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NASA NTRS1976

A CCD scanned (Hg, Cd)Te array for earth viewing applications

A 9 channel demonstration of 10 micrometer photoconductive mercury cadmium telluride detector array, bipolar preamplifiers, and a Si CCD multiplexer, integrated into a focal plane assembly and operating at 105 K and at 17 Hz is reported. The result of a direct coupling experiment between a 5-micrometer photovoltaic mercury cadmium telluride photodiode and a CCD is revealed. No appreciable degradation in the signal-to-noise ratio was experienced.

Iwasa, S.↗

NASA NTRS1979

Spacelab 2 infrared telescope cryogenic system

The paper discusses the development of a cryogenic helium system to provide cooling to a scanning infrared telescope for the Spacelab 2 mission. The infrared optical/detector system and related electronics are being developed by the Smithsonian Astrophysical Observatory and the University of Arizona. A superfluid helium dewar and porous plug phase separator permit gas cooling of the infrared focal plane assembly to about 2.5 K, and of the two telescope sections to 8 K and 60 K. The design of the cryogenic system,including a commandable vacuum cover, and the prelaunch liquid helium servicing and maintenance approach were discussed. It is concluded that the system will satisfy the Infrared Telescope requirements, and the superfluid helium system shall be capable of satisfying cryogenic helium cooled requirements for the next several years.

Urban, E. W.↗

NASA NTRS1980

Thermal IR imaging system using a self-scanned HgCdTe/CCD detector array

It is likely that future high resolution earth observation imaging systems will utilize self-scanned IR detectors. In an initial step toward this goal, an IR imaging system operating in the 10 to 12 micron spectral region has been developed. This system uses a 9-element HgCdTe/CCD linear array operating in the photoconductive mode, nine pre-amplifiers and a silicon CCD multiplexer integrated into a focal plane assembly. Opto-mechanical techniques are used to scan the scene and images are produced in real time. The imaging performance of this system is described and measurements of noise, responsivity, specific detectivity, and detector sensitivity profiles are presented. The requirements for more advanced detector arrays for use in future NASA remote sensing missions are also discussed.

Husain-Abidi, A. S.↗

NASA NTRS1982

Thematic mapper flight model preshipment review data package. Volume 2, part B: Subsystem data

Summarized performance data are presented for the following major subsystems of the thematic mapper: the focal plane assembly, the radiative cooler, the radiative cooler door assembly, the top optical assembly, and the telescope assembly. Reference lists of the configurations status and of nonconforming material reports, failure reports, and requests for deviation/waiver are included.

Source record↗

NASA NTRS1984

The Infrared Astronomical Satellite (IRAS) mission

The Infrared Astronomical Satellite (IRAS) consists of a spacecraft and a liquid helium cryostat that contains a cooled IR telescope. The telescope's focal plane assembly is cooled to less than 3 K, and contains 62 IR detectors in the survey array which are arranged so that every source crossing the field of view can be seen by at least two detectors in each of four wavelength bands. The satellite was launched into a 900 km-altitude near-polar orbit, and its cryogenic helium supply was exhausted on November 22, 1983. By mission's end, 72 percent of the sky had been observed with three or more hours-confirming scans, and 95 percent with two or more hours-confirming scans. About 2000 stars detected at 12 and 25 microns early in the mission, and identified in the SAO (1966) catalog, have a positional uncertainty ellipse whose axes are 45 x 9 arcsec for an hours-confirmed source.

Neugebauer, G.↗

NASA NTRS1984

The Advanced X-ray Astrophysics Facility instrument interface requirements

A variety of instruments will be placed at the focus of the Advanced X-ray Astrophysics Facility (AXAF) telescope, either by moving them into focus through the use of an instrument carousel or by moving the telescope assembly. Focal plane instrument categories under consideration for AXAF encompass high and moderate resolution X-ray cameras, X-ray spectrometers, and polarimeters; some of these instruments may require such consumables as a cryogen, in the case of solid state device cooling, or a gas, as in the case of proportional counters. Attention is presently given to interface requirements impacting on the maintenance that must be conducted over the 15-year service life of AXAF, and, especially, on the 'aspect solution' criteria that must be met to minimize stiffness stability criteria.

Weisskopf, M. C.↗

NASA NTRS1989

The soft x ray telescope for Solar-A

The Solar-A satellite being prepared by the Institute for Sapce and Astronautical Sciences (ISAS) in Japan is dedicated to high energy observations of solar flares. The Soft X Ray Telescope (SXT) is being prepared to provide filtered images in the 2 to 60 A interval. The flight model is now undergoing tests in the 1000 foot tunnel at MSFC. Launch will be in September 1991. Earlier resolution and efficiency tests on the grazing incidence mirror have established its performance in soft x rays. The one-piece, two mirror grazing incidence telescope is supported in a strain free mount separated from the focal plane assembly by a carbon-epoxy metering tube whose windings and filler are chosen to minimize thermal and hygroscopic effects. The CCD detector images both the x ray and the concentric visible light aspect telescope. Optical filters provide images at 4308 and 4700 A. The SXT will be capable of producing over 8000 of the smallest partial frame images per day, or fewer but larger images, up to 1024 x 1024 pixel images. Image sequence with two or more of the five x ray analysis filters, with automatic exposure compensation to optimize the charge collection by the CCD detector, will be used to provide plasma diagnostics. Calculations using a differential emission measure code were used to optimize filter selection over the range of emission measure variations and to avoid redundancy, but the filters were chosen primarily to give ratios that are monotonic in plasma temperature.

Brown, W. A.↗

NASA NTRS1990

Exploring the Universe with the Hubble Space Telescope

A general overview is given of the operations, engineering challenges, and components of the Hubble Space Telescope. Deployment, checkout and servicing in space are discussed. The optical telescope assembly, focal plane scientific instruments, wide field/planetary camera, faint object spectrograph, faint object camera, Goddard high resolution spectrograph, high speed photometer, fine guidance sensors, second generation technology, and support systems and services are reviewed.

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NASA NTRS1993

Pointing and figure control system for a space-based far-IR segmented telescope

A pointing and figure control system for two space-based far-IR telescopes, the 10-20 m Large Deployable Reflector and the 3.6 m Submillimeter Intermediate Mission, is described. The figure maintenance control system is designed to counter the optical elements translational and rotational changes induced by long-term thermal drifts that the support structure may experience. The pointing system applies optical truss to telescope pointing; a laser metrology system is used to transfer pointing informaton from an external fine guidance sensor to the telescope optical boresight, defined by the primary mirror, secondary mirror, and focal plane assembly.

Lau, Kenneth↗

NASA NTRS1991

Infrared focal plane design for the Comet Rendezvous/Asteroid Flyby and Cassini Visible and Infrared Mapping Spectrometers

A focal plane assembly combining hybrid electronic components with passive optical components within a single hermetically sealed package has been designed by Cincinnati Electronics to meet the performance requirements imposed by the Comet Rendezvous/Asteroid Flyby (CRAF) and Cassini Visible and Infrared Mapping Spectrometers (VIMSs). A single line array of 256 InSb photodiodes, accessed by two 1 x 128 multiplexers, provides continuous spectral coverage from 0.85 to 5.1 microns. Intrinsic field-of-view apertures and a unique order sorting filter require critical optical alignment within the hybrid. FPA performance requirements, design approach, and critical issues are discussed.

Staller, Craig↗

NASA NTRS1995

Development of 3-Phase CCD Timing Generator

Charge-Coupled Devices (CCDs) are used in a wide range of commercial, scientific, and defense applications. They are primarily utilized for imaging and spectroscopic functions. Compact, cost-effective technology to miniaturize the auxiliary electronics required to operate the CCD is highly desirable. Because of the importance of reducing size and weight in defense and space applications, emphasis must be placed on the reduction in size. The purpose of this project is to minimize the CCD timing generator electronics for 3-phase CCDs by replacing conventional ICs with a single programmable IC. This timing generator will give the user the ability to vary the number of horizontal and vertical pixels and to choose between integration and readout modes. This, in turn, will reduce the size and weight of CCD focal plane assemblies as a whole.

Bennett, Kory L.↗

NASA NTRS2000

Photogrammetry of the Map Instrument in a Cryogenic Vacuum Environment

MAP Instrument requirements dictated that the instruments Focal Plane Assembly (FPA) and Thermal Reflector System (TRS) maintain a high degree of structural integrity at operational temperatures (< 50K). To verify integrity at these extremes, an elaborate test fixture was constructed to provide a large cryogenic (< 20K) radiative environment and a mobile photogrammetry camera. This paper will discuss MAP's Instrument requirements, how those requirements were verified using photogrammetry, and the test setup used to provide the environment and camera movement needed to verify the instrument's requirements.

Hill, M.↗

NASA NTRS2006

Results and Lessons from MODIS Thermal Emissive Bands Calibration: Pre-launch to On-orbit

MODIS is a major instrument for the NASA EOS Terra (launched in December 1999) and Aqua (launched in May 2002) missions. It was designed and built to enhance and extend its heritage sensors' measurements and data records with applications covering a wide range of studies of the Earth's land, oceans, and atmosphere. Its 16 thermal emissive bands (TEB), each with 10 detectors, are located on the two cold focal plane assemblies (FPAs) controlled by a passive radiative cooler. Because of instrument design complexity and stringent calibration requirements, extensive calibration and characterization activities were conducted pre-launch by the sensor vendor for both Terra and Aqua MODIS. For TEB, these activities include characterization of detectors' noise and non-linearity and evaluation of their radiometric performance in thermal vacuum at difference instrument temperatures and FPA temperatures. In addition TEB system level response versus scan-angle (RVS) and relative spectral response (RSR) were characterized. MODIS TEB radiometric calibration transfer from pre-launch to on-orbit was performed using spectral bands' responses to the instrument on-board blackbody and a laboratory blackbody calibration source (BCS) traceable to NIST standards. This paper provides a summary of MODIS TEB pre-launch and on-orbit calibration and characterization activities, challenges, data analysis results, and lessons learned with focus on sensors' radiometric performance. A comparison between Terra and Aqua MODIS TEB performance is also presented. A similar summary for the reflective solar bands (RSB) is reported in a separate paper in these proceedings.

Xiong, X.↗

NASA NTRS2006

Results and Lessons from MODIS Reflective Solar Bands Calibration: Pre-launch to On-orbit

MODIS is a major instrument for the NASA EOS Terra (1aunched in December 1999) and Aqua (launched in May 2002) missions. It was designed and built to enhance and extend its heritage sensors' measurements and data records with applications covering a wide range of studies of the Earth's land, oceans, and atmosphere. MODIS has 36 spectral bands (0.41 - 14.4 micrometers) located on four focal plane assemblies (FPAs). It makes measurements at three nadir spatial resolutions: 250m (bands 1-2), 500m (bands 3-7), and lkm (bands 8-36). Because of instrument design complexity and stringent calibration requirements, extensive calibration and characterization activities were conducted pre-launch by the sensor vendor (Raytheon / Santa Barbara Remote Sensing) for both Tesa and Aqua MODIS. For the 20 reflective solar bands (RSB), these activities include measurements for the detectors noise characterization and radiometric performance, system level response versus scan-angle (RVS), polarization sensitivity, and relative spectral response (RSR). Key radiometric performance was evaluated using thermal vacuum observations. On-orbit MODIS RSB calibration is performed using a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system. The SD bi-directional reflectance factor (BRF) was characterized pre-launch by the sensor vendor with reference samples traceable to NIST reflectance standards. This paper provides a summary of Terra and Aqua MODIS RSB pre-launch and on-orbit calibration and characterization activities and results with focus on the detectors' noise characterization and radiometric performance. Challenging and concerning issues and lessons learned from RSB pre-launch calibration and their impact on post launch performance are also presented. A similar summary for MODIS thermal emissive bands (TEB) is reported in a separate paper in these proceedings.

Xiong, X.↗

NASA NTRS2007

Detector Noise Characterization and Performance of MODIS Thermal Emissive Bands

MODIS has 16 thermal emissive bands, a total of 160 individual detectors (10 for each spectral bands), located on the two cold focal plane assemblies (CFPA). MODIS TEB detectors were fully characterized pre-launch in a thermal vacuum (TV) environment using a NIST traceable blackbody calibration source (BCS) with temperatures ranging from 170 to 340K. On-orbit the TEB detectors are calibrated using an on-board blackbody (BB) on a scan-by-scan basis. For nominal on-orbit operation, the on-board BB temperature is typically controlled at 285K for Aqua MODIS and 290K for Terra MODIS. For the MODIS TEB calibration, each detector's noise equivalent temperature difference (NEdT) is often used to assess its performance and this parameter is a major contributor to the calibration uncertainty. Because of its impact on sensor calibration and data product quality, each MODIS TEB detector's NEdT is monitored on a daily basis at a fixed BB temperature and completely characterized on a regular basis at a number of BB temperatures. In this paper, we describe MODIS on-orbit TEB NEdT characterization activities, approaches, and results. We compare both pre-launch and on-orbit performance with sensor design specification and examine detector noise characterization impact on the calibration uncertainty. To date, 135 TEB detectors (out of a total of 160 detectors) in Terra MODIS (launched in December 1999) and 158 in Aqua MODIS (launched in May 2002) continue to perform with their NEdT below (or better than) their design specifications. A complete summary of all TEB noisy detectors, identified both pre-launch and on-orbit, is provided.

Xiong, X.↗

NASA NTRS2009

Formation Flying of Components of a Large Space Telescope

A conceptual space telescope having an aperture tens of meters wide and a focal length of hundreds of meters would be implemented as a group of six separate optical modules flying in formation: a primary-membrane-mirror module, a relay-mirror module, a focal-plane-assembly module containing a fast steering mirror and secondary and tertiary optics, a primary-mirror-figure-sensing module, a scanning-electron-beam module for controlling the shape of the primary mirror, and a sunshade module. Formation flying would make it unnecessary to maintain the required precise alignments among the modules by means of an impractically massive rigid structure. Instead, a control system operating in conjunction with a metrology system comprising optical and radio subsystems would control the firing of small thrusters on the separate modules to maintain the formation, thereby acting as a virtual rigid structure. The control system would utilize a combination of centralized- and decentralized-control methods according to a leader-follower approach. The feasibility of the concept was demonstrated in computational simulations that showed that relative positions could be maintained to within a fraction of a millimeter and orientations to within several microradians.

Mettler, Edward↗

NASA NTRS2010

IXO/XMS Detector Trade-Off Study

This document presents the outcome of the detector trade-off for the XMS instrument on IXO. This trade-off is part of the Cryogenic instrument Phase-A study as proposed to ESA in the Declaration of Interest SRONXMS-PL-2009-003 dated June 6, 2009. The detector consists of two components: a core array for the highest spectral resolution and an outer array to increase the field of view substantially with modest increase in the number of read-out channels. Degraded resolution of the outer array in comparison with the core array is accepted in order to make this scheme possible. The two detector components may be a single unit or separate units. These arrays comprise pixels and the components that allow them to be arrayed. Each pixel comprises a thermometer, an absorber, and the thermal links between them and to the rest of the array. These links may be interfaces or distinct components. The array infrastructure comprises the mechanical structure of the array, the arrangement of the leads, and features added to improve the integrated thermal properties of the array in the focal-plane assembly.

Kilbourne, Caroline Anne↗

NASA NTRS2011

The Detector Subsystem for the SXS Instrument on the Astro-H Observatory

The Soft X-ray Spectrometer (SXS) instrument on the Astro-H observatory is based on a 36 pixel x-ray calorimeter array cooled to 50 mK in a sophisticated spaceflight cryostat. The SXS is a true spatial-spectral instrument, where each spatially discrete pixel functions as a high-resolution spectrometer. Here we discuss the SXS detector subsystem that includes the detector array, the anticoincidence detector, the first stage amplifiers, the thermal and mechanical staging of the detector, and the cryogenic bias electronics. The design of the SXS detector subsystem has significant heritage from the Suzaku/XRS instrument but has some important modifications that increase performance margins and simplify the focal plane assembly. Notable improvements include x-ray absorbers with significantly lower heat capacity, improved load resistors, improved thermometry, and a decreased sensitivity to thermal radiation. These modifications have yielded an energy resolution of 3.5-4.0 eV FWHM at 6 keV for representative devices in the laboratory, giving considerable margin against the 7 eV instrument requirement. We expect similar performance in flight

Porter, Frederick↗