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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Remote sensing technology - The 24-channel multispectral scanner.

The multispectral scanner system installed in the NASA C-130 aircraft for use in the Earth Observations Aircraft Program constitutes a 24-channel imaging spectrometer that senses electromagnetic energy in the spectral interval from .34 to 13 microns. Energy reflected or emitted from the terrain and system calibration sources is collected by a scan mirror, reflected into collecting optics, and brought to a focus in a plane containing a 0.09 inch square aperture. A dichroic optical element splits the energy which passes through the aperture into two wavelength bands (wavelengths above and below 2 microns). These wavelength bands are then dispersed spectrally into 24 distinct spectral bands by two grating spectrometers. The spectral intervals are transformed into electrical signals by separate detector-preamplifier combinations, and the signals are used as inputs to a video processor in an airborne electronics console. System operation and performance are described.

Hayre, H. S.↗
NASA NTRS1973

Design and performance characteristics of the Vertical Temperature Profile Radiometer /VTPR/ for atmospheric temperature soundings.

Description of the design and operation of a radiometer which derives atmospheric temperature profiles on the basis of spectral measurements in eight optical filter channels. The radiometer achieves its eight-channel capability by sequentially viewing the eight optical filters mounted in a rotating filter wheel, with a single IR detector and electronic amplification channel processing the signal for all the filters. The advantages and disadvantages of this sequential approach as compared to eight 'parallel' radiometric channels are discussed. The proposed radiometer provides a relative calibration accuracy between seven out of the eight channels of better than 0.1% rms of the full dynamic range. The absolute accuracy achievable between in-flight calibrations of six minutes, or between two-hour calibrations using optical temperature correction factors, is better than an rms value of 0.15% of full scale. The radiometric correlation between the in-flight calibration source of the instrument and a reference standard blackbody is better than an rms value of 0.5% of full scale.

Falbel, G.↗
NASA NTRS1973

The radiometer transfer function for the AAFE composite two-frequency radiometer scatterometer

A model was developed for the switching radiometer utilizing a continuous method of calibration. Sources of system degradation were identified and include losses and voltage standing wave ratios in front of the receiver input. After computing the three modes of operation, expressions were developed for the normalized radiometer output, the minimum detectable signal (normalized RMS temperature fluctuation), sensitivity, and accuracy correction factors).

Moore, J. H.↗
NASA NTRS1974

Solar radiometry at millimeter wavelengths

In the area of resolution enhancement, the use of Fast Fourier Transform programs was investigated for possible application to millimeter wavelength maps of the sun. A difficulty arises with the La Posta maps in that they are limited to 35 arc-minutes square while the smeared out solar image is larger than that. A list of possible cometary emission lines near 13 millimeters is presented. Although preparation of the list was inspired by the appearance of Comet Kohoutek, the results are applicable to any future comet. The brightness temperature of the sun at 8.6 millimeters was measured using the moon as a calibration source. The result does not confirm a deep absorption feature as apparently observed by earlier workers.

Henze, W.↗
NASA NTRS1973

Design and performance characteristics of the vertical temperature profile radiometer /VTPR/ for atmospheric temperature soundings

Various design characteristics and performance achievements of the vertical temperature profile radiometer (VTPR) are discussed. It is shown that the VTPR provides a relative calibration accuracy of better than 0.1% rms of the full dynamic range and has been operating successfully in space on the ITOS spacecraft for more than eleven months. The absolute accuracy achievable between in-flight calibrations of 6 minutes, or between 2-hour calibrations using optical temperature correction factors, is better than an rms value of 0.15% of full scale. The radiometric correlation between the VTPR in-flight calibration source and a reference standard blackbody is better than an rms value of 0.5% of full scale.

Falbel, G.↗
NASA NTRS1974

Absolute brightness temperature measurements at 2.1-mm wavelength

Absolute measurements of the brightness temperatures of the Sun, new Moon, Venus, Mars, Jupiter, Saturn, and Uranus, and of the flux density of DR21 at 2.1-mm wavelength are reported. Relative measurements at 3.5-mm wavelength are also preented which resolve the absolute calibration discrepancy between The University of Texas 16-ft radio telescope and the Aerospace Corporation 15-ft antenna. The use of the bright planets and DR21 as absolute calibration sources at millimeter wavelengths is discussed in the light of recent observations.

Ulich, B. L.↗
NASA NTRS1974

A balloon-borne cryogenically cooled filter radiometer

The development of a cryogenically cooled filter radiometer for use with high altitude balloons is discussed. The radiometer has features which include the options for remote operation of two filter wheels each containing six filters at helium temperature and a cryogenic rotary chopper which may be run at 200 cycles per second or positioned open or closed, and a remotely operable chopped blackbody calibration source. The radiometer contains a ten inch diameter liquid nitrogen cooled Cassegrain telescope with nine individually filtered field stops in the focal plane. The telescope is mounted on a two-axis servo operated gimbal which is used to make sky scans under the control of an onboard programmer.

Debell, A. G.↗
NASA NTRS1974

Low-background air-infrared telescope for balloon-borne infrared astronomy

The design and performance of a far-infrared telescope are discussed. The instrument is twenty centimeters in diameter and has excellent operating characteristics at 100 microns. The principal features of the telescope are summarized. A diagram of the system is provided. The telescope completed two sucessful balloon flights in which the planets Mars and Saturn were used as calibration sources. Observations were made of the H2 regions W 3, Orion A, NGC 2024, and the bright infrared galaxy M 82.

Low, F. J.↗
NASA NTRS1975

The X-band low noise antenna measurement cone

An X-band low-noise receiving cone with 17-MHz instantaneous bandwidth was built to evaluate the 26-m antenna at the Venus Station (DSS 13), Goldstone, California, at X-band frequencies, and also to provide a means for precise radio source calibrations in this frequency range. These measurments are necessary to provide more accurate antenna gain performance calibrations for the 64-m antenna subnet. The zenith system temperatures with the cone on the ground and on the antenna are 17.5 and 20.8 K, respectively.

Reid, M. S.↗
NASA NTRS1976

DSN research and technology support

The activities of the Venus Station (DSS 13) and the Microwave Test Facility (MTF) during the period April 19 through June 13, 1976, are discussed and progress noted. Continuing reliability testing and computer program refinement of the remote controlled, unattended automated pulsar observing station is noted, along with routine observations of 17 pulsars. Radar observations of a geostationary satellite are reported, along with the routine automatic testing of the stability of the DSS 13 maser-receiving system. Additional testing of thermal characteristics of semiflexible coaxial cables is reported, along with phase stabilization measurements thereon. Routine support of the planetary radio astronomy experiment, with 43.25 hours of observations of Jupiter and various radio calibration sources, is reported, along with 18.75 hours of differential VLBI observations in conjunction with Australia, DSS 43. Modifications of the clock synchronization winterization system are reported, along with a discussion of the activities of the DSN High-Power Transmitter Maintenance Facility.

Jackson, E. B.↗
NASA NTRS1978

Imaging Proportional X-ray Counter for HEAO

The HEAO-B Imaging Proportional Counter (IPC) is an X-ray imaging instrument designed for use in the High Energy Astronomy Observatory - Mission B (HEAO-B) X-ray Telescope. It measures the spatial location of individual X-ray photons by the risetime method and energy of photons by pulse height analysis. The IPC can locate photons in the energy range 0.2 to 4 keV to within 1 mm and provides 5 bits of energy level information. Each measured X-ray event is also time tagged with 7 bits of temporal data. The IPC also includes an in-flight-calibration source and uses a gas control system that maintains the counter gas density constant to an accuracy of 0.25 percent.

Humphrey, A.↗
NASA NTRS1978

Far infrared spectrophotometry of Jupiter and Saturn

Infrared spectral measurements of Mars, Jupiter, and Saturn were obtained from 100 to 470 kaysers and, by taking Mars as a calibration source, brightness temperatures of Jupiter and Saturn were determined with approximately 5 kayser resolution. Internal luminosities were determined from the data and are reported to be approximately 8 times 10 to the minus tenth power of the sun's luminosity for Jupiter and approximately 3.6 times 10 to the minus tenth power of the sun's luminosity for Saturn. Comparison of data with spectra predicted by models suggests the need for an opacity source in addition to gaseous hydrogen and ammonia to help explain Jupiter's observed spectrum in the vicinity of 250 kaysers.

Erickson, E. F.↗
NASA NTRS1981

Very high resolution observations of SS433 at 10.65 GHz

Observations of SS433 made on June 12, 1979, from West Germany, Massachusetts, and West Virginia are discussed. It is noted that SS433 did not show fringes on any baseline although all the calibration sources were seen at their expected strengths. The measured total flux density of SS433 was found to be approximately 0.5 Jy, consistent with previous observations. The source was observed by on-offs at each telescope, which indicates that they were all pointed properly during the observations. The absence of fringes is not attributed to poor observing conditions or instrumental difficulties. It is concluded that if all the 10.65 GHz radiation emanates from a single component, then that component is at least 0.005 arcsec (approximately 10 to the 14th cm) in size. The measurements made on more sensitive intercontinental baselines indicate that there is no component of SS433 smaller than 0.001 arcsec emitting 10.65 GHz radiation above a level of 50 mJy.

Geldzahler, B. J.↗
NASA NTRS1982

Multispectral Linear Array (MLA) science and technology program

A Goddard Space Flight Center program of science studies and technology development to provide the basis for future earth observation sensors employing multispectral linear array (MLA) technology is described. Establishment of MLA performance parameters and performance modeling make up the primary science activities. Critical technologies being developed include: short-wave infrared (SWIR) detector arrays, visible/and near infrared detector arrays, and passive cryogenic coolers. Supporting activities include: test and field instrument development, focal plane research and assessment laboratory, system simulation laboratory, calibration sources and techniques, optics, and thermal infrared arrays.

Barnes, W. L.↗
NASA NTRS1984

Study of proton and neutron activation of metal samples in low Earth orbit

Progress in the following activities has been made: the analysis of the gamma ray spectra taken from samples flown in Spacelab 2; the search for and review of neutron and proton activation cross sections needed to analyze the results of the Long Duration Exposure Facility (LDEF) activation measurements; the consideration given to data analysis of the LDEF and Spacelab 2 samples; the plan to measure relevant cross sections with nuclear accelerator measurements; and the preparation of an extended gamma ray calibration sources continues through planning and direct measurement of gamma ray efficiency for a Ge(Li) as a function of position along the surface of the detector housing.

Laird, C. E.↗
NASA NTRS1984

Study of proton and neutron activation of metal samples in low Earth orbit

The analysis of the gamma-ray spectra taken from samples flown in Spacelab 1; the search for and review of neutron and proton activation cross-sections needed to analyze the results of the Long Duration Exposure Facility (LDEF) activation measurements; additional calculations of neutron induced activation for the LDEF samples; the data analysis plan for the LDEF and Spacelab 2 samples; the measurement of relevant cross-sections with activation of samples of V, Co, In, and Ta at the Indiana University Cyclotron Facility; and the preparation of an extended gamma-ray calibration source through the development of a proper technique to accurately deposit equal quantities of radioactive material onto a large number of point on the source are discussed.

Laird, C. E.↗
NASA NTRS1985

Microwave blackbodies for spaceborne receivers

The properties of microwave blackbody targets are explained as they apply to the calibration of spaceborne receivers. Also described are several practicable, blackbody targets used to test and calibrate receivers in the laboratory and in the thermal vacuum chamber. Problems with the precision and the accuracy of blackbody targets, and blackbody target design concepts that overcome some of the accuracy limitations present in existing target designs, are presented. The principle of the Brewster angle blackbody target is described where the blackbody is applied as a fixed-temperature test target in the laboratory and as a variable-temperature target in the thermal vacuum chamber. The reflectivity of a Brewster angle target is measured in the laboratory. From this measurement, the emissivity of the target is calculated. Radiatively cooled thermal suspensions are discussed as the coolants of blackbody targets and waveguide terminations that function as calibration devices in spaceborne receivers. Examples are given for the design of radiatively cooled thermal suspensions. Corrugated-horn antennas used to observe the cosmic background and to provide a cold-calibration source for spaceborne receivers are described.

Stacey, J. M.↗
NASA NTRS1985

Photofraction of a 5 cm x 2 cm BGO scintillator

The photofraction of a 5.1 cm x 2.0 cm bismuth germanate (BGO) scintillator was measured over a gamma-ray energy range of 0.2 to 6.1 MeV. Several methods, used to minimize the effect of room scattering on the measurement, are discussed. These include a gamma-gamma coincidence technique, a beta-gamma coincidence technique, and the use of sources calibrated with a standard 7.6 cm x 7.6 cm sodium iodide scintillator.

Dunphy, P. P.↗