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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Ultraviolet Spectra of Two Magnetic White Dwarfs and Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey and Ultraviolet Absorptions in the Spectra of DA White Dwarfds

Research under NASA Grant NAG5-287 has carried out a number of projects in conjunction with the International Ultraviolet Explorer (IUE) satellite. These include: (1) studies of the UV spectra of DA white dwarfs which show quasi-molecular bands of H2 and H2(+); (2) the peculiar star HR6560; (3) the UV spectra of two magnetic white dwarfs that also show the quasi-molecular features; (4) investigations of the UV spectra of subluminous stars, primarily identified from visual wavelength spectroscopy in the Kiso survey of UV excess stars, some of which show interesting metal lines in their UV spectra; and (5) completion of studies of UV spectra of DB stars. The main result of this research has been to further knowledge of the structure and compositions of subluminous stars which helps cast light on their formation and evolution.

Wegner, Gary A.↗
NASA NTRS1991

Reflectance spectra of Fe(2+)-Mg(2+) disordered pyroxenes: Implications to remote-sensed spectra of planetary surfaces

The reflectance spectra of Fe(2+)-Mg(2+) disordered orthopyroxenes are relevant to surfaces of terrestrial planets onto which basaltic magma has been extruded. If cooling rates of basalt lava flows were fast, equilibrium iron intersite partitioning may not have been achieved so that abnormal enrichments of Fe(2+) ions in M1 sites would occur. The two intense pyroxene Fe(2+) site CF bands in the 1 micron and 2 micron regions would continue to dominate the the reflectance spectra so that the pyroxene composition and structure type would be readily identified in telescopic spectral profiles. However, abnormal intensification of the Fe(2+)/M1 site CF band at 1.20 microns could lead to the false identification of olivine in remote sensed spectra because in pyroxene-olivine mixtures the inflection around 1.20 microns is the only spectral feature for detecting the presence of olivine. The identification of iron-bearing plagioclase feldspars, too, would be obscured by the pyroxene Fe(2+)/M1 site CF band at 1.20 microns. Such interference would be a major problem if in situ reflectance spectra could be measured on the surface of Venus where ambient temperatures are as high as 475 C. Disordering of Fe(2+) and Mg(2+) ions comparable to that in the orthopyroxenes used in this spectral chemical study might be expected in low Ca pyroxenes occurring on the Venusian surface. Researchers conclude that Fe(2+)/M1 site spectral features need to be carefully assessed in remote-sensed spectra before deductions are made about the presence of olivine on planetary surfaces.

Burns, Roger G.↗
NASA NTRS1976

Comparison of remotely sensed continental-shelf wave spectra with spectra computed by using a wave refraction computer model

An initial attempt was made to verify the Langley Research Center and Virginia Institute of Marine Science mid-Atlantic continental-shelf wave refraction model. The model was used to simulate refraction occurring during a continental-shelf remote sensing experiment conducted on August 17, 1973. Simulated wave spectra compared favorably, in a qualitative sense, with the experimental spectra. However, it was observed that most of the wave energy resided at frequencies higher than those for which refraction and shoaling effects were predicted, In addition, variations among the experimental spectra were so small that they were not considered statistically significant. In order to verify the refraction model, simulation must be performed in conjunction with a set of significantly varying spectra in which a considerable portion of the total energy resides at frequencies for which refraction and shoaling effects are likely.

Poole, L. R.↗
NASA NTRS1972

Spectra of type I supernovae. I - Generalities. II - Interpretation of the spectra of Sn 1960 in NGC 4496 from 8 to 20 days after the maximum of luminosity.

In the late stages of type I supernovae evolution (t greater than 50 days) the spectrum is without doubt an emission line spectrum, but in the early stages it is difficult to tell if an emission line spectrum is observed, or a continuum spectrum modified by the overlaying absorption formed in the outer layers. The mechanism of formation of the observed spectra, the physical conditions in the shell, different possible sources of heating of the shell, identification of the lines, and theoretical computations of the line intensities are discussed. An attempt is made to interpret the set of spectra assuming that a spectrum of widely broadened emission lines truncated by an overlaying absorption is seen. The absorption spectrum is first studied. An identification for the emission lines is proposed, and their intensity on the observed spectra is tentatively estimated. These identifications have to be justified by the theoretical computations of a model of the shell.

Gordon, C.↗
NASA NTRS1982

Stratospheric N2O mixing ratio profile from high-resolution balloon-borne solar absorption spectra and laboratory spectra near 1880/cm

A nonlinear least-squares fitting procedure is used to derive the stratospheric N2O mixing ratio profile from balloon-borne solar absorption spectra and laboratory spectra near 1880/cm. The atmospheric spectra analyzed here were recorded during sunset from a float altitude of 33 km with the University of Denver's 0.02/cm resolution interferometer near Alamogordo, N.M. (33 deg N) on Oct. 10, 1979. The laboratory data are used to determine the N2O line intensities. The measurements suggest an N2O mixing ratio of 264 ppbv near 15 km, decreasing to 155 ppbv near 28 km.

Rinsland, C. P.↗
NASA NTRS1988

Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey and Systematic Reanalysis of the Archived Ultraviolet Spectra of White Dwarfs Observed with the IUE Satellite Under the Astrophysics Data Program (ADP)

Recent research under NASA grant NAG5-971 consisted of the performance of two projects in conjunction with the International Ultraviolet Explorer (IUE) satellites. These are: (1) to look at the ultraviolet spectra of subluminous stars identified from visual wavelength spectroscopy that had been originally discovered from the Kiso Schmidt survey for ultraviolet excess stars and (2) to carry out a systematic reanalysis of the archived IUE spectra of white dwarfs. This report presents information on the progress of the re-reduction of over 600 IUE white dwarf spectra and their subsequent analysis employing model atmospheres and the observation of the Kiso ultraviolet excess stars.

Wegner, Gary A.↗
NASA NTRS1990

Reflectance spectra of mafic silicate-opaque assemblages with applications to meteorite spectra

The addition of fine-grained magnetite to mafic silicate spectra can impart not only an overall blue slope, but also lower overall reflectance and band intensities. The reflectance spectra of the CO and CV magnetite-bearing carbonaceous chondrites are noted to exhibit many of these features; the low band depths of these meteorites suggest that an additional dark, neutral phase, such as ordered carbon, is present. Carbon + mafic silicate spectra possess a red overall slope at low amorphous carbon concentrations. The parent bodies of some of the darkest meteorites should exhibit spectral features attributable to mafic silicates.

Cloutis, Edward A.↗
NASA NTRS1972

Spectra and cross spectra of solar wind parameters from Mariner 5

The spectra of the radial (V sub R) and nonradial (V sub T, V sub N) velocity components of the solar wind, the proton density (rho) and the proton thermal speed (W), show increasing power with increasing period up to a period of about 1 day. The powers tend to level off above 1 day except for that of V sub R which continues to increase up to a period of 10 days. At all periods, the power is V sub R is greater than that in V sub T V sub N, and W, and the difference becomes very large at the longest periods because of the increasing power in V sub R. The powers in V sub T V sub N, and W are similar at all periods. The cross spectra reveal a sharp change in behavior at periods above and below approximately 1 day, suggesting that two distant types of physical processes must dominate above and below this dividing period. In general, the coherences at the long periods are larger than at the short periods suggesting that the physical situation in the long period regime may be simpler than in the short period regime where multiple processes appear to be required to account for the low coherences.

Goldstein, B.↗
NASA NTRS1975

Spectra and structure of organophosphorus compounds. XII - Infrared and Raman spectra of /CH3/2PH and /CD3/2PH

The vibrational spectra of (CH3)2PH and (CD3)2PH have been studied and assignments made. In the infrared, the region between 4000 and 33 wavelength/cm was recorded for the gaseous and solid states, while Raman spectra from 3500 to 10 wavelength/cm in the gaseous, liquid and solid states were observed. There is some evidence of weak hydrogen bonding, based on the behavior of the phosphorus-hydrogen stretching and bending modes. There also appears to be considerable interaction between the methyl rocking and phosphorus-carbon stretching modes. The a double prime and a prime torsional modes appear to be accidentally degenerate at 182 and 142 wavelength/cm for the 'light' and 'heavy' compounds, respectively. This gives barriers of 2.14 and 2.30 kcal/mole, respectively.

Durig, J. R.↗
NASA NTRS1977

Analysis of torsional spectra of molecules with two internal C/3v/ rotors. III - Far-infrared and gas phase Raman spectra of dimethylamine-d0, -d3, and -d6

The Raman spectra of gaseous dimethylamine-d0, -d3, and -d6 have been recorded between 0 and 4000/cm. The far-infrared spectra have been recorded between 300 and 100/cm. Considerable torsional data are reported and used to characterize the torsional potential function based on a semi-rigid model. The average effective V3 for the dimethylamines was found to be 1052 plus or minus 12/cm. The cos-cos coupling term was approximately 15% of the effective V3, whereas the sine-sine coupling term was of an order of magnitude smaller for (CH3)2NH and (CD3)2NH. However, for the mixed isotope the sine-sine term was found to be negligible and the cos-cos about one-half the value obtained for the other two isotopes.

Durig, J. R.↗
NASA NTRS1980

Documentation for the machine-readable version of an atlas of ultraviolet stellar spectra and a second atlas of ultraviolet stellar spectra from OAO 2 observations

The magnetic tape version of the Orbiting Astronomical Observatory 2 atlases of ultraviolet stellar spectra is described. The first file of the tape contains ultraviolet stellar fluxes for 164 bright stars in lambda the spectral region 1200 to 1300 A with resolutions of 22 A in the region from 3600 to 1850 A and 12 A in the region from 1850 to 1160 A. Files two and three contain spectra for 132 stars in the region lamba 1200 to 1850 A and 34 stars in the lambda region 1800 to 3600 A, respectively, with resolutions as stated above. The monochromatic flux is given in units of ergs cm(-2)s(-1) (-1) for all data.

Warren, W. H., Jr.↗
NASA NTRS1980

High temperature crystal field spectra of transition metal-bearing minerals - Relevance to remote-sensed spectra of planetary surfaces

It is pointed out that transition metal ions in silicate minerals, glasses, and crystalline and amorphous oxyhydroxides and salts contribute to the visible-near infrared spectral profiles of planetary surfaces. Investigations are conducted to obtain spectral information which might be helpful in the interpretation of the remote-sensed spectra of planetary surfaces. A description is presented of the results of high temperature crystal field spectral measurements of a variety of heated minerals containing Cr(3+), Fe(3+), Fe(++), and Mn(++) ions in different coordination symmetries, taking into account a correlation of the temperature-induced variations with those previously observed for octahedrally coordinated Fe(++)-bearing silicates. The employed experimental methods are also discussed, giving attention to the preparation of the samples, the determination of the absorption spectra, electron microprobe analyses, and the curve fitting procedure.

Parkin, K. M.↗
NASA NTRS1986

An example of scaling MST Doppler spectra using median spectra, spectral smoothing, and velocity tracing

Although automatic, computer scaling methods appeared at the start of the MST (mesosphere stratosphere troposphere) radar technique, there is a continuing need for scaling algorithms that perform editing functions and increase the sensitivity of radar by post processing. The scaling method presented is an adaptation of the method of scaling MST Doppler spectra presented by Rastogi (1984). A brief overview of this method is as follows: a median spectrum is calculated from several sequential spectra; the median noise value is subtracted from this derived spectrum; the median spectrum is smoothed; the detection/nondetection decision is made by comparing the smoothed spectrum to the variance of the smoothed noise; and if a signal is detected, then the half-power points of the smoothed echo spectrum are used to place limits on the evaluation of the first two moments of the unsmoothed median spectrum. In all of the above steps, the algorithm is guided by tracing the expected velocity range upward from the lowest range as far as possible. The method is discussed in more detail.

Green, J. L.↗