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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 397 records · Page 22
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NASA NTRS1979

The brightness distribution of IRC +10216 at 11 microns

The brightness distribution of IRC +10216 at a wavelength of 11 microns was measured in detail using a spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 minutes. The tapered shape of this component is consistent with a l/r squared dust density dependence. The compact component is unresolved (less than 0.2 minutes in diameter) and represents emission from the central star seen through the circumstellar envelope.

Sutton, E. C.↗
NASA NTRS1978

Martian atmosphere modeling between 0.4 and 3.5 microns - Comparison of theory and experiment

A model of the lower atmosphere of Mars has been constructed that combines aerosol absorption and scattering with a line-by-line analysis of CO2 and H2O in a multilayer radiative transfer program. Aerosol composition previously inferred from the NASA Lear Jet Observatory data was used to measure the optical complex indices of refraction of appropriate Martian analogs from 0.4 to 2.5 microns. The aerosol vertical particle density scale was deduced using the Viking camera observations of the soil and sky intensities between 0.4 and 1.0 microns in comparison with those modeled using a multilayer Mie scattering program. A comparison of observed Mars atmospheric absorptions was made with those obtained using Lorentz, Voigt, and Doppler line profiles in a multilayer model of the CO2 and H2O. The Voigt line profile of CO2 absorption at approximately 4976 kaysers was then combined in a multilayer aerosol model of the Martian atmosphere. An evaluation of the effect on the line shape was made using several aerosol loadings.

Egan, W. G.↗
NASA NTRS1979

Observations of the 63 micron forbidden OI emission line in the Orion and Omega Nebulae

Observations of 63-micron neutral oxygen emission from the Orion and Omega Nebulae are reported which were carried out from the NASA Lear Jet flying at an altitude of approximately 13.7 km. The best estimate for the 3 P 1 - 3 P 2 transition wavelength is shown to be 63.2 microns, and the detected fluxes are found to be extraordinarily high (amounting to approximately 600 suns in M42 at 0.5 kpc and to about 2900 suns in the line in M17 at 2 kpc). Attempts are made to estimate the minimum temperature and other parameters of the emitting region in Orion. It is concluded that conditions not too different from those permitted by some current models appear to provide fluxes that agree in order of magnitude with those observed.

Melnick, G.↗
NASA NTRS1979

Transport of majority and minority carriers in 2-micron-diameter Pt-GaAs Schottky barriers

An experimental study of small area (2-micron diameter) Pt-GaAs Schottky barrier diodes has been made, by using a wafer chip with a matrix of these diodes lying within approximately a minority carrier diffusion length of one another. Using one diode as collector and another as emitter, transistor measurements indicated that the dominant contribution to the current is the majority-carrier thermionic field emission current for large forward-bias voltage of the emitter junction (V-EB no less than about 0.4 V), whereas the smaller forward-bias (V-EB no greater than about 0.4 V) recombination in the space-charge region was most important. The minority carrier injection ratio is measurable only for large forward-bias voltages, decreasing from about 0.02 to 0.00001 as VEB increases from 0.5 to 1.0 V. The minority carrier diffusion length was measured to be about 1.3 microns. These results are of considerable significance for the understanding and optimization of the performance of these devices as classical detectors and mixers.

Chan, E. Y.↗
NASA NTRS1979

The brightness distribution of IRC +10216 at 11 microns

The brightness distribution of IRC +10216 at a wavelength of 11 microns has been measured in detail by using spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 arcsec. The tapered shape of this component is consistent with a dust density dependence on the inverse square of radial distance. The compact component is unresolved (less than 0.2 arcsec in diameter) and represents emission from the central star seen through the circumstellar envelope.

Sutton, E. C.↗
NASA NTRS1979

Detection of Jupiter's ring at 2.2 microns

Reflected sunlight from the Jovian ring discovered by the Voyager spacecraft was detected at 2.2 microns. A chopping secondary photometric system and an indium antimonide photovoltaic apparatus were used in the detection. The search for the ring was conducted at 2.2 microns because at this wavelength scattered radiation from the planetary disk is reduced by the strong molecular absorption features in Jupiter's atmosphere.

Becklin, E. E.↗
NASA NTRS1979

The 63 micron radiation field in the earth's thermosphere and its influence on the atomic hydrogen temperature

The thermal escape of hydrogen from the earth's atmosphere is strongly affected by its temperature at the exobase. It has been suggested recently that the hydrogen temperature might be significantly lower than the thermospheric temperature as a result of a collisional exchange of energy with atomic oxygen. The tendency is to cool the hydrogen since the energy of the excited 3P1 level of oxygen can be lost from the atmosphere via magnetic dipole emission of the micron line (3P2-3P1). A detailed calculation of the net cooling effect as a function of altitude throughout the thermosphere is presented. The calculations have been performed for both day and night conditions and for periods of maximum and minimum solar activity conditions. It is found that its effect on Delta T/T varies from a very small value to a maximum of about 3%. The theoretical framework for describing deviations of the 63 micron emission from local thermodynamic equilibrium is given and it is shown that these effects can cause the emission to be reduced by as much as 40% near 500 km.

Durrance, S. T.↗
NASA NTRS1978

Ultra-low-mass flexible planar solar arrays using 50-micron-thick solar cells

A conceptual design study has been completed which has shown the feasibility of ultra-low-mass planar solar arrays with specific power of 200 watts/kilogram. The beginning of life (BOL) power output of the array designs would be 10 kW at 1 astronomical unit (AU) and a 55C deg operating temperature. Two designs were studied: a retractable rollout design and a non-retractable fold-out. The designs employed a flexible low-mass blanket and low-mass structures. The blanket utilized 2 x 2 cm high-efficiency (13.5% at 28C deg AM0), ultra-thin (50 micron), silicon solar cells protected by thin (75 micron) plastic encapsulants. The structural design utilized the 'V'-stiffened approach which allows a lower mass boom to be used. In conjunction with the conceptual design, modules using the thin cells and plastic encapsulant were designed and fabricated.

Costogue, E. N.↗
NASA NTRS1979

Characteristics of a CW water vapor laser at 118 and 28 microns

The characteristics of a CW water vapor laser operating at 118 and 28 microns are reported. By monitoring the discharge current, helium gas pressure, and water vapor pressure, a criterion for optimum power output has been obtained. Peak powers of 6 and 114 mW are obtained, respectively, for the 118- and 28-micron lines for a 4.5-m discharge tube.

Yasuoka, Y.↗
NASA NTRS1979

Observations of forbidden S III 18.71-micron emission in galactic H II regions

Emission of forbidden S III 18.71-micron radiation has been detected in the Orion Nebula, M17, NGC 2024, and W51, and an upper limit has been set for Sgr A. The line flux from M17 has been mapped with a resolution of 2.7 arcmin. A simple theory for predicting the forbidden S III flux from radio continuum observations is presented and compared with the data. It is found that Orion and M17 are in satisfactory agreement with the observations and that NGC 2024 is consistent with a low-excitation source behind a resonable amount of 18-micron dust extinction. In W51 the low observed flux may be explained either by low S(2+) abundance or, more likely, by dust extinction. In Sgr A attenuation by dust is the most plausible explanation.

Mccarthy, J. F.↗
NASA NTRS1979

Two-micron spectrophotometry of the galaxy NGC 253

A very strong Brackett-gamma hydrogen emission line and the 2.3-micron CO stellar absorption feature have been measured in NGC 253. The presence and strength of the CO feature indicate that late-type giant stars produce most of the 2.2-micron continuum emission, while the rate of ionization implied by strength of the Brackett-gamma line indicates that much, perhaps all, of the luminosity detected at far-infrared wavelengths originates from a large number of OB stars. As compared with the corresponding region of the Galaxy, the number of massive young stars in the central 200 pc of NGC 253 is 30 times greater, but the total mass of stars is roughly the same.

Wynn-Williams, C. G.↗
NASA NTRS1980

Atmospheric solar absorption measurements in the 9-11 micron region using a diode laser heterodyne spectrometer

A tunable diode laser heterodyne radiometer was developed for ground based measurements of atmospheric solar absorption spectra in the 9 to 12 micron spectral range. The performance and operating characteristics of this tunable infrared heterodyne radiometer (TIHR) is discussed along with recently measured heterodyne solar absorption spectra in the 10 to 11 micron spectral region.

Harward, C. N.↗
NASA NTRS1979

The mean intensity of radiation at 2 microns in the solar neighborhood

Consideration is given to the value of the mean intensity at 2 microns in the solar neighborhood, and it is found that it is likely to be a factor of four greater than previously estimated on theoretical grounds. It is noted however, that the estimate does agree with a reasonable extrapolation of the results of the survey of the Galactic plane by the Japanese group. It is concluded that the mean intensity in the solar neighborhood therefore probably peaks somewhat longward of 1 micron, and that this result is important for understanding the temperature of interstellar dust and the intensity of the far infrared background. This means specifically that dark clouds probably emit significantly more far infrared radiation than previously predicted.

Jura, M.↗
NASA NTRS1980

Infrared spectrum of Io, 2.8-5.2 microns

The reflectance spectrum of Io is presented from 2.8 to 5.2 microns demonstrating the full extent of the broad and deep spectral absorption between 3.5 and 4.8 microns. Laboratory spectra of nitrates and carbonates diluted with sulfur do not satisfactorily reproduce the Io spectrum, but new information based on recently discovered volcanic activity on the satellite lead to consideration of other classes of compounds reported by Fanale et al. (1979). It is concluded that the variability of the supply of condensible SO2 gas to the surface of Io, its removal by sublimination, and the temporal variations in the strength of the SO2 band may provide an index of volcanic activity on Io that can be monitored from the earth.

Cruikshank, D. P.↗
NASA NTRS1980

16-30 micron spectroscopy of Titan

Titan has been observed from 16 to 30 micron with a resolution of 1 micron. Earlier broad-band data are consistent with the new measurements, which show that the disk integrated flux is nearly constant over the observed range of wavelengths. Limits on the CH4, H2, and N2 column densities and pressures at the bottom of the upper layer are derived. These indicate that if the atmosphere gas is CH4, an H2-CH4 mix, or N2, the inversion layer must be at pressures less than 30 millibars.

Mccarthy, J. F.↗
NASA NTRS1980

Spectral reflectance and discrimination of plutonic rocks in the 0.45- to 2.45-micron region

Visible and near-infrared field spectral reflectance measurements of plutonic rocks were acquired in the 0.45- to 2.45-micron region with a portable field reflectance spectrometer. These spectra were used to determine spectral signatures for the various rock types and to evaluate the separability of these rocks based on their spectral characteristics. A total of 135 samples were divided into 11 groups based on their mineralogy. These 11 groups approximately correspond to traditional rock classifications and include five granitic groups, three gabbroic groups, and three ultramafic groups. The positions, intensity, and presence of iron, CO3(-2), and Al-OH and Mg-OH absorption bands varied among the 11 groups. Each rock group also had a range of albedos characteristic of the group. Stepwise linear discriminant analysis was performed on the spectral data to determine the separability of the 11 groups. Classification accuracy for 30 equally spaced wavelength bands between 0.45 and 2.45 microns was 78% with 10% serious misclassifications. The same analysis was repeated, limiting the spectral data to the wavelength regions corresponding to the proposed Landsat D thematic mapper scanner.

Blom, R. G.↗
NASA NTRS1980

Io - Are vapor explosions responsible for the 5-micron outbursts

It is proposed that a vapor explosion of a submerged pool of liquid sulfur will remove the crust overlying an area of about 50-km diam. Thermal radiation from the exposed liquid sulfur pool with a surface temperature of 600 K is then presumed to be responsible for the 5-micron outbursts that have been observed. The explosive volcanoes are expected to leave black sulfur calderas, which are, indeed, found on the surface. The 5-micron outburst observed by Sinton (1980), on June 11, 1979 (UT), is identified with a new caldera found on Voyager 2 photographs but which had not been present on Voyager 1 pictures.

Sinton, W. M.↗
NASA NTRS1981

High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion molecular cloud

The pure rotational S(2) line of molecular hydrogen at 12.28 microns was looked for in 44 positions in the Orion moleular cloud with 6 in. beams and 35 km/s spectral resolution; it was detected in 27 positions. Emission was observed over a velocity range of + or - 100 km/s. The lines are approximately symmetric, and have full widths at half maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that seen in the 2 micron hydrogen transitions. However, unexpectedly complex line profiles and point-to-point variations in linear shapes appear, particularly in the region near IRc9.

Beck, S. C.↗