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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 289 records · Page 16
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NASA NTRS1979

Gallium-doped germanium, evaluation of photoconductors, part 1

Gallium-doped germanium far infrared detectors were evaluated at low temperatures and low background simulating the space environment. Signal and noise characteristics were determined for detector temperatures in the 2K to 4K range. Optimum performance occurs at about 2.5K for all devices tested. The minimum average NEP in the 40-130 micron region was found to be approximately 4 x 10 to the minus 17th power watt Hz(-1/2) at a frequency of 1 Hz.

Moore, W. J.↗
NASA NTRS1979

Degenerate dwarfs in future hard X-ray experiments

The hard X-ray characteristics of weak sources (dwarf novae and AM Her-like), and strong steady sources, are discussed. HEAO A2 light curves for the greater than 2 keV flux from SS Cygni are presented, along with the pulse height spectrum and inferred incident spectrum. With regard to the high luminosity degenerate dwarf candidates, it is noted that only for Sco X-1 and Cyg X-2 has even optical evidence for binary periodicity been seen. The attributes of suitable X-ray experiments are reviewed, concerning the simultaneous observation of low energy X-rays, a large area for studying short flares, low background, and the need for both broad band spectral response and high resolution.

Swank, J. H.↗
NASA NTRS1979

Infrared focal plane arrays for planetary missions

Requirements for infrared detector array focal planes suitable for a set of prospective planetary missions are developed. Using the Galileo mission to Jupiter as a starting point, objectives and constraints applicable to outer planet missions are developed. The concept for an advanced mapping spectrometer utilizing 128 x 128 element infrared detector arrays is described. Specific implementations for the Saturn Orbiter Dual Probe mission, a Mars Orbiter mission, and a Titan Orbiter mission are defined. The analysis indicates that within the 1 to 5 micron range, broad scientific objectives for these missions can be met using focal plane arrays with detectivities on the order of 10 to the 14th cm sq root of Hz per W. The realization of such high detectivities in a low background application will necessitate careful development of the method by which the detector signals are multiplexed and read out.

Wellman, J. B.↗
NASA NTRS1981

Measurement of HO2 and other trace gases in the stratosphere using a high resolution far infrared spectrometer at 28 Km

A progress report and data analyses from the December 1980 flight are presented. The following areas are covered: (1) computer analysis of the flight spectra to obtain phase corrected, normalized sums of spectra for retrieval of atmospheric profiles; (2) study of atmospheric HF, HCl, and H2O; (3) stratospheric H2O2 and HOCl; (4) laboratory spectroscopy of HOCl; and (5) design study of a new balloon gondola. The majority of the flight data were taken in the low background mode, i.e., one input to the spectrometer looking at the sky and the other looking at a LN2 temperature blackbody. An analysis of HF stratospheric measurements was undertaken in conjunction with the HF analysis. High quality spectra showing the HOCl q-branches under optically thin conditions were also obtained.

Traub, W. A.↗
NASA NTRS1982

Current NASA studies for a Far Ultraviolent Spectrographic Explorer (FUSE)

The NASA plans for FUSE, a satellite which obtains spectra with resolutions between 100,000 and 100 in the spectral regions from 912 to 1216A and 100 to 912A, are outlined. Scientific problems which can be tackled by FUSE, but not by IUE or the Space Telescope, are discussed. A grazing incidence echelle and a hybrid echelle design are presented. They have high throughput, large simultaneous spectral range, and low background photon counting statistics. The satellite operational organization is similar to that of IUE.

Linsky, J.↗
NASA NTRS1981

Infrared camera for 10-micron astronomy

An infrared imaging photometer employing a monolithic 32 x 32 pixel bismuth doped silicon charge injection device array is described. The device is primarily useful in the 8-13-micron atmospheric window. The detector is sufficiently sensitive to provide good performance on ground-based telescopes and promises to be very good for low background space flight operation.

Arens, J. F.↗
NASA NTRS1982

Sub-Kelvin temperatures in space

It is pointed out that the use of temperatures below 1 K in space would provide a significant improvement in several areas of research. The sensitivity of bolometers, for instance, can be improvead by as much as a factor of 50, if the operating temperature is lowered from 1.5 K to 0.3 K. A decrease in temperature to 0.1 K can provide even an improvement up to three orders of magnitude. Detectors based on the utilization of such improvements could be employed for far-infrared (100-1000 microns) photometry and spectroscopy in the low-background conditions of space. The study of critical phenomena in He-3/He-4 mixtures is also of interest, taking into account investigations at the tricritical point (0.87 K), which represents the junction of a first-order and a second-order transition. Tests in space are needed because gravity-related effects make adequate tests on earth impossible. He-3 refrigeration can be used to attain temperatures below 1 K. Adiabatic demagnetization can produuce temperatures below 0.3 K.

Kittel, P.↗
NASA NTRS1984

Astronomical application of IR CID technology

A portable microcomputer data system was developed to test a 2 x 64-element Si:Bi charge injection device (CID) infrared detector array on the Lick Observatory Shane telescope. An existing 0.5 m spectrograph was used for the tests after modification, and a spectral resolution of 1000 was achieved. Slow device response, due to the low background conditions in the spectrograph were shown. Astronomical data were later obtained, and a device read noise on the order of a few hundred electrons was achieved. The signal to noise ratios of the resulting spectra were about a factor of five lower than what could have been achieved with discrete photoconductive detectors. It is concluded that the CID array is competitive for applications in backgrounds lower than those used in the tests.

Rank, D. M.↗
NASA NTRS1984

A preliminary design study on an acoustic muffler for the laminar flow transition research apparatus

An acoustic muffler design of a research tool for studying laminar flow and the mechanisms of transition, the Laminar Flow and Transition Research Apparatus (LFTRA) is investigated. Since the presence of acoustic pressure fluctuations is known to affect transition, low background noise levels in the test section of the LFTRA are mandatory. The difficulties and tradeoffs of various muffler design concepts are discussed and the most promising candidates are emphasized.

Abrahamson, A. L.↗
NASA NTRS1985

Detection and Symbol Synchronization for Multiple-bit Per Photon Optical Communications

Methods of detection and synchronization in a highly efficient direct detection optical communication system are reported. Results of measurements on this moderate-rate demonstration system capable of transmitting 2.5 bits/detected photon in low-background situations indicate that symbol slot synchronization is not a problem, and that a simple symbol detection scheme is adequate for this situation. This system is a candidate for interplanetary optical communications.

Marshall, W. K.↗
NASA NTRS1984

IRAS observations of cometary dust

It is pointed out that solid material present in the coma and tail of a comet is revealed by the scattering of sunlight and thermal emission of absorbed solar radiation. The large beam size and low background of the cold Infrared Astronomy Satellite (IRAS) telescope make it extremely well suited to the measurement of faint diffuse thermal emission from solid grains associated with comets. The IRAS project was conducted jointly by the Netherlands, the United Kingdom, and the U.S. Its basic objective involved a survey of the sky in four wavelength regions centered on 12, 25, 60, and 100 microns. The present paper is mainly concerned with IRAS observations of the coma-nucleus regions as defined by the maximum in the intensity distribution. Attention is given to circumstances of comet observations, dust production rates, and a discussion of the results.

Walker, R. G.↗
NASA NTRS1986

The HXII gas system

Two gas proportional counters were designed: one detector was patterned after the HEAO-1 design which possesses a proven low background capability at atmospheric pressure, and the other was a parallel planar geometry detector with an extensive drift region. The actual performance of the detectors was evaluated with emphasis on background rejection efficiency and position resolution.

Source record↗
NASA NTRS1985

Experimental performance of a 1-kilowatt arcjet thruster

A formerly unused cathode and anode/nozzle assembly from a flight model arcjet was tested with nitrogen, hydrogen, and nitrogen-hydrogen mixture simulating ammonia decomposition products at arc power levels from about 300 to 950 W. Two different power sources and two nozzle configurations were tested at low background pressures to exclude facility effects. Increased nozzle expansion ratio improved cold flow nozzle efficiency from 0.8 to 0.9. Hydrogen thrust efficiency of 0.26 at 872 sec specific impulse matched some 1964 performance on a similar device. Simulated ammonia thrust efficiency was 0.31 at 422 sec. Spontaneously occurring voltage mode changes at constant arc current could be partially stabilized with appropriate power source characteristics. In the higher voltage mode specific impulse was higher, but thrust efficiency changed only slightly from that of the lower voltage mode. Sustained tests of up to 2 hr duration exhibited no apparent performance degradation with time.

Nakanishi, S.↗
NASA NTRS1986

Proceedings of the Second Infrared Detector Technology Workshop

The workshop focused on infrared detector, detector array, and cryogenic electronic technologies relevant to low-background space astronomy. Papers are organized into the following categories: discrete infrared detectors and readout electronics; advanced bolometers; intrinsic integrated infrared arrays; and extrinsic integrated infrared arrays. Status reports on the Space Infrared Telescope Facility (SIRTF) and Infrared Space Observatory (ISO) programs are also included.

Mccreight, C. R.↗
NASA NTRS1986

Dark current measurement in photoconductors

The Space Infrared Telescope Facility (SIRTF) is envisioned as a next generation space observatory for observations between 2 and 700 microns. In order to address many of the important scientific questions in areas such as cosmology, star formation, and galaxy evolution, infrared detectors of unparalleled sensitivity will be required. Dark current measurements are described for a number of different discrete photoconductive detectors that may be of importance at the very low backgrounds expected with SIRTF.

Young, E. T.↗
NASA NTRS1986

Development of 30 micrometers extrinsic silicon multiplexed infrared deterctor array

Two hybrid infrared (IR) detector arrays of antimony-doped silicon (Si:Sb) were produced and tested to evaluate their potential for use in low-background IR astronomy applications. The format of the arrays is 58 x 62 elements, with 76 micron-square pixels. A random-access, switched metal-oxide semiconductor field effect transistor (MOSFET) silicon multiplexer is used to read out the array elements. Reduced-background tests of signal, noise, and noise equivalent power were conducted over the temperature range 3.2 to 12 K. The arrays were found to have good sensitivity and good uniformity.

Orias, G.↗
NASA NTRS1988

Transition prediction in external flows via linear stability theory

Linear stability theory results are presented for flight and low-disturbance wind tunnels, at low and high speeds, and for T-S, Gortler, and cross-flow modes. Results show that, in the absence of Morkovin 'bypasses', transition at low background disturbance levels corresponds to N-factors of the order of 9 to 11, provided that phenomena such as curvature effects are included. The results point to a wider range of applicability for the e exp N method than previously conjectured, and suggest that the e exp N method can be used to parametrize transition predictions as a function of parameters which affect the mean flow profiles for such purposes as LFC and minimum drag design.

Bushnell, D. M.↗
NASA NTRS1988

An introduction to blocked impurity band detectors

Blocked impurity band detectors fabricated using standard silicon technologies offer the possibility of combining high sensitivity and high accuracy in a single detector operating in a low background environment. The solid state photomultiplier described by Petroff et al., which is a new type of blocked impurity band detector, offers even higher sensitivity as well as operation in the visible spectral region. The principle of operation and possible application of blocked impurity band detectors for stellar seismology and the search for extra-solar planets are described.

Geist, Jon↗