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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 415 records · Page 23
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NASA NTRS1980

Simultaneous far-infrared, near-infrared, and radio observations of OH/IR stars

Simultaneous far-infrared, near-infrared, and radio observations have been made of five infrared stars which show OH maser emission at 1612 MHz. These stars have very thick circumstellar dust shells and are not seen optically. The data permit a direct comparison of the far-infrared and maser emission from these sources, which strongly supports the hypothesis that the maser emission is pumped by 35 micron photons. A comparison with data obtained at earlier epochs suggests that the maser emission is saturated. The infrared and radio data are used together with estimates of the source distances to determine the luminosities and mass loss rates for these objects. The luminosities lie in the range 2000-30,000 solar luminosities and are consistent with either Mira variable or M supergiant classifications for the underlying stars. The estimated mass loss rates lie between 0.000005-0.00007 solar mass/year.

Werner, M. W.↗
NASA NTRS1981

Some aspects of analytical chemistry as applied to water quality assurance techniques for reclaimed water: The potential use of X-ray fluorescence spectrometry for automated on-line fast real-time simultaneous multi-component analysis of inorganic pollutants in reclaimed water

The potential use of isotopically excited energy dispersive X-ray fluorescence (XRF) spectrometry for automated on line fast real time (5 to 15 minutes) simultaneous multicomponent (up to 20) trace (1 to 10 parts per billion) analysis of inorganic pollutants in reclaimed water was examined. Three anionic elements (chromium 6, arsenic and selenium) were studied. The inherent lack of sensitivity of XRF spectrometry for these elements mandates use of a preconcentration technique and various methods were examined, including: several direct and indirect evaporation methods; ion exchange membranes; selective and nonselective precipitation; and complexation processes. It is shown tha XRF spectrometry itself is well suited for automated on line quality assurance, and can provide a nondestructive (and thus sample storage and repeat analysis capabilities) and particularly convenient analytical method. Further, the use of an isotopically excited energy dispersive unit (50 mCi Cd-109 source) coupled with a suitable preconcentration process can provide sufficient sensitivity to achieve the current mandated minimum levels of detection without the need for high power X-ray generating tubes.

Ling, A. C.↗
NASA NTRS1980

Effects of low energy proton, electron, and simultaneously combined proton and electron environments in silicon and GaAs solar cells

Degradation of silicon and GaAs solar cells due to exposures to low energy proton and electron environments and annealing data for these cells are discussed. Degradation of silicon cells in simultaneously combined electron and low energy proton environments and previous experimental work is summarized and evaluated. The deficiencies in current solar array damage prediction techniques indicated by these data and the relevance of these deficiencies to specific missions such as intermediate altitude orbits and orbital transfer vehicles using solar electric propulsion systems are considered.

Horne, W. E.↗
NASA NTRS1981

Simultaneous observations of active galactic nuclei with IUE

The IUE observations of four active nuclei were coordinated with radio, infrared, and X-ray measurements to obtain simultaneous determinations of their continuous spectra. The results for the BL Lac objects 0735+178 and I Zw 187 indicate sufficient UV and X-ray fluxes to ionize any gas. Comparison of the X-ray measurements with the extrapolated optical UV continuum show a definite X-ray excess for I Zw 187 but none for the other BL Lac object.

Bregman, J. N.↗
NASA NTRS1980

Simultaneous wave and particle observations in the auroral kilometric radiation source region

Simultaneous observations from the topside sounder and the soft particle spectrometer onboard the ISIS 1 satellite reveal that very specific conditions on the local electron density and the energetic electron distributions must both occur in the auroral kilometric radiation (AKR) source region. Such regions are associated with inverted V electron precipitation and with depletions in the local electron density. The electron velocity distribution functions obtained near the inverted V peak were found to increase near several keV energy with increasing velocity as required for plasma instability. The electron density observed near the inverted V peak was too high to support AKR for three events investigated, however, and the AKR source was identified with the edge of the inverted V where the density was low (less than or equal to 30/cu cm) in each case. Whereas this density depletion can extend deep into the ionosphere (approximately 1500 km altitude), the severe depletion associated with the AKR density cavity is restricted to higher altitudes (greater than 2750 km for an event studied in detail).

Benson, R. F.↗
NASA NTRS1980

AM Herculis - Simultaneous X-ray, optical, and near-IR coverage

A 6 hour X-ray pointing at AM Her using the HEAO 1 satellite is correlated with simultaneous broadband V and I photometry and visual circular polarimetry. The absence of correlations on either a flickering or an orbital time scale implies distinct regions for the visual and X-ray emission. Significant changes in the light curves are observed from one binary cycle to the next.

Szkody, P.↗
NASA NTRS1980

Simultaneous radiation damage and annealing of GaAs solar cells

In this report, concepts and equations are developed to describe the simultaneous radiation damage and annealing of solar cells. The annealing characteristics of three types of defects are employed to study three examples of continuous irradiation and annealing. One example shows that the effective damage could be reduced by a factor of fifty. The difficulty of a laboratory experiment properly simulating the effects in space are discussed. Potential advantages of continuous annealing such as reduction of stable defect formation and omission of radiation cover glasses are presented.

Heinbockel, J. H.↗
NASA NTRS1981

Quasi-simultaneous observations of BL Lac object Mrk 501 in X-ray, UV, visible, IR, and radio frequencies

Observations in the X-ray, UV, visible, IR and radio regions of the BL Lac object Mrk 501 made over the course of two months are reported. The measurements were made with the A2 experiment on HEAO 1 (X-ray), the SWP and LWR cameras on IUE (UV), the 5-m Hale telescope (visible), the 2.5-m telescope at Mount Wilson (IR), the NRAO 92-m radio telescope at Green Bank (4750 MHz) and the 46-m radio telescope at the Algonquin Observatory (10275 and 10650 MHz). The quasi-simultaneously observed spectral slope is found to be positive and continuous from the X-ray to the UV, but to gradually flatten and possibly turn down from the mid-UV to the visible; the optical-radio emission cannot be accounted for by a single power law. The total spectrum is shown to be compatible with a synchrotron self-Compton emission mechanism, while the spectrum from the visible to the X-ray is consistent with synchrotron radiation or inverse-Compton scattering by a hot thermal electron cloud. The continuity of the spectrum from the UV to the X-ray is noted to imply a total luminosity greater than previous estimates by a factor of 3-4.

Kondo, Y.↗
NASA NTRS1981

Simultaneous measurements of magnetotail dynamics by IMP spacecraft

Pressure in the magnetotail is investigated using observations obtained by IMP spacecraft. Using combined field and plasma data, the approximate balance of pressure between the high beta plasma sheet and the low beta tail lobes is demonstrated. The changes in this pressure during substorms and the characteristics of the plasma and field that produce it are discussed. A distance of about 15 earth radii separates an inner region where the plasma sheet thins during the hour before substorm onset from an outer region where the plasma sheet thins within 5 or 10 min of the time of onset. Substorm onset and plasma sheet expansion in the inner region are simultaneous if the spacecraft is near the equatorial plane. This expansion may be delayed as much as a few tens of minutes if the spacecraft is at high latitudes.

Fairfield, D. H.↗
NASA NTRS1981

Simultaneous measurements of NO/x/, NO, and O3 production in a laboratory discharge - Atmospheric implications

Simultaneous measurements of NO(x) (NO + NO2), NO, and O3 production in a laboratory discharge show that within the uncertainties of the experiment, all of the NO(x) produced was NO, and no detectable enhancement of O3 after the discharge was observed. The laboratory experiments described gave an NO production rate of 5 + or - 2 x 10 to the 16th molecules/joule mole for a 100,000-1,000,000 joules/m spark. Assuming that the global dissipation of lightning energy is about 10 to the -8th joules/sq cm per sec (Dawson, 1980; and Hill et al., 1980), the NO production rate results in a global source of NO due to lightning of about 1.8 Mt(N)/yr, which is considerably lower than earlier estimates. This lower value for NO(x) production by lightning suggests that NO(x) emissions from anthropogenic sources, estimated to be at least 20 MT(N)/yr, may be the dominant source of NO(x) to the global troposphere. Furthermore, since most of the anthropogenic sources of NO(x) are located in the Northern Hemisphere, this new interpretation of the relative source strengths of this species favors a highly skewed asymmetric distribution of NO(x).

Levine, J. S.↗
NASA NTRS1981

Simultaneous X-ray and optical observations of an Ursae Majoris during a low state

In November 1975, AN UMa was detected as a soft X-ray source with a 0.1-0.4 keV flux which was modulated with the orbital cycle. In order to investigate further this orbital dependence and to correlate it with existing photometric and spectroscopic observations to aid in determining the geometry of the system, simultaneous X-ray and optical observations were made throughout several cycles of AN UMa. The system was in a low optical state during the observations. The X-ray observations were made with the Imaging Proportional Counter on the Einstein Observatory, yielding measurements over an available energy range of 0.1-4 keV. Attention is given to total X-ray flux, the X-ray light curve, optical and infrared data, and model implications.

Szkody, P.↗
NASA NTRS1981

Simultaneous in-flight calibrations of the Galileo science platform and attitude control subsystems

This paper presents a design metholodology and simulation study results for a combined star scanner-gyro-scan platform in-flight calibration for the dual spin Galileo spacecraft. The design process involves three separate parts: the construction of an error model, development of the calibration model, and the selection of the appropriate estimation technique. The major innovative contribution lies in the development of the first two parts which are unique to the Galileo design. A unified procedure has been developed to allow simultaneous calibration of the three subsystems. However, provisions are also made in the software to calibrate each subsystem separately when the necessary a priori information is available.

Lai, J. Y.↗
NASA NTRS1981

Simultaneous observations of energetic protons close to the bow shock and far upstream

Four upstream energetic proton events (30 keV-75 keV), which were simultaneously observed by the ISEE-1 and ISEE-3 satellites, are investigated. A comparison was made between the absolute flux values about 200 earth radii from the bow shock and the flux values several earth radii in front of the bow shock at two different energies. Close to the bow shock the particle distribution is more or less isotropic and indicates relatively strong scattering of these particles in the upstream wave field. At ISEE-3 between 100 and 200 earth radii upstream from the earth's bow shock, the particles move essentially scatter-free from the general bow shock direction. The proton differential intensity at ISEE-3 is a factor of about 4-15 less than at ISEE-1 at 30 keV. The spectra at ISEE-1 are steeper than the spectra at ISEE-3. Flux ratios and spectra are discussed in terms of a first order Fermi acceleration model with a diffusion coefficient increasing approximately linearly with energy and a free escape boundary at some distance upstream.

Scholer, M.↗
NASA NTRS1981

Changes in the high state of AM Herculis - A simultaneous X-ray, optical, polarimetric, and spectroscopic study

Simultaneous UBVR photometry, circular polarimetry, and high resolution spectroscopy observations (during May, 1979), coordinated with a monitor proportional counter and a solid state spectrometer, are reported for the cataclysmic variable AM Her, when it was in its normal 'high' state, where the mean visual magnitude was 12.5 mag versus 15 mag for the infrequent 'low' state. The circular polarization was always negative and had the smallest peak to peak amplitude yet reported. The emission lines He II 4686, H-beta, N III 4634, N III 4640-4641, C III 4650-4651, and He I 4713 present at least two components identified with the broad and sharp components of Greenstein at al. (1977). The radial velocity curve of the broad component shows a 50% reduction of amplitude in comparison to their values, and a third very broad component in 4686 is identified. No correlation between the optical photometry and 1-10 keV X-ray intensity was found on flickering time scales. Results of the observations are discussed within the framework of models with accretion onto one or both magnetic poles of the white dwarf.

Crosa, L.↗
NASA NTRS1981

Airborne simultaneous spectroscopic detection of laser-induced water Raman backscatter and fluorescence from chlorophyll a and other naturally occurring pigments

The airborne laser-induced spectral emission bands obtained simultaneously from water Raman backscatter and the fluorescence of chlorophyll and other naturally occurring waterborne pigments are reported here for the first time. The importance of this type data lies not only in its single-shot multispectral character but also in the application of the Raman line for correction or calibration of the spatial variation of the laser penetration depth without the need for in situ water attenuation measurements. The entire laser-induced fluorescence and Raman scatter emissions resulting from each separate 532-nm 10-nsec laser pulse are collected and spectrally dispersed in a diffraction grating spectrometer having forty photomultiplier tube detectors. Results from field experiments conducted in the North Sea and the Chesapeake Bay/Potomac River are presented. Difficulties involving the multispectral resolution of the induced emissions are addressed, and feasible solutions are suggested together with new instrument configurations and future research directions.

Hoge, F. E.↗
NASA NTRS1981

A new CT collimator for producing two simultaneous overlapping slices from one scan

A new CT collimator is developed which is capable of producing two simultaneous successive overlapping images from a single scan. The collimator represents a modification of the standard EMI 5005 collimator achieved by alternately masking one end or portions of both ends of the X-ray detectors at a 13-mm beamwidth so that a set of 540 filtered projections is obtained for each scan which can be separated into two sets of interleaved projections corresponding to views 3 mm apart. Tests have demonstrated that the quality of the images produced from these two projections almost equals the quality of those produced by the standard collimator from two separate scans. The new collimator may thus be used to achieve a speed improvement in the generation of overlapping sections as well as a reduction in X-ray dosage.

Kwoh, Y. S.↗
NASA NTRS1982

Simultaneous multifrequency observations of BL Lac objects and violently variable quasars

Ultraviolet spectra simultaneous with radio, infrared, optical, and X-ray measurements were obtained for three BL Lac objects and one violently variable quasar during several epochs (0735+178, BL Lac, IZw-187, and 3C446). A feature common to these objects is that the radio-mm continuum must steepen in the far-infrared region in order to connect smoothly to the IR-UV continuum. This indicates that synchrotron emission becomes optically thick in the mm or far-infrared region. The continuum of 3C446 and BL Lac steepen quite rapidly between the IR and UV spectra with slopes near unity. The X-ray emission in BL Lac, 3C446, and 0735+178 has a different origin from the IR-UV radiation, probably from the inverse Compton process. However, the synchrotron radiation is the probable source of X-ray emission in the X-ray bright BL Lac object IZw-187. In IZw-187, most of the energy emerges in the UV - X-ray region, while for the other sources, most of the energy emerges in the far infrared region.

Bregman, J. N.↗
NASA NTRS1982

Simultaneous calibrations of Voyager celestial and inertial attitude control systems in flight

A mathematical description of the data reduction technique used to simultaneously calibrate the Voyager celestial and inertial attitude control subsystems is given. It is shown that knowledge of the spacecraft limit cycle motion, as measured by the celestial and the inertial sensors, is adequate to result in the estimates of a selected number of errors which adversely affect the spacecraft attitude knowledge.

Jahanshahi, M. H.↗