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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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NASA NTRS1978

Radial dependence of solar wind properties deduced from Helios 1/2 and Pioneer 10/11 radio scattering observations

Radio scattering measurements at 2.3 GHz, conducted over the heliocentric distance range of 1.7 to 180 solar radii, provide data for a study of the radial dependence of the solar wind characteristics. The data are obtained from the Helios 1 and 2 and the Pioneer 10 and 11 spacecraft. Spectral broadening measurements, together with angular broadening data for the spacecraft signal, indicate a value of 24 km/sec for the solar wind velocity at 1.7 solar radii. A velocity profile of the solar wind in the acceleration range is developed. In addition, phase scintillation measurements obtained suggest that the solar wind is slightly converging in the equatorial region between approximately 20 and 180 solar radii.

Woo, R.↗

NASA NTRS1978

Nuclear Science Symposium, 4th, and Nuclear Power Systems Symposium, 9th, San Francisco, Calif., October 19-21, 1977, Proceedings

Consideration is given to the following types of high energy physics instrumentation: drift chambers, multiwire proportional chambers, calorimeters, optical detectors, ionization and scintillation detectors, solid state detectors, and electronic and digital subsystems. Attention is also paid to reactor instrumentation, nuclear medicine instrumentation, data acquisition systems for nuclear instrumentation, microprocessor applications in nuclear science, environmental instrumentation, control and instrumentation of nuclear power generating stations, and radiation monitoring. Papers are also presented on instrumentation for the High Energy Astronomy Observatory.

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NASA NTRS1978

Evidence that cosmic gamma-ray bursts are galactic

Balloon observations registering scatter angles in a liquid scintillator have revealed gamma-ray bursts having energies as low as 10 to the -7th ergs per square cm. The burst distribution is graphed according to energy and frequency. The hypothesis that the bursts are galactic in origin is in good agreement with their small recorded energies and their predicted distribution on the graph.

White, R. S.↗

NASA NTRS1977

Design and performance of an actively collimated phoswich system for X-ray astronomy

The design and performance of a phoswich type scintillation detector system having 34 sq cm effective collecting area and a sensitivity of 3 x 10 to the -5th power photons/sq cm/s/keV for balloon-borne cosmic X-ray source observations are discussed. The various shield anticoincidence systems are evaluated for effectiveness in reduction of the system background. The total background of nominally 4 x 10 to the -4th power counts/sq cm/s/keV is analyzed and found to consist of aperture flux, K-escape X-rays from the shielding, leakage, and degradation of gamma-rays through the shielding, and several particle induced effects. The background analysis suggests an ultimate practical upper limit of about 8 x 10 to the -5th power counts/sq cm/s/keV might be attainable beyond which further sensitivity improvements will require increased collecting area or a basically differing design approach.

Matteson, J. L.↗

NASA NTRS1978

Measurements of the spectrum and energy dependence of X-ray transition radiation

The results of experiments designed to test the theory of X-ray transition radiation and to verify the predicted dependence of the characteristic features of the radiation on the radiator dimensions are presented. The X-ray frequency spectrum produced by 5- to 9-GeV electrons over the range 4 to 30 keV was measured with a calibrated single-crystal Bragg spectrometer, and at frequencies up to 100 keV with an NaI scintillator. The interference pattern in the spectrum and the hardening of the radiation with increasing foil thickness are clearly observed. The energy dependence of the total transition-radiation intensity was studied using a radiator with large dimensions designed to yield energy-dependent signals at very high particle energies, up to E/mc-squared approximately equal to 100,000. The results are in good agreement with the theoretical predictions.

Cherry, M. L.↗

NASA NTRS1978

New limits on gamma-ray bursts

Two balloon flights of large-area scintillation crystal detector arrays indicate that the rate of weak gamma-ray bursts is significantly below that expected from a uniform distribution of burst sources. This result, combined with the data from stronger bursts, gives strong evidence for a galactic confinement of burst sources. Reasonable models of confinement limit the intrinsic radiated energy per burst to the order of 10 to the (39th to 41st power) ergs.

Fishman, G. J.↗

NASA NTRS1978

X-ray spectrometer experiment aboard the ISEE-C /Heliocentric/ spacecraft

This experiment is designed to provide continuous coverage of solar flare X-ray bursts and transient cosmic gamma-ray bursts. A proportional counter and a scintillation detector together cover the energy range from 5 to 228 keV with good sensitivity, large dynamic range, and high temporal resolution. This experiment provides data storage capability and good absolute timing so that in conjunction with similar experiments on other spacecraft, accurate source locations can be obtained for cosmic gamma-ray bursts.

Anderson, K. A.↗

NASA NTRS1978

The University of Chicago cosmic ray electrons and nuclei experiment on the H spacecraft

The University of Chicago instrument on the Heliocentric spacecraft (MEH experiment) will measure the energy spectrum of cosmic electrons in the range 5-400 MeV. In addition, the energy spectra and relative abundances of nuclei from protons to the iron group, with energies ranging from 30 MeV/n to 15 GeV/n, will be determined. Primary scientific objectives involve the study of the long and short term variability of these components as a probe of the structure of the heliosphere. Particles are identified by multiparameter analysis using the pulse height analyzed signals from eight active detectors - silicon solid state, plastic and crystal scintillators are solid and gas Cerenkov counters. Data return is optimized by a three level priority logic scheme.

Meyer, P.↗

NASA NTRS1977

Measurements of the solar wind using spacecraft radio scattering observations

This paper reviews radio scattering measurements of the solar wind carried out with coherent, monochromatic, and point-source spacecraft signals. The observed phenomena which include spectral and angular broadening, and phase as well as intensity scintillations, have provided measurements of the solar wind previously not available from radio astronomical observations. These cover a wide range of heliocentric distances (as close as 1.7 solar radii), and large- as well as small-scale electron density fluctuations.

Woo, R.↗

NASA NTRS1978

Experimental results on mass-thickness distribution in spacecraft equipment

A technique is described for evaluating the shielding properties of spacecraft equipment with respect to cosmic radiation. A gamma-ray source is used in conjunction with a scintillation detector to determine mass-thickness distribution both in plane geometry for equipment units, and in spherical geometry for given points within the spacecraft. Equations are presented for calculating mass-thickness distribution functions, and the results are compared with experimental measurements.

Bodin, V. V.↗

NASA NTRS1978

The high-energy pulsed X-ray spectrum of HER X-1 as observed with OSO-8

Her X-1 was observed from 1977 August 30 to September 10 using the High-Energy X-Ray Scintillation Spectrometer on board the OSO-8 satellite. The observation, during which the source was monitored continually for nearly an entire ON-state, covered the energy range from 16 to 280 keV. Pulsed flux measurements as a function of binary orbit and binary phase are presented for energies between 16 and 98 keV. The pulsed flux between 16 and 33 keV exhibited a sharp decrease following the fourth binary orbit and was consistent with zero pulsed flux thereafter. The pulsed spectrum was fitted with a power law, a thermal spectrum without features, and a thermal spectrum with a superposed gaussian centered at 55 keV. The latter fit has the smallest value of chi - squared per degree of freedom, and the resulting integrated line intensity is 1.5 superscript + 4.1 subscript - 1.4 x .001 photons s superscript-1 cm superscript-2 for a width of 3.1 superscript + 9.1 subscript -2.6 keV. This result, while of low statistical significance, agrees with the value observed by Trumper (1978) during the same On-state.

Maurer, G. S.↗

NASA NTRS1979

Low intensity X-ray and gamma-ray imaging device

A radiation to visible light converter is combined with a visible light intensifier. The converter is a phosphor or scintillator material which is modified to block ambient light. The intensifier includes fiber optics input and output face plates with a photocathode-microchannel plate amplifier-phosphor combination. Incoming radiation is converted to visible light by the converter which is piped into the intensifier by the input fiber optics face plate. The photocathode converts the visible light to electrons which are amplified by a microchannel plate amplifier. The electrons are converted back to light by a phosphor layer and piped out for viewing by the output fiber optics faces plate. The converter-intensifier combination may be further combined with its own radiation source or used with an independent source.

Yin, L. I.↗

NASA NTRS1979

High energy X-ray observations of BL lacertae objects

BL Lac objects are of considerable current interest both because they were recently realized to be a new class of objects and because they were found to be similar in many significant respects to QSOs and Seyfert Galaxies. Since at least one model for the X-ray emission predicts a flattening of the X-ray spectrum above a few keV, several of these sources were studied using the high energy scintillation telescopes on OSO-8 and Ariel-5. With the possible exception of Markaryan 421, only upper limits were obtained for the X-ray emission in the energy ranges 25-60 and 60-130 keV, thereby imposing constraints on any spectral breaks.

Coe, M. J.↗

NASA NTRS1979

X-ray observations of AM Herculis from OSO-8

The white dwarf binary system AM Herculis (2A1815+500) was observed in X-rays at both low energies (E less 10 keV) and higher energies. The exact shape of the spectrum, particularly at the higher energies, has yet to be determined. Results from the high energy scintillation spectrometer on OSO-8 are presented. These are combined with results published elsewhere obtained concurrently with the proportional counter on the same satellite, thereby giving for the first time coincident observations of AM Her over the range 2 to 250 keV.

Coe, M. J.↗

NASA NTRS1978

Processing techniques development, volume 3

The author has identified the following significant results. Analysis of the geometric characteristics of the aircraft synthetic aperture radar (SAR) relative to LANDSAT indicated that relatively low order polynominals would model the distortions to subpixel accuracy to bring SAR into registration for good quality imagery. Also the area analyzed was small, about 10 miles square, so this is an additional constraint. For the Air Force/ERIM data, none of the tested methods could achieve subpixel accuracy. Reasons for this is unknown; however, the noisy (high scintillation) nature of the data and attendent unrecognizability of features contribute to this error. It is concluded that the quadratic model would adequately provide distortion modeling for small areas, i.e., 10 to 20 miles square.

Landgrebe, D. A.↗

NASA NTRS1978

Global crop production forecasting data system analysis

The author has identified the following significant results. Findings led to the development of a theory of radiometric discrimination employing the mathematical framework of the theory of discrimination between scintillating radar targets. The theory indicated that the functions which drive accuracy of discrimination are the contrast ratio between targets, and the number of samples, or pixels, observed. Theoretical results led to three primary consequences, as regards the data system: (1) agricultural targets must be imaged at correctly chosen times, when the relative evolution of the crop's development is such as to maximize their contrast; (2) under these favorable conditions, the number of observed pixels can be significantly reduced with respect to wall-to-wall measurements; and (3) remotely sensed radiometric data must be suitably mixed with other auxiliary data, derived from external sources.

Castruccio, P. A.↗

NASA NTRS1979

On the variability of extragalactic sources in the decimeter range and their correlation with galactic structures

It is shown that all of the extragalactic radio sources presently known are variable in the decimeter range (lambda or = 30 cm) and are projected on the large continuum radio structure of the galaxy: loops, spurs, ridges. Probability that coordinates could coincide is or = 10 to the minus 7 power. The variations in the intensity are explained by scintillations (regime of focusing radiation) on the large-scale irregularities of electron density in the medium of loops, spurs and ridges with the dimension a magnitude of approximately 10 to the 13th power cm. A correlation of the characteristics of radiation of the sources with their position relative to the galactic loop is considered. Based on the known experimental data, it is shown that the angle of scattering of extragalactic radiation and the dispersion measures of pulsars projecting on the loops is considerably larger than those of the sources lying outside the loops.

Shapirovskaya, N. Y.↗

NASA NTRS1979

Study of mass flow distribution and chemical composition of comets from solar induced X-ray fluorescence

The expected performance of an X-ray detector as an instrument aboard a mission to a comet was evaluated. The functions of the detector are both nondispersive analysis of chemical composition and measurement of mass flow from the comet nucleus. Measurements are to be carried out at a distance from the comet. The approach distances considered are of the order of 1000 km and 100 km. A new type of X-ray detector, a proportional scintillation detector, is considered as an X-ray counter for nondispersive elemental analysis.

Gorenstein, P.↗