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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
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NASA NTRS1979

A small helium-cooled infrared telescope for Spacelab 2

A helium cooled telescope of 15 cm aperture is being designed and constructed jointly by the University of Arizona, the Smithsonian Astrophysical Observatory and the Marshall Space Flight Center for high sensitivity infrared astronomical observations from Spacelab 2. A focal plane array of ten detectors provide a total field of view of 3 deg and cover the wavelength regions 4.5-8.5, 6-7, 9-16, 18-30 and 80-120 microns. A highly redundant all sky survey will be conducted by repeated scanning of the sky during many orbits of the spacecraft. High redundancy will allow discrimination among variable and constant celestial sources and several types of variable nearby sources. The principal astronomical result of the survey will be the absolute flux measurement of low surface brightness, large scale celestial infrared emissions but it will also extend existing IR sky surveys by a factor of 10 in point source sensitivity. The experiment will also make significant engineering measurements of contaminants in the Shuttle environment, test the technology of storage and utilization of large quantities of superfluid helium in space and test mechanical designs for future infrared telescopes for the Space Shuttle.

Gautier, T. N., III↗
NASA NTRS1981

Test results of Spacelab 2 infrared telescope focal plane

The small helium cooled infrared telescope for Spacelab 2 is designed for sensitive mapping of extended, low-surface-brightness celestial sources as well as highly sensitive investigations of the shuttle contamination environment (FPA) for this mission is described as well as the design for a thermally isolated, self-heated J-FET transimpedance amplifier. This amplifier is Johnson noise limited for feedback resistances from less than 10 to the 8th power Omega to greater than 2 x 10 to the 10th power Omega at T = 4.2K. Work on the focal plane array is complete. Performance testing for qualification of the flight hardware is discussed, and results are presented. All infrared data channels are measured to be background limited by the expected level of zodiacal emission.

Young, E. T.↗
NASA NTRS1984

Lightning mapper development: Status and requirements

The feasibility for the detection and location of lightning on a continuous basis using a sensor in geostationary orbit was established. Measurements of the optical characteristics of lightning and the capabilities of solid state mosaic focal plane arrays, indicate that the question is how high a detection efficiency can be achieved. The lightning mapper development to strengthen the scientific justification for placing a lightning sensor in geostationary orbit is discussed. The U-2 and ground based lightning research, modeling, and theoretical studies are reported.

Christian, H. J.↗
NASA NTRS1984

Cryogenic telescope on the Infrared Astronomical Satellite (IRAS)

The Infrared Astronomical Satellite (IRAS) has completed an unbiased all-sky survey at wavelengths from 10 to 100 microns. The design and performance of the focal plane array is described with emphasis on in-orbit measurements of the sensitivity and stability. In the four broad spectral bands centered at 12, 25, 60, and 100 microns, the system noise equivalent flux density (NEFD) values are in Jy/(Square root of Hz), 0.03, 0.025, 0.046, and 0.21, respectively (Jansky = 10 to the -26th W/sq m/Hz). For point sources, a single scan at the survey rate of 3.8 arcmin/s yields limiting flux densities at the 3-sigma confidence level of 0.36, 0.30, 0.39, and 1.2 Jy. The dc stability of the junction field effect transistor (JFET) amplifiers and the excellent off-axis rejection of the telescope permit total flux measurements of extended infrared emission at levels below 6,000,000 Jy/sr. Response of the extrinsic silicon and germanium photo-detectors to ionizing radiation is described.

Low, F. J.↗
NASA NTRS1983

High-density Schottky barrier IRCCD sensors for remote sensing applications

It is pointed out that the ambitious goals envisaged for the next generation of space-borne sensors challenge the state-of-the-art in solid-state imaging technology. Studies are being conducted with the aim to provide focal plane array technology suitable for use in future Multispectral Linear Array (MLA) earth resource instruments. An important new technology for IR-image sensors involves the use of monolithic Schottky barrier infrared charge-coupled device arrays. This technology is suitable for earth sensing applications in which moderate quantum efficiency and intermediate operating temperatures are required. This IR sensor can be fabricated by using standard integrated circuit (IC) processing techniques, and it is possible to employ commercial IC grade silicon. For this reason, it is feasible to construct Schottky barrier area and line arrays with large numbers of elements and high-density designs. A Pd2Si Schottky barrier sensor for multispectral imaging in the 1 to 3.5 micron band is under development.

Elabd, H.↗
NASA NTRS1984

Infrared and visible detector electronics for the Infrared Astronomical Satellite (IRAS)

The paper describes the detectors, preamplifiers, and processing electronics; the system characterization test methods and results; and the performance of the detectors and electronics during the first month of on-orbit operation of the IRAS telescope. The Focal Plane Array (FPA) consists of 62 IR channels and 8 visible channels operating at 2.5 K. The IR detectors are grouped in eight 7 or 8 channel staggered linear subarrays with shared bias voltage; the visible detectors are grouped in two 4 channel skewed arrays, also with shared bias. Each channel detector is dc coupled to a TIA preamplifier through a very low power thermally isolated JFET source follower operating at about 65 K within the FPA housing. The visible channel detectors are ac coupled to TIA preamplifiers and signal chain electronics using MOSFET source followers operating at about 2.5 K within the FPA housing. The detectors, preamplifiers, analog electronics, and grounding are discussed as they evolved and were implemented during FPA retrofit, telescope integration, and preparation for launch.

Langford, D. L.↗
NASA NTRS1983

A Shuttle Imaging Spectrometer Experiment for the late 1980's

The Shuttle Imaging Spectrometer Experiment (SISEX), proposed as a next experimental step in the development of advanced earth remote sensing technology, is capable of imaging the earth's surface simultaneously in 128 spectral bands covering the range from 0.4 to 2.5 micrometers. Laboratory and field measurements have suggested the utility of high-spectral-resolution remote sensing, and an aircraft-borne precursor to the SISEX has demonstrated the ability to distinguish among differing vegetation and rock types - in certain cases making unique identifications. The SISEX instrument utilizes an area-array focal plane, populated by visual- and infrared-sensitive detectors, to acquire simultaneous spatial and spectral information on a line-by-line basis. The spectrum is dispersed by means of a prism spectrometer. The performance analysis indicates that the scientific requirements for radiometric precision can be achieved using optics with an effective circular aperture of 11 cm.

Wellman, J. B.↗
NASA NTRS1987

Growing Single Crystals of Compound Semiconductors

Defect reduced by preventing melt/furnace contact and suppressing convention. Large crystals of compound semiconductors with few defects grown by proposed new method. Such materials as gallium arsenide and cadmium telluride produced, with quality suitable for very-large-scale integrated circuits or for large focal-plane arrays of photodetectors. Method used on small scale in Earth gravity, but needs microgravity to provide crystals large enough for industrial use.

Naumann, Robert J.↗
NASA NTRS1986

Recent developments in materials and detectors for the infrared; Proceedings of the Meeting, Cannes, France, November 25, 26, 1985

The present conference on advancements in IR-sensitive materials and detector technologies employing them gives attention to thermal detectors, focal plane array processing detectors, novel detector designs, general properties of IR optics materials, and preparation methods for such materials. Specific topics encompass the fabrication of InSb MIS structures prepared by photochemical vapor deposition, IR heterodyne detectors employing cadmium mercury telluride, low microphony pyroelectric arrays, IR detection based on minority carrier extrusion, longwave reststrahl in IR crystals, and molecular beam techniques for optical thin film fabrication.

Morten, F. D.↗
NASA NTRS1987

Imaging spectrometers for terrestrial and planetary remote sensing - A progress report

Attention is given to two major design approaches, the 'whiskbroom' and the 'pushbroom', in the present consideration of imaging spectroscopy for both planetary and terrestrial missions. A near-IR mapping spectrometer has been developed for the Galileo Jupiter Orbiter Mission; on the basis of this design, and incorporating focal plane array technology improvements, a family of imaging spectrometers exemplified by the Visual and IR Mapping Spectrometer is under development for other planetary missions.

Wellman, John B.↗
NASA NTRS1989

Composite Semiconductor Substrates

Epitaxial structure of three semiconductor materials - silicon, gallium arsenide, and cadmium telluride - makes possible integrated monolithic focal-plane arrays of photodectors. Silicon layer contains charge-coupled devices, gallium arsenide layer contains other fast electronic circuitry, and cadmium telluride layer serves as base for array of mercury cadmium telluride infrared sensors. Technique effectively combines two well-established techniques; metalorganic chemical-vapor deposition (MOCVD) and molecular-beam epitaxy (MBE). Multilayer structure includes HgCdTe light sensors with Si readout devices and GaAs signal-processing circuits. CdTe layer provides base for building up HgCdTe layer.

Nouhi, Akbar↗
NASA NTRS1988

Compact imaging spectrometer for induced emissions

On the basis of spectral measurements made from the Space Shuttle and on models of the possible Space Station external environment, it appears likely that, even at the planned altitudes of Space Station, photon emissions will be induced. These emissions will occur to some degree throughout the ultraviolet-visible-infrared spectrum. The emissions arise from a combination of processes including gas phase collisions between relatively energetic ambient and surface emitted or re-emitted atoms or molecules, where the surface raises some species to excited energy states. At the present time it is not possible to model these processes or the anticipated intensity levels with any accuracy, as a number of fundamental parameters needed for such calculations are still poorly known or unknown. However, it is possible that certain spectral line and band features will exceed the desired goal that concomitant emissions not exceed the natural zodiacal background. Also, in the near infrared and infrared, it appears that this level will be exceeded to a significant degree. Therefore it will be necessary to monitor emission levels in the vicinity of Space Station, both in order to establish the levels and to better model the environment. A small spectrometer is briefly described which is suitable for monitoring the spectrum from 1200 A to less than or equal to 12,000 A. The instrument uses focal plane array detectors to image this full spectral range simultaneously. The spectral resolution is 4 to 12 A, depending on the portion of the wavelength range.

Torr, Douglas G.↗
NASA NTRS1988

A compact imaging spectrometer for studies of space vehicle induced environment emissions

On the basis of spectral measurements made from the Space Shuttle and on models of the possible Space Station external environment, it appears likely that, even at the planned altitudes of Space Station, photon emissions will be induced. These emissions will occur to some degree throughout the UV-visible-IR spectrum. The emissions arise from a combination of processes including gas phase collisions between relatively energetic ambient and surface emitted or re-emitted atoms or molecules, where the surface raises some species to excited energy states. At present it is not possible to model these processes or the anticipated intensity levels with accuracy, as a number of fundamental parameters needed for such calculations are still poorly known or unknown. However, it is possible that certain spectral line and band features will exceed the desired goal that contaminant emissions not exceed the natural zodiacal background. However, in the near infrared and infrared, it appears that this level will be exceeded to a significant degree. Therefore it will be necessary to monitor emission levels in the vicinity of Space Station, both in order to establish the levels and to better model the environment. In this note, we briefly describe a small spectrometer that is suitable for monitoring the spectrum from 1200A to less than or approximately 12,000A. This instrument uses focal plane array detectors to image this full spectral range simultaneously. The spectral resolution is 4 to 12A, depending on the portion of the wavelength range.

Torr, Marsha R.↗
NASA NTRS1988

A Near-Infrared Mapping Spectrometer for investigation of Jupiter and its satellites

The Near-Infrared-Mapping Spectrometer (NIMS) is one of the science instruments in the Galileo mission, which will explore Jupiter and its satellites in the mid-1990's. The NIMS experiment will map geological units on the surfaces of the Jovian satellites and characterize their mineral content; and, for the atmosphere of Jupiter, investigate cloud properties and the spatial and temporal variability of molecular abundances. The optics are gold-coated reflective and consist of a telescope and a grating spectrometer. The balance of the instrument includes a 17-detector (silicon and indium antimonide) focal plane array, a tuning fork chopper, microprocessor-controlled electronics, and a passive radiative cooler. A wobbling secondary mirror in the telescope provides 20 pixels in one dimension of spatial scanning in a pushbroom mode with 0.5 mr x 0.5 mr instantaneous field of view. The spectral range is 0.7-5.2 microns; resolution is 0.025 micron. NIMS is the first infrared experiment to combine both spatial and spectral mapping capability in one instrument.

Aptaker, Irving M.↗
NASA NTRS1988

Feasibility of an uncooled imaging spectrometer for the exploration of the solar system

A state-of-the-art imaging spectrometer concept is presented for visible-midwavelength IR spectral region studies of the solar system that obviates the until-now essential use of cryogenic cooling. This uncooled imaging spectrometer configuration is evaluated in view of the prospective environments of the instrument in various spacecraft orbits, as well as in light of various available photodetector materials and sensor focal plane array configurations.

Liaw, H. M.↗
NASA NTRS1989

The tapered slot antenna - A new integrated element for millimeter-wave applications

Tapered slot antennas (TSAs) with a number of potential applications as single elements and focal-plane arrays are discussed. TSAs are fabricated with photolithographic techniques and integrated in either hybrid or MMIC circuits with receiver or transmitter components. They offer considerably narrower beams than other integrated antenna elements and have high aperture efficiency and packing density as array elements. Both the circuit and radiation properties of TSAs are reviewed. Topics covered include: antenna beamwidth, directivity, and gain of single-element TSAs; their beam shape and the effect of different taper shapes; and the input impedance and the effects of using thick dielectrics. These characteristics are also given for TSA arrays, as are the circuit properties of the array elements. Different array structures and their applications are also described.

Yngvesson, K. Sigfrid↗
NASA NTRS1990

Ge/Si Integrated Circuit For Infrared Imaging

Proposed integrated circuit consists of focal-plane array of metal/germanium Schottky-barrier photodetectors on same chip with silicon-based circuits that processes signals from photodetectors. Made compatible with underlying silicon-based circuitry by growing germanium epitaxially on silicon circuit wafers. Metal deposited in ultrahigh vacuum immediately after growth of germanium. Combination of described techniques results in high-resolution infrared-imaging circuits of superior performance.

Fathauer, Robert W.↗
NASA NTRS1990

Layered Internal-Photoemission Sensor

High quantum efficiency achieved without multiple layer contacts. Proposed infrared sensor based on photoemission from multiple layers of metal silicide sandwiched between layers of silicon. Suitable for use in focal-plane arrays. Layered internal-photoemission sensor has positive/intrinsic/negative structure modified by inclusion of layers or islands of metal silicide. Holes photo-excited from silicide regions and swept to detection by reverse-bias electric field in intrinsic silicon. Easier to make because internal layers allowed to "float" electrically, contact being made with only two outer semiconductor layers.

Fathauer, Robert W.↗