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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 NTRS1980

The spectrum of IRC + 10216 from 2.0 to 8.5 microns

Low-resolution spectra of IRC + 10216 have been obtained from 2 to 8.5 microns from NASA's Kuiper Airborne Observatory at an altitude of 12.5 km (41,000 feet). Observations were made during 1976 January and 1977 February. In both sets of data, the spectral flux reaches its maximum between 6.0 and 6.6 microns and the previously reported 3.1-micron feature is observed; no obvious new absorption features have been found. The new data together with other spectral data and measurements of the spatial extent of IRC + 10216 impose conditions that must be met by models of the continuum. Several simple models for 2-8.5 micron radiation are examined. The new continuum data impose a constraint on the size of the grains in the cooler, optically thin part of the object. Earlier photometry has been combined with the present data to yield an improved value of the average period: 644 + or - 17 days. It appears that the variability is irregular and that the minima have been deeper in recent years than they were in 1965-1969.

Witteborn, F. C.↗
NASA NTRS1980

The 20-micron brightness temperature of the unilluminated side of Saturn's rings

Observations of the 20-micron brightness temperature of the unilluminated (north) side of Saturn's rings are presented and discussed in terms of models of B ring heating. Observations centered on the B ring ansae were made at 19.8 microns by the 3-m IR telescope facility on Mauna Kea during a period when the unilluminated side of the rings could be observed from earth. Flux measurements indicate a 20-micron brightness temperature of 56 + or - 1 K, in agreement with that measured at 45 microns by Pioneer 11. Under the assumptions that the emission of the Cassini division is negligible and that the ring brightness temperature is close to the actual temperature, it is shown that the brightness temperature can be accounted for by heating by the disk of Saturn, and is proportional to the sine of the Saturnicentric declination of the sun.

Tokunaga, A. T.↗
NASA NTRS1981

Solar limb brightening at 350 microns

The NASA Infrared Telescope Facility at Mauna Kea was used to observe the intensity profile of the quiet solar limb in the 300-400 micron continuum. A significant resolved brightening of several percent over the outer 60 arcsec of the solar limb in this band is found. However, the magnitude of the brightening is considerably less than that indicated by earlier observations of a total solar eclipse in integrated sun-moon radiation by Beckman, Lesurf, and Ross (1975) in the 1.2 mm continuum. More recent ground-based observations indicate that the magnitude of solar limb brightening at 800 microns and at 1.3 mm is stronger than that at 350 microns. This may be regarded as an indication that the hot material which produces the brightening at the extreme limb, thought to consist in part of chromospheric spicules, is optically thin in the 350 micron continuum.

Lindsey, C.↗
NASA NTRS1981

Images of Jupiter from the Pioneer 10 and Pioneer 11 Infrared Radiometers - A comparison with visible and 5-micron images

The images with geometric control which present Pioneer 10 and 11 Infrared Radiometer data aquired at Jupiter are compared with 5.0-micron and visible images taken in the same time frame. It is found that (1) at 5.0, 20 and 45 microns, the association of dark and light areas with warm and cool areas, respectively, extends to nearly all features observed on the planet; (2) where the normal association of light and dark visible markings with the zone velocity breaks down, the infrared emission seems to follow the visible cloud structure rather than the zonal velocity structure; and (3) exceptions to the general rule involve 20-micron radiation, which reflects conditions in the 0.1-0.3 bar altitude range. A comparison of Pioneer 10 and 11 images suggests that the South Equatorial Belt became brighter at 20 microns, yet remained constant at other wavelengths between the two encounters.

Orton, G. S.↗
NASA NTRS1982

Observations of the 30 micron feature in IRC + 10216

Infrared observations from 30 to 37 microns of IRC+10216 extend the wavelength coverage of the 30-micron feature found in four carbon stars and two planetary nebulae by Forrest, Houck, and McCarthy (1981). The present data confirm the existence of this newly observed feature and determine its shape beyond 30 microns. The determination of the long-wavelength end of the spectral excess depends critically on the assumed underlying continuum. A combined spectrum of the excess is presented and shows the feature to extend to at least 37 microns.

Herter, T.↗
NASA NTRS1982

Observations of the 145.5 micron (OI) emission line in the Orion nebula

A first set of observations of the (OI) 3P to 3P1 (145.5 micron) transition was obtained. The line was observed both in a beam centered on the Trapezium, and in a 7 times wider beam encompassing most of the Orion Nebula. A wide beam map of the region was constructed which shows that most of the emission is confined to the central regions of the nebula. These observations may be compared with reported measurement of the 3P1 to 3P2 (63.2 micron) transition in Orion and are consistent with optically thin emission in the 145.5 micron line and self-adsorbed 63.2 micron emission lines. Mechanisms are discussed for the excitation of neutral oxygen. It is included that much of the observed emission originates in the thin, radio-recombination-line-emitting CII/HI envelope bordering on the HII region.

Stacey, G. J.↗
NASA NTRS1983

A 10 micron survey of star formation in galactic nuclei Virgo spiral galaxies

A survey for 10 micron emission in the nuclei of spiral galaxies in the Virgo cluster is reported. It is found that the nuclei of most luminous spiral galaxies are active 10 micron emitters, and that the luminosity function for the sample can be represented by a simple power law over the entire range sampled. The most luminous sources at 10 microns show only a weak correlation with total optical luminosity, and no correlation with morphological type or location in the cluster. It is argued that the 10 micron flux from the Virgo galaxies arises from active star formation regions. A mean far-IR luminosity of two billion solar luminosities is inferred for the galactic nuclei; the required rate of massive star formation is 0.1 solar masses/yr. The results suggest that the rate of star formation in galactic nuclei has little relationship to the size of the nuclear bulge or the gravitational potential near the center.

Becklin, E. E.↗
NASA NTRS1983

Observations of NGC 7027 from 5.2 to 7.5 microns - The detection of Ni II and additional dust features

NGC 7027 was observed with a multichannel grating spectrometer from 5.2 to 7.5 microns at a spectral resolving power of 120-200. Two new dust emission features are resolved at 5.62 and 6.95 microns, and for the first time the Ni II fine-structure line at 6.64 microns is detected. It is shown that a single molecular dust constituent might account for six of the nine observed dust features between 2 and 14 microns. The strength of the Ni II line indicates either that Ni is not depleted in the neutral gas, or that the line is formed at high density.

Bregman, J. D.↗
NASA NTRS1984

High spatial resolution observations of NGC 7027 with a 10 micron array camera

First observations of a planetary nebula with an infrared charge injection device (CID) array camera are reported. The 10 micron images of NGC 7027 have spatial resolution comparable to that of the highest resolution (less than 2 arcsec) radio aperture-synthesis maps of this source. A much closer correspondence between the mid-infrared and radio appearance of NGC 7027 was found than was known previously, confirming that warm dust is coextensive and well mixed with the gas in the ionized zone. Using maps at three wavelengths, the spatial dependence of the shape of the 8-13 micron spectrum within the nebula is examined. The dip at 9.60 microns is shallowest in regions of enhanced optical extinction (as determined from new images near 4000 and 9000 A obtained with an optical charge coupled device). The 9.60 micron emission is strongest in these same positions. It is shown that the results may be explained not by silicate absorption, but by a combination of emission from two distinct grain populations, one of which is also partly responsible for the variation in extinction across the nebula.

Arens, J. F.↗
NASA NTRS1984

Detection of the Ne III 36 micron forbidden line in the planetary nebula NGC 6543

The first observation of the Ne III 36.02 micron forbidden line in a planetary nebula, NGC 6543, is presented. Since the dominant form of neon in medium-excitation to high-excitation planetary nebulae is Ne III, the abundance of this ion is important in determining the total neon abundance. Use of the 36 micron line for an abundance determination has the advantage of insensitivity to temperature uncertainties. However, current atomic parameters lead to a Ne III abundance in NGC 6543 which is 4.5 times the cosmic neon abundance and 2.6 times the abundance from optical line studies. Although such a high abundance cannot be ruled out immediately, inaccuracies in the infrared level collision strengths are suspected because resonances were neglected in their calculation. The 36 micron line is also useful as a temperature probe when combined with the Ne III 3868-A forbidden line. When compared to Ne III 15.56 micron forbidden line fluxes, a temperature-insensitive density estimate may be obtained. The utility of these line ratios depends upon the actual infrared level collision strengths, which will affect the density range over which they are sensitive.

Shure, M. A.↗
NASA NTRS1984

Absorption features in the 5-8 micron spectra of protostars

High signal-to-noise ratio spectra in the range of 5-8 microns of four sources embedded in molecular clouds are examined using low-temperature laboratory measurements of the 5-8-micron spectra of simple molecules and their mixtures. The absorption, apparent in all four sources, is characterized by highly distinct features ranging from two relatively narrow bands at 6.0 and 6.8 microns in W33A to a broad, shallow, and partially structured feature extending from 5.2 to 7.8 microns in Mon R2-IRS2, BN, and NGC2264. The first feature (W33A) is explained by the OH bending mode in H2O and the CH deformation modes in saturated hydrocarbons; while the second feature (Mon R2-IRS2-type) is explained by the presence of a mixture of saturated and unsaturated hydrocarbons possibly containing strongly electronegative groups.

Tielens, A. G. G. M.↗
NASA NTRS1985

Emission features in the 4-13 micron spectra of the reflection nebulae NGC 7023 and NGC 2023

Spectroscopy from 4 to 13 microns of the visual reflection nebulae NGC 7023 and NGC 2023 has been obtained. These data, together with previous work from 1 to 4 microns, show that the spectra of these sources consist of a relatively flat continuum from 1 to 13 microns and six emission features at 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 microns. The observations rule out equilibrium thermal emission for the features and continuum in reflection nebulae, and point toward a nonequilibrium emission mechanism such as thermal emission from thermally fluctuating small grains or fluorescence from large molecules. The similarity of the emission feature spectra in reflection nebulae to those in other sources suggests a universal emission mechanism, thus implying nonequilibrium emission mechanisms in other sources.

Sellgren, K.↗
NASA NTRS1986

Observations of the 157.7 micron (C II) emission from the galactic H II regions W3 and W51

The 157.7 micron ground-state fine-structure transition of singly ionized carbon was detected from three positions, each in galactic H II region W3 and W51. These findings show that this emission goes beyond the H II regions and the carbon recombination region in each source. In addition these observations establish a lower limit to the luminosity in the 157.7 micron (C II) line of 360 solar luminosity from W3 and 41 solar luminosity from W51. Mechanisms for 157.7 micron-line excitation are discussed, and it is noted that a substantial part of the observed emission originates in the thin carbon recombination line-emitting region which borders on the H II regions and the warm atomic and molecular gas at the surface of neighboring molecular clouds. It is proposed that excitation by electrons present in the diffuse gas surrounding W51 contributes to the extended 157.7 micron (C II) line emission from this region. It was found that the (C II)FIR continuum ratios for W3 and W51 are in agreement with those of other galactic H II regions.

Melnick, G.↗
NASA NTRS1986

Two micron quadrupole line emission of H2 from the Jovian auroral zone

Energetic electron bombardment of the H2 atmosphere in the Jovian auroral zone was studied using a theoretical model for the vibrational-ratational excitation processes. A non-relativistic electron energy deposition program originally developed by Peterson et al. was used. Assuming an incident energy electron spectrum from IUE observations, the calculated intensities of the two micron quadrupole lines from the Jovian auroral zone are shown to be comparable to the intensities of infrared objects in the Orion nebula. Jupiter is fairly dark in the 2 to 2.5 micron spectral range because of strong absorption of cH4 and NH3 vibrational-rotational bands. Consequently, assuming no significant decrease in Jovian auroral activity since the Voyager encounter with Jupiter in 1979, the two micron quadrupole emission of H2 may be observable by ground-based telescope through the two micron atmospheric window.

Kim, S.↗
NASA NTRS1986

Airborne spectrophotometry of P/Halley from 16 to 30 microns

Comet Halley was observed in the 16 to 30 micron region using the Cornell University 7-channel spectrometer (resolution = 0.02) on board the Kuiper Airborne Observatory on 1985 Dec. 14.2. A 30-arcsec aperture (FWHM) was used. Measurements centered on the nuclear condensation micron indicate that if present, the 20 micron silicate feature is very weak, and that a relatively narrow strong feature centered at 28.4 microns possibly exists. However, this feature may be an artifact of incomplete correction for telluric water vapor absorption.

Herter, T.↗
NASA NTRS1986

Airborne spectrophotometry of Comet Halley from 5 to 9 microns

Spectrophotometry from 5 to 9 microns (resolution = 0.02) of comet Halley was obtained from the Kuiper Airborne Observatory on 1985 Dec. 12.1 and 1986 April 8.6 and 10.5 UT. Two spectral features are apparent in all the observations, one from 5.24 to 5.6 microns, and the silicate emission feature which has an onset between 7 and 8 microns. There is no evidence for the 7.5 microns feature observed by the Vega 1 spacecraft; the large difference between the areal coverage viewed from the spacecraft and the airplane may explain the discrepancy. Color temperatures significantly higher than a blackbody indicate that small particles are abundant in the coma. Significant spatial and temporal variations in the spectrum show trends similar to those observed from the ground.

Campins, H.↗
NASA NTRS1988

Development program for 1.93-micron lasers

For the first time lasers operating at 1.93 microns were demonstrated. The lasers were fabricated by Vapor Phase Epitaxial (VPE) growth techniques currently used for the fabrication of high power lasers at 1.3 microns. The structure of these laser diodes consisted of compositionally graded, sulfur-doped InAsP, grown on an InP substrate; a constant-composition n+InAs(0.27)P(0.73) layer, which is the first cladding layer; an In(0.66)Ga(0.34)As layer, which is the active region, and a second InAs(0.27)P(0.73) layer. The devices were oxide-stripe DH lasers (gain-guided only). The best devices had 80 K lasing thresholds in the range of from 80 to 150 mA, and T sub o (below 220 K) in the range of 60 to 90 K. The highest observed temperature of oscillation was 15.5 C. The highest observed power output at 80 K was in the range of 3 to 5 mW. The calculated delta I/delta T was 4.4 A/K. As a part of the materials development, PIN homojunction detectors having the band edge near 1.93 were also fabricated. The best devices (100 micron diameter, mesa structure) exhibited room temperature dark currents in the range of from 20 to 50 nA and had QE at 1.93 microns in the range of 35 to 40 percent. In addition to the device results, the InGaAs-InAsP materials system was extensively investigated and low defect density layers can now be grown allowing for significant device performance improvement.

Longeway, P.↗
NASA NTRS1987

30-micron heterodyne receiver

Advantages and constraints of remote measurements using heterodyne spectroscopy near 30 microns are discussed. The state of the art of wideband HgCdTe photomixers and PbSnSe diode-laser local oscillators being developed for FIR heterodyne receivers is described. The first compact 30-micron heterodyne radiometer was built, and initial results at 28-microns show about 2-percent mixer efficiency for a 500-MHz-bandwidth receiver. Factors limiting receiver performance are discussed, along with the projected sensitivity of new interdigitated-electrode HgCdTe photoconductor mixers being developed for operation up to 200 microns.

Kostiuk, Theodor↗