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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 199 records · Page 11
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NASA NTRS1976

Spectroscopic observations of comet Kohoutek (1973f), 2

Spectroscopic observations of comet Kohoutek at the Asiago Astrophysical Observatory are described. Spectra cover six nights before perihelion and five nights after perihelion. The spectra of the coma and tail of comet Kohoutek are characterized by fairly strong, asymmetric H2O(+) emissions in the red and the near infrared spectral regions and by the appearance of the 01 forbidden lines at 6300-6364 A, already at heliocentric distance r=1.55 A.U. These peculiarities suggest that some differences in chemical abundances or in physical conditions exist between comet Kohoutek and other comets.

Benvenuti, P.↗
NASA NTRS1976

High dispersion spectroscopic observations of HD 153919 (3U 1700-37)

A spectrogram of HD 153919 taken in June 1975 at phase phi = 0.79 shows the following interesting features when compared to previously published line profiles: (1) increased central absorption or more extended blue wings for He II lambda 5411 A and lambda 4541 A; (2) a change in the P Cygni profile of H beta; (3) a change in the relative intensities of N III and C III in the emission complex lambda lambda 4630-4650 A; and (4) a previously unreported emission feature near lambda 5300 A. These observations indicate the presence of a variable stellar wind from the primary, changes in the emission measure of the line-forming region in the primary, and possible spectroscopic signatures of features in the extended expanding atmosphere of the primary or the wake of the secondary.

Dupree, A. K.↗
NASA NTRS1976

Spectroscopic detection and vertical distribution of HCl in the troposphere and stratosphere

HCl has been observed in both the troposphere and stratosphere from ground-based and airborne spectroscopic measurements of the 1-0 band at 3-micron wavelength. The results, which are specific to the HCl molecule in the gas phase, show a decreasing mixing ratio with altitude in the lower stratosphere. The stratospheric layer, which commences at about 15 km, reaches its maximum concentration at an altitude above 21 km (the limiting height of the observations to date). The local value for the volume mixing ratio at 21 km is 7 + or - 1 times 10 to the minus 10th. However, the zenith column abundance observed above 21 km implies that the mixing ratios at greater altitudes are unlikely to reach values much in excess of the local value at 21 km.

Farmer, C. B.↗
NASA NTRS1976

Spectroscopic photoelectric imaging Fabry-Perot interferometer - Its development and preliminary observational results

In order to observe extended astronomical objects at high spatial and spectral resolution, we have constructed a spectroscopic photoelectric imaging Fabry-Perot interferometer (SPIFI). Among the properties chosen for the instrument are an air-spaced, piezoelectrically scanned design allowing an accurately settable free spectral range and employing a single etalon of high finesse. Careful design of the etalon mountings and optical train preserves high light throughput. We either obtain spectra of single spatial elements with a photomultiplier or use an SEC vidicon detector to record a series of images through the interferometer while scanning the wavelength in discrete steps. The latter procedure yields sufficient information to reconstruct spectral features over the entire object. For the conditions assumed, either series of observations requires only a small fraction of a rotational period for Jupiter or Saturn, for example.

Smith, W. H.↗
NASA NTRS1976

Spectroscopic analysis of solar and cosmic X-ray spectra. I - The nature of cosmic X-ray spectra and proposed analytical techniques

X-ray spectroscopic techniques developed in the study of the temperature and density structure of the solar corona are reviewed as introduction to a discussion of the modifications in these techniques which will be required for the study of cosmic X-ray sources. The structure of the interstellar medium - the presence of interstellar grains, the presence of molecules, the ionization structure - are considered in relation to the X-ray opacity of the interstellar medium. The expected spectral structure of individual cosmic X-ray sources is reviewed with emphasis on galactic supernova remnants and galactic binary X-ray sources.

Walker, A. B. C., Jr.↗
NASA NTRS1977

Spectroscopic determination of electrical conductivity in an MHD duct from absolute intensity measurements

Measurements of the electrical conductivity in the NASA Lewis cesium seeded, H2-O2 MHD duct have been previously reported. In order to corroborate the above measurements and to analyze the possibility of nonuniform seed injection as a cause of the deviations, a spectroscopic investigation of the plasma conductivity has been undertaken. Transverse profiles of the absolute integrated intensity were measured from the optically thin lines of CSI-.5664 microns and .5636 microns. Radial profiles of emission coefficient were obtained from the measured transverse profiles of intensity by Abel inversion. Radial profiles of electrical conductivity were then obtained under two different assumptions. In the first, the Cs seed fraction is assumed uniform and equal to the measured flow rate at the time when the temperature and conductivity were obtained. In the second method, the local temperature and pressure are taken to be those given by a one-dimensional channel calculation including heat transfer and friction. In this case profiles of conductivity and seed fractions are obtained. The results of the two methods are compared to the previously measured conductivity.

Wang, S. Y.↗
NASA NTRS1977

A spectroscopic study of selected quasars with absorption redshifts greater than emission redshifts

Spectroscopic data are presented for seven quasars having absorption systems whose redshift is greater than that of emission lines. The objects examined include PKS 1229-02, 3C 298, 3C 205, B194, PHL 1222, 0736-06, and PKS 0119-04. The redshift systems of each quasar are described in detail, the empirical distribution of the relative numbers of absorption systems vs. emission-absorption redshift difference is determined, and errors in this distribution due to selection of the sample and to the incompleteness and inhomogeneity of the data are discussed qualitatively. Six groups of possibilities are considered for the origin of absorption systems with redshifts higher than the emission redshifts. It is concluded that two separate mechanisms must be invoked: intervening clouds bound in a cluster of galaxies where the quasar is embedded (for systems with an absolute relative velocity not exceeding about 3000 km/s) and gravitational acceleration of material ejected by the quasar (for systems with a relative velocity of at least 3000 km/s).

Weymann, R. J.↗
NASA NTRS1977

Spectroscopic determination of electrical conductivity in an MHD duct from absolute intensity measurements

Measurements of the electrical conductivity in the NASA Lewis cesium seeded, H2-O2 MHD duct made by applying a voltage across the channel from one end electrode to the other, measuring the current, and using the inner electrodes as probes to monitor the voltage distribution along the channel were found to be in good agreement with theory except at low combustion pressures and/or high ratios of seed/oxygen mass flows. To corroborate these measurements and to analyze the possibility of nonuniform seed injection as a cause of the above deviations, a spectroscopic investigation of the plasma conductivity was undertaken. Radial profiles of emission coefficient were obtained from measured transverse profiles of the absolute integrated intensity by Abel inversion. Radial profiles of electrical conductivity were then obtained under two different assumptions. In the first the Cs seed fraction is assumed uniform and equal to the measured flow rate at the time when the temperature and conductivity were obtained. In the second method the local temperature and pressure are taken to be those given by a one-dimensional channel calculation including heat transfer and friction. The results of the two methods are compared to the previously measured conductivity.

Wang, S. Y.↗
NASA NTRS1978

A study of mass flow in the massive spectroscopic binary HD47129

HD 47129 is a double-lined spectroscopic binary with a period 14.3961 days and a visual magnitude of V = 6.06. Using the Copernicus U2 spectrometer, observations were obtained of the system on eight occasions, starting March 2, 1977. Some results are presented and discussed.

Barlow, M. J.↗
NASA NTRS1977

Asteroid surface compositions from infrared spectroscopic observations - Results and prospects

Advances in IR detector technology, the increased availability of large aperture telescopes, and the techniques of Fourier transform spectroscopy now permit IR (with wavelengths greater than 1 micron) spectroscopic observations of asteroid surfaces. Asteroids already observed include Ceres, Vesta, and Eros. These initial results demonstrate that such studies can contribute new data concerning asteroid compositions. Some of the most diagnostic features of mineral spectra are in the IR spectral region, and for featureless spectra characterized only by slopes the extension of the spectral reflectivity curve into the IR provides tighter constraints on possible mineralogies. A systematic study of additional asteroids should exploit even further this new observational link to problems of meteorite origin and solar system evolution.

Larson, H. P.↗
NASA NTRS1978

Variability in the determination of total atmospheric ozone using remote sensing spectroscopic techniques

A spectroscopic method for remote sensing of total ozone has been applied to airborne observations of solar near-UV radiation in the 3100 to 3600 A wavelength region. The method involves detailed spectral matching of the solar observations with synthetic profiles containing various amounts of ozone absorption. For the 3100-3200 A region, measurements above the tropopause agree well with Broadfoot's (1972) extra-terrestrial solar irradiance values. Discrepancies between the observed spectra and the synthetic profiles at other wavelength regions may be due to distorted ozone absorption coefficients or the presence of other UV-absorbing species in the stratosphere.

Sivjee, G. G.↗
NASA NTRS1978

Clouds and their effects on spectroscopic observations

Data on spectroscopic phase curves of near IR CO2 is reviewed. The composition of the Venusian clouds is discussed. Some recent calculations on the variations in line profiles with different scattering and reflecting models are presented.

Young, L. D. G.↗
NASA NTRS1979

A spectroscopic flare of YZ Canis Minoris

Observations of a spectroscopic flare in YZ Canis Minoris are reported. Emission lines of Mg I, Fe I, and Fe II were found in the spectral region 5090-5350 A. The intensity of the emission lines declined only slightly over a span of 2 hours. No significant radial-velocity difference was found between the emission and absorption lines. The turbulent velocity dispersion was less than 20 km/s. Upper limits of 7500 and 15,000 gauss can be placed on the longitudinal and transverse magnetic fields. The equal intensities of the Mg I b lines imply that the emitting region was optically thick. The intensity ratios did not change with time.

Mochnacki, S. W.↗
NASA NTRS1979

Remote spectroscopic identification of carbonaceous chondrite mineralogies Applications to Ceres and Pallas

High-resolution spectroscopic observations of asteroids Ceres and Pallas have been obtained in the 1.0- to 2.6-micron region. Combined with previous spectral measurements at other wavelengths, this work presents the broadband spectral reflectances of these asteroids over the 0.4- to 3.6-micron region. This extended coverage permits new analyses of the surface mineralogies of these objects. Using laboratory comparison spectra of meteorites and mixtures of terrestrial minerals, the surfaces of Ceres and Pallas are consistent with mixtures of opaques and hydrated silicates, such as are found in types C1 and C2 meteorites. This research emphasizes the importance of the 3-micron spectral region for studying by remote methods the relationship of carbonaceous chondrite mineralogies to asteroid surfaces.

Larson, H. P.↗
NASA NTRS1980

Review of Spectroscopic Data for Measurements of Stratospheric Species

Results and recommendations from a two day workshop are discussed. A review of the current status of experimental and theoretical spectroscopic data on molecules of stratospheric interest is given along with recommendations for additional research. Methods for disseminating new and existing data are also discussed.

Goldman, A.↗
NASA NTRS1979

A spectroscopic study of the optical counterparts of three X-ray bursters

One of the major puzzles in galactic X-ray astronomy is the nature of the galactic bulge sources in general and the X-ray burst sources in particular. The answer to this puzzle is likely to come from studies of the faint blue optical counterparts which have been identified with several of these sources. As part of such a study, some results of a detailed investigation of the spectroscopic properties of the optical counterparts to three X-ray bursters - 4U 1735-44, 4U 1636-53, and MXB 1659-29.

Canizares, C. R.↗
NASA NTRS1980

Search for planets by spectroscopic methods

Spectroscopic means of detecting the motion of a star around a star-planet barycenter are considered. The precision of such an observation, which requires a radial velocity error of not more than 5 m/sec, is discussed in relation to the spectral resolutions of the detectors utilized. The University of Arizona radial velocity spectrometer is then presented, with particular attention given to the location of the absorption cell in a beam of light from an incandescent bulb, high-accuracy wavelength calibration involving the use of a Fabry-Perot interferometer in front of an echelle spectrograph, and future plans for the use of light reflected from a Fabry-Perot etalon to improve transmittance. On the basis of these techniques, it is expected that radial velocities with accuracies sufficient for the detection of extrasolar planets will be obtained.

Serkowski, K.↗