides a payload overview and discusses instrument requirements and performance.

The Wide-field Infrared Survey Explorer (WISE) instrument includes a cryogenic telescope, scanner, and imaging optics module that provides four channels of infrared imaging between 2.8 and 26 microns. The telescope is a 40 cm aperture reflecting five-mirror imager/collimator relay that provides 8X demagnification, a 47 x 86 arcminute field of regard, and a real exit pupil for scanning. It also provides distortion control to better than one part in a thousand to prevent image blur during internal scanning. A one-axis scan mirror at the exit pupil scans the detectors' field-of-view across the telescope field-of-regard, countering the orbital motion and freezing the line of sight during the multi-second exposure period. The imaging optics module is a five-mirror re-imager with dichroic beamsplitters that separate the energy into four channels. All modules operate below 17 Kelvin. The all-reflective system uses aluminum mirrors and metering structures. The scanner is a derivative of the SPIRIT III scanner flown previously. WISE has been selected by NASA for Phase B design.

The NIRSpec instrument on the James Webb Space Telescope (JWST) is a multi-object spectrograph capable of measuring the near infrared spectrum of at least 100 objects simultaneously at various spectral resolutions. It operates under cryogenic conditions (T~ 35 K). NIRSpec is part of the JWST science instruments suite. Its main purpose is to provide low (R=100), medium (R=1000) and high resolution (R=2700) spectroscopic observations over the wavelength range 0.6 μm - 5.0 μm in support of the four JWST science programs. The NIRSpec instrument is being developed by the European Space Agency with EADS Astrium Germany GmbH as the prime contractor.

A second generation near-infrared instrument was built by the University of Colorado for the ARC 3.5 meter telescope and is being commissioned at the Apache Point Observatory. An initial engineering run, first light, commissioning observations, and initial facility science operations have been accomplished in the last year. Instrument imaging performance was good to excellent from first light and consortium observers began to employ the instrument on a shared-risk basis immediately after commissioning operations. Instrument optical and mechanical performance during this testing and operations phase are discussed. Detector system (Rockwell Hawaii-1RG 1024x1024 HgCdTe focal plane array with Leach controller) characteristics during these early operations are detailed along with ongoing efforts for system optimization. High resolution (R~10,000) spectroscopy is planned employing a Queensgate (now IC Optical) cryogenic Fabry-Perot etalon, though mechanical difficulties with the etalon precluded a system performance demonstration. The Consortium has decided that the instrument will retain the name NIC-FPS (Near Infrared Camera and Fabry-Perot Spectrometer) after commissioning.

Single crystal Lithium Fluoride (LiF) has been base-lined as one of the optical materials for the Near Infra-Red Camera (NIRCam) on the James Webb Space Telescope (JWST). Optically, this material is outstanding for use in the near IR. Unfortunately, it has poor mechanical properties that make it very difficult for use in any appreciable size on cryogenic space based instruments. In addition to a dL/L from 300K to 30K of ~-0.48% and room temperature CTE of ~37ppm/K, LiF deforms plastically under relatively small stresses. This paper will discuss the heritage of LiF in space-based systems and summarize the mechanical and thermal material data for LiF that is available in the literature. New data will be presented relative to a design limit load for the material so that designers can use this material for space flight applications. Additional new data relative to the cryogenic index of refraction of the material over the near infrared is also provided.

The refractive optical design of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) uses three infrared materials in its lenses: LiF, BaF₂, and ZnSe. In order to provide the instrument's optical designers with accurate, heretofore unavailable data for absolute refractive index based on actual cryogenic measurements, two prismatic samples of each material were measured using the cryogenic, high accuracy, refraction measuring system (CHARMS) at NASA's Goddard Space Flight Center (GSFC), densely covering the temperature range from 15 to 320 K and wavelength range from 0.4 to 5.6 microns. Data reduction methods are discussed and graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient for these three materials are presented for selected wavelengths and temperatures along with estimates of index uncertainty. Coefficients for temperature-dependent Sellmeier fits of measured index are also presented with an example of their usage to predict absolute index at any wavelength or temperature within the applicable range of those parameters.

The Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center has been enhanced in a number of ways in the last year to allow the system to accurately collect refracted beam deviation readings automatically over a range of temperatures from 15 K to well beyond room temperature with high sampling density in both wavelength and temperature. The engineering details which make this possible are presented. The methods by which the most accurate angular measurements are made and the corresponding data reduction methods used to reduce thousands of observed angles to a handful of refractive index values are also discussed.

We report cryogenic optical properties of Cd_0.96Zn_0.04Te wafers that are used as substrate layers in the manufacturing of HgCdTe focal-plane array detectors. These studies are motivated by the fact that the substrate optical properties influence the overall detector performance. The studies consist of measuring the substrate frequency dependent transmittance T(ω) and reflectance R(ω) above and below the optical band-gap in the UV/Visible and infrared frequency ranges, and with temperature variation of the sample from 5 to 300 K. Analysis of these data shows the index of refraction n shows slight dispersion in the transparent 1-6 μm range of CdZnTe. Furthermore, n exhibits a weak reduction in the average value (~ 4%) when the sample temperature is reduced from 300 K to 5 K. These measurements also show that the optical gap near 1.49 eV at 300 K increases to 1.62 eV at 5 K. Finally, we observe sharp absorption peaks near this gap energy at low temperatures. The close proximity of these peaks to the optical transition threshold suggests that they originate from the creation of bound electron-hole pairs or excitons. The decay of these excitonic absorptions may contribute to a photoluminescence and transient background response of these back-illuminated HgCdTe CCD detectors.

The ground testing of a sensor system under flight conditions is fundamental to characterizing its performance. It should be accomplished early and often in order to manage operational uncertainty and reduce system life-cycle cost. As a DoD Major Range Test Facility Base (MRTFB), the Arnold Engineering Development Center (AEDC) provides a comprehensive capability that strives to ensure system performance evaluations that are not limited by test infrastructure. For over 30 years, the space chambers at AEDC have performed space-sensor characterization, calibration, and mission simulation testing on space-based, interceptor, and airborne sensors. In partnership with Missile Defense Agency (MDA), capability upgrades are continuously pursued to keep pace with evolving sensor technologies. A critical aspect of these chambers is the quality of the mirror coatings used to project simulated target scenes to the unit under test in low-background cryogenic conditions. This paper discusses the recent effort at AEDC to refurbish and/or replace the mirror collimating systems in their 7V and 10V Aerospace Chambers and the coating choices that have been considered.

This report describes the facility and experimental methods at the Goddard Space Flight Center Optics Branch for the measurement of the surface figure of cryogenically-cooled spherical mirrors using standard phase-shifting interferometry, with a standard uncertainty below 2nm rms. Two developmental silicon carbide mirrors were tested: both were spheres with radius of curvature of 600 mm, and clear apertures of 150 mm. The mirrors were cooled within a cryostat, and the surface figure error measured through a fused-silica window. The GSFC team developed methods to measure the change in surface figure with temperature (the cryo-change) with a combined standard uncertainty below 1 nm rms. This paper will present the measurement facility, methods, and uncertainty analysis.

A key instrument for an Extremely Large Telescope (ELT) is likely to be multi-object spectrometer which observes at least 100 discrete sources with diffraction limited spatial resolution and moderate spectral resolution in the wavelength region from 1.0 to 2.5 μm. Such an instrument has been chosen as the principal driver for the Smart Focal Planes technology development project which has brought together 14 companies and institutes in Europe and Australia. An overview of a new ELT instrument concept based upon beam manipulators (including novel 'starbug' miniature robots) is presented; supported by a summary of scientific goals and systems requirements. Progress made on specific support technology studies is also presented, including work on image slicer replication and cryogenic reconfigurable slits.

Traditionally, focal plane arrays require extensive external focal plane electronics (FPE) to provide clocks and biases as well as to digitize the analog output signals. The FPE has to be well-designed and is typically large, heavy and powerhungry. Most importantly, the FPE has to be placed some distance away from the FPA, which complicates maintaining low noise performance throughout the complete system. To offer an alternative to the discrete electronics, Rockwell Scientific has developed a new approach known as the SIDECAR application-specific integrated circuit (ASIC). This single chip provides all the functionality necessary to operate an infrared array with the convenience of a pure digital interface to the outside world. This paper will present performance data on the latest generation of the SIDECAR ASIC operating the JWST H2RG detector arrays at cryogenic temperature. The test results demonstrate that an ASIC based FPA system will meet or exceed all performance requirements for the JWST mission. The SIDECAR ASIC has been selected by NASA to become the FPA drive electronics for all shortwave infrared instruments on JWST.

Upcoming far-IR space missions are faced with a very challenging requirement: to make detectors with sufficient sensitivity to be limited by the photon noise present in the darkness of space. At long wavelengths (>100μm), where the Zodiacal light is insignificant and the sky brightness corresponds to only ~100 aW, detectors must have noise equivalent powers of <10-19 W/√Hz. For fundamental reasons, this can only be achieved with detectors operating at about 20 mK, giving rise to the need for refrigerators capable of operating as low as 10 mK. Only adiabatic demagnetization refrigerators (ADR) have demonstrated both zero-g operation and the capacity for cooling into this regime. Over the last few years we have developed a multi-stage ADR that can produce continuous cooling at temperatures of 35 mK or lower, and have recently begun developing additional stages that will push the operating range below 10 mK. Our prototype device uses a 4.2 K heat sink, but it can easily work with pulse-tube or Gifford-McMahon cryocoolers. We describe the design, operation and capabilities of the ADR, as well as the cryogen-free dewar that will be used for performance tests.

An innovative cryocooler is under development that promises to provide high efficiency 4K-10K cooling for space-based focal plane arrays. It is based upon a novel modification of the Collins cycle, which is commonly used in large-scale high-efficiency terrestrial cryogenic machines. Cryogenic machines based on the conventional Collins or Brayton cycles routinely operate with input powers of about 740 Watts per Watt of refrigeration at 4K. Currently available small-scale cryocoolers capable of about 1W of cooling at 4K typically require 5kW - 7.5kW per Watt of cooling. Microelectronic technology is employed in the modified cycle to enable a reduction in scale and mechanical complexity while retaining the high efficiency potential of the conventional Collins cycle. The modified Collins cycle is a continuous, or DC, flow device. This eliminates the need for the costly exotic alloys used in the regenerators of periodic, or AC, flow pulse-tube and Stirling type cryocoolers. It also permits separation of the cryocooler cold head from the load without a significant thermodynamic penalty, thereby enabling vibration isolation and the potential for improved system integration. An engineering prototype is currently undergoing development testing to demonstrate the potential of this concept to provide cooling at 10K and below. This paper will present the major design concepts employed in the engineering prototype, the results of initial engineering prototype development testing, as well as a discussion of the benefits of this approach and the anticipated space-based and terrestrial applications.

This paper describes the design, manufacturing, modeling, and testing of a methane cryogenic diode heat pipe (CDHP) thermal switching system for the CRISM instrument onboard the NASA/JPL Mars Reconnaissance Orbiter. The purpose of the CDHP system is to enable three 1-year cryocoolers to provide 2 years of cooling to the 100 K CRISM sensor while minimizing the parasitic heat input from the two OFF (redundant) cryocoolers. Without the CDHP system, the parasitic heat input from the two OFF cryocoolers would prevent the CRISM sensor from being cooled to an acceptably low operating temperature. To provide sufficient structural support for launch with low parasitic heat input, the three methane CDHPs were supported by small diameter Kevlar tension cables attached to a shoebox-shaped cold shroud that enveloped the assembly. The cold shroud -- thermally coupled by a flexible link to the (cryoradiator cooled) cold side of the instrument housing -- was suspended from the warm side of the instrument housing by a second set of Kevlar cables, creating a dual-nested Kevlar cable thermal isolation/structural support system similar to that flown on the CRYOTSU flight experiment on STS-95. To accurately test the thermal switching system, a novel laboratory set-up was utilized involving three parallel heat metering cryocooler simulators (Q-meters). Numerous test runs were carried out to evaluate the impact of various system operating parameters. The parasitic heat leak predictions corresponded very closely to the measured data. The paper describes the effort from concept development through test data analysis.

The James Webb Space Telescope (JWST) program have identified the need for cryogenic cooling transport devices that (i) provide robust/reliable thermal management for Infrared (IR) sensors/detectors in the temperature range of 20-30K, (ii) minimize vibration effects of mechanical cryocoolers on the instruments, (iii) reduce spatial temperature gradients in cryogenic components, and (iv) afford long continuous service life of the telescope. Passive two-phase capillary cooling technologies such as heat pipes, Loop Heat Pipes (LHPs), and Capillary pumped Loops (CPLs) have proven themselves capable of performing necessary thermal control functions for room temperature applications. They have no mechanical moving part to wear out or to introduce unwanted vibration to the instruments and, hence, are reliable and maintenancefree. However, utilizing these capillary devices for cryogenic cooling still remains a challenge because of difficulties involving the system start-up and operation in a warm environment. An advanced concept of LHP using Hydrogen as the working fluid was recently developed to demonstrate the cryocooling transport capabilities in the temperature range of 20-30K. A full-size demonstration test loop − appropriately called H2-ALHP_2 − was constructed and performance tested extensively in a thermal vacuum chamber. It was designed specifically to manage "heat parasitics" from a warm surrounding, enabling it to start up from an initially supercritical state and operate without requiring a rigid heat shield. Like room temperature LHPs, the H2-ALHP transport lines were made of small-diameter stainless steel tubing that are flexible enough to isolate the cryocooler-induced vibration from the IR instruments. In addition, focus of the H2-ALHP research and development effort was also placed on the system weight saving for space-based applications.

Lockheed Martin's Advanced Technology Center (LM-ATC) has delivered a flight model cryocooler system for NASA's Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS). This system was developed as a New Millennium Program to demonstrate technologies, which enable revolutionary science. One of the new technologies for future generation remote sensors is the two-stage pulse tube cryocooler. This cooler is presently being integrated with the spectrometer at Space Dynamics Laboratory (SDL) in preparation for system tests. In addition, a similar two-stage Engineering Model cryocooler was developed for a different program. LM-ATC's pulse tube cryocoolers employ a unique staging arrangement, resulting in high power efficiency, compact and efficient packaging, and interfacing and excellent reliability. They are robust and simple, consisting of a two-stage coldhead with no moving parts, driven by a moving magnet compressor and powered by a high-efficiency electronic controller that includes ripple suppression and vibration cancellation. The design is a "split" system in which the compressor and cold head are separated by a transfer line. The approach allows on orbit adjustment of the relative cooling loads and temperatures of the two stages. These two stage cryocoolers are developed for simultaneous cooling of the focal plane and the optics at two different temperatures. The electronic controller provides precise temperature control of the focal plane and also provides a vibration reduction loop. The total mass of these systems, including electronics, is approximately 9 Kg. This paper presents the performance and characteristics of these systems.

The Northrup Grumman Space Technologies High Efficiency Cryocooler (NGST HEC) was designed to support a 10 Watt cooling load at 95 Kelvin while rejecting heat to an effective sink interface temperature of 300 Kelvin. This design is an example of the pulse tube with inertance tube variant of the Stirling thermodynamic cycle whose compressor section uses dual opposed pistons to minimize vibration imparted to any cooling load through the cold end. The Air Force Research Laboratory has characterized the extended performance envelope of this refrigeration system, including its off nominal design point performance and efficiency, its response to transient loading and rejection temperatures, and its cool down performance from ambient. In order to assess this system's long term ability to support extended continuous duty space missions, this cryocooler has been running continuously for over two years, as part of a five year study on whether significant degradation in performance can be measured over that time. Finally, comparison of this cryocooler to other similar space qualifiable refrigeration systems has been made.

The Wide-Field Infrared Survey Explorer (WISE) is a MIDEX mission that is being developed by the Jet Propulsion Laboratory (JPL) to address several of NASA's Astronomical Search of Origins (ASO) objectives. The WISE instrument, developed by the Space Dynamics Laboratory (SDL), includes a cryogenically cooled telescope (at < 13K) and four focal plane assemblies (2 at 7.6K, 2 at 32K). Cooling of the instrument is accomplished by a dual-stage solid hydrogen cryostat that is developed by the Lockheed Martin Advanced Technology Center (LM-ATC). This paper provides a combined overview of the WISE cryostat design and thermal support system.

TNO, in cooperation with Micromega-Dynamics, SRON, Dutch Space and CSL, has developed a compact breadboard cryogenic Optical Delay Line for use in future space interferometry missions. The work is performed under ESA contract in preparation for the DARWIN mission. The breadboard delay line is representative of a future flight mechanism, with all used materials and processes being flight representative. The delay line has a single stage voice coil actuator for Optical Path Difference (OPD) control, driving a two-mirror cat's eye. Magnetic bearings are used for guiding. They provide frictionless and wear free operation with zero-hysteresis. The manufacturing, assembly and acceptance testing have been completed and are reported in this paper. The verification program, including functional testing at 40 K, will start in the final quarter of 2005.

The ASTRO-F is an on-going infrared satellite mission covering 2-200 μm infrared wavelengths. Not only the all-sky survey in the mid-IR and far-IR, but also deep pointing observations are planned especially at 2-26 μm. In this paper, we focus on the near-infrared (NIR) channel of the infrared camera (IRC) on board ASTRO-F, and describe its design, and results of the imaging mode performance evaluation as a single component. The NIR consists of 4 lenses (Silicon - Silicon - Germanium - Silicon) with a 412 * 512 In:Sb detector. Three broad-band filters, and two spectroscopic elements are installed covering 2-5 μm wavelengths. Since the ASTRO-F telescope and the focal plane are cooled to 6 K, the evaluation of adjustment of the focus and the end-to-end test of the whole NIR camera assembly have to be done at cryogenic temperature. As a result of measurements, we found that the transverse magnification and distortion are well matched with the specification value (1 versus 1.017 and 1 %), while the chromatic aberration, point spread function, and encircled energy are slightly degraded from the specification (300 μm from 88 μm, > 1pixel from ~ 1pixel, 80 % encircled energy radius > 1pixel from ~ 1pixel). However, with these three measured values, in-flight simulations show the same quality as specification without degradation. In addition to the image quality, we also verified the ghost image generated from the optical element (1 % energy fraction to the original image) and the slightly narrowed field of view (10' * 9.5' from 10' * 10'). For the responsivity, the NIR shows expected response. Totally, the NIR imaging mode shows satisfactory results for the expected in-flight performance.