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NASA NTRS1972

Temperatures of Titan and the Galilean satellites at 20 microns.

Determination of the effective temperatures of the satellites by means of broad-band observations made at Mauna Kea in 1971. The temperatures of the Galilean satellites are in fair agreement with observations at shorter wavelengths and with theory. The 20-micron flux of Titan is nearly an order of magnitude lower than expected, suggesting either low surface emissivity or high atmospheric opacity between 18 and 25 micron. Hydrogen could produce the required opacity, but the abundance needed is large.

Morrison, D.↗

NASA NTRS1973

Temperatures of Saturn's rings.

The 20-micron brightness temperatures of the rings were determined using the 224-cm telescope of the Mauna Kea Observatory, and the standard University of Hawaii radiometer with a 17- to 25-micron filter. The observations were made on the nights of Aug. 20 and 21, and Sept. 26 and 27, 1972. The brightness temperatures of the A, B, and C rings are, respectively, 89 plus or minus 3 K, 94 plus or minus 2 K, and 89 plus or minus 4 K. A possible explanation of the relatively high temperature of the C ring is that Saturn has radiation belts and the inner ring is heated by particle bombardment.

Murphy, R. E.↗

NASA NTRS1974

Research in volcanic geology, petrology and planetary science at MIT, 1969 to 1974

The behavior of volcanoes was studied by geologic mapping, petrologic investigations of lava and xenoliths, physical measurements, and theoretical modelling. Field observations were conducted in Alaska (Nunivak Island), Iceland, Hawaii (Mauna Kea), Italy (Etna, Stromboli), and Arizona. The results are discussed and compared with known data for lunar and planetary gelogy. Field methods used for the volcano research are cited and a list is given of all participating scientists and students. Publications and abstracts resulting from the research are also listed.

Mcgetchin, T. R.↗

NASA NTRS1976

Theoretical atmospheric transmission in the mid- and far-infrared at four altitudes

The IR transmission of the terrestrial atmosphere is calculated at four altitudes of interest: Mauna Kea at 4.2 km (2-1000 microns), aircraft at 14 km (5-1000 microns), and balloon at 28 km and 41 km (10-1000 microns). We show both high resolution spectra and broadband averages. The results are intended to serve both as a detailed guide to the interference that is expected from the atmosphere for astronomical spectroscopy and also as an indicator of the relative change in absorption and emission that can be expected at various observing altitudes. One salient result for the spectral region around 100 microns is that the absorption (and emissivity) of the atmosphere drops by a factor of 10 for each increase in altitude of 15 km throughout the aircraft and balloon range; thus balloon-borne astronomical photometry and spectroscopy should both enjoy a considerable advantage over aircraft observations in the 30-300-micron region.

Traub, W. A.↗

NASA NTRS1975

Lunar occultation of Saturn. I - The diameters of Tethys, Dione, Rhea, Titan, and Iapetus

The diameters of Tethys, Dione, Rhea, Titan and Iapetus were determined from observations of their March 30, 1974, lunar occultations, made with the Mauna Kea 224 and 61 cm telescopes. Light curves were obtained simultaneously in four colors, and the difference between the time of occultation at the two telescopes provided a direct measurement of the slope of the lunar limb, found to be small in all cases. The satellite diameters were determined by least-squares fits of model occultation light curves to the data. Titan's diameter must be at least 5800 km, much larger than the currently accepted value of 5000 km, making it the largest satellite in the solar system. This larger diameter implies a low mean density. For the other four satellites arguments are presented in favor of accepting the occultation diameters corresponding to limb darkened disks. Except for Titan, the lunar occultation diameters generally agree with previous diskmeter and radiometric determinations.

Elliot, J. L.↗

NASA NTRS1976

The rotation and morphology of small red spots on Jupiter in 1974

The paper presents observations of the morphology and rotation periods of four long-lived red spots in the equatorial region of Jupiter seen in 1974. Three of the spots were very small (less than 1 arcsec in diameter), but show on the best photographs obtained at the Mauna Kea Observatory station of the NASA-Lowell Planetary Patrol. The spots are not greatly distinguished from other Jovian features on the basis of their rotation or longitudinal drift. Their distinct red color is the main point of interest in light of current ideas as to the origin and nature of the Great Red Spot.

Crump, P. C.↗

NASA NTRS1978

Lunar occultation of Saturn. IV - Astrometric results from observations of the satellites

The method of determining local lunar limb slopes, and the consequent time scale needed for diameter studies, from accurate occultation timings at two nearby telescopes is described. Results for photoelectric observations made at Mauna Kea Observatory during the occultation of Saturn's satellites on March 30, 1974, are discussed. Analysis of all observations of occultations of Saturn's satellites during 1974 indicates possible errors in the ephemerides of Saturn and its satellites.

Dunham, D. W.↗

NASA NTRS1978

Mars - Near-infrared spectral reflectance and compositional implication

Several distinct absorption features, some recognized for the first time, are evident in a newly obtained reflectance spectrum (wavelengths = 0.62-2.6 microns, reciprocal dispersion = 83) of the integral disk of Mars. The effects of Martian atmospheric CO2 have been removed from the spectrum to arrive at a reflectance spectrum that is believed to be due mostly to surface material. Absorptions, at 1.22, 1.55, and 2.05 microns are interpreted to indicate the presence of H2O ice plus high desiccated mineral hydrate, although an H2O ice phase with strongly shifted fundamental frequencies cannot be ruled out. Ferrosilicate and ferric oxide bands near and shortward of 1.0 micron are confirmed. The new observations were made on April 21-23, 1976, universal time, at the 2.24-m telescope on Mauna Kea, Hawaii, using a newly developed infrared spectrometer.

Mccord, T. B.↗

NASA NTRS1979

Infrared images of Jupiter at 5-micrometer wavelength during the Voyager 1 encounter

A coordinated program to observe Jupiter at high spatial resolution in the 5-micrometer wavelength region was undertaken to support Voyager 1 imaging and infrared radiation experiment targeting. Jupiter was observed over a 5-month period from Palomar and Mauna Kea observatories. The frequency of observations allowed the selection of interesting areas for closer Voyager examination and also provided good short-term monitoring of variations in cloud morphology. Significant global changes in the 5-micrometer distribution are seen over this time period.

Terrile, R. J.↗

NASA NTRS1978

Mars - Remote spectral identification of H2O frost and mineral hydrate

A reflectance spectrum (0.62-2.6 microns) of Mars (integral disk) is obtained using a newly developed IR spectrometer at the 2.25 m telescope on Mauna Kea, Hawaii. Details of the instrument, observations, and data reduction are presented. Several distinct absorption features are evident that were apparently caused by H2O, but the positions and intensities of the features are quite unusual. In summary, the regolith is probably not as desiccated and dehydrated as the full disk reflectance spectrum and Viking soil analyses would suggest. The surface materials become desiccated and dehydrated as a result of solar UV effects and because of the relative adsorption and desorption rates during the strong diurnal cycling. There may be significant amounts of H2O at depth, and in the Solis Lacus region the H2O reservoir may extend to within a few centimeters of the surface. The Solis Lacus region may therefore be an important target for future Mars landing or sample return mission.

Huguenin, R. L.↗

NASA NTRS1979

Jupiter's cloud distribution between the Voyager 1 and 2 encounters - Results from 5-micrometer imaging

As part of a continuing effort of ground-based support for Voyager target selection, infrared images in the 5-micrometer wavelength region were acquired in preparation for the Voyager 2 flyby of Jupiter. Observations were made during May 1979 from the Palomar 5-meter telescope and the new 3-meter NASA Infrared Telescope Facility at Mauna Kea and are compared to previous observations. Variations seen in the 5-micrometer flux distribution suggest global patterns of clouding over of some Jovian belts and clearing of others. These data were used to predict the Jovian cloud distribution at the time of the Voyager 2 encounter in order to target the imaging and infrared experiments to areas free of high obscuring clouds.

Terrile, R. J.↗

NASA NTRS1980

Performance of the Zeeman analyzer system of the McDonald Observatory 2.7 meter telescope

The paper describes a multichannel photoelectric Zeeman analyzer at the coude spectrograph of the McDonald 2.7 m reflector. A comparison of Lick and McDonald observations of HD 153882 reveals no significant difference in slopes or zero points of the two magnetic fields indicating that the systematic scale difference of 30-40% is probably instrumental in origin. Observations of the magnetic variable beta Cor Bor revealed a more nearly sinusoidal magnetic curve with less internal scatter than the photographically determined field measures of the Lick and Mauna Kea Zeeman systems. Investigation of periodicity in the secularly varying magnetic minima of beta Cor Bor did not yield evidence of previously noted periodicities other than that expected from the time structure of the data sampling.

Vogt, S. S.↗

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

A photometric investigation of Comet P/Encke

A photometric investigation of Comet P/Encke was undertaken using the 2.2 m telescope and the 0.6 m telescope. The two primary scientific objectives were: (1) measurement of the production rates of OH, CN, C3, and C2 as a function of heliocentric distance; and (2) determination of the comet's rotational period by searching for periodic brightness variations in the inner coma. Synoptic observation in the Canary Islands; Cambridge, Massachusetts; Flagstaff, Arizona; and Mauna Kea were planned for the study of the comet's rotation.

Millis, R. L.↗

NASA NTRS1981

Submillimeter heterodyne detection of interstellar carbon monoxide at 434 micrometers

Laser heterodyne observations of submillimeter emissions from carbon monoxide in the Orion molecular cloud are reported. High frequency and spatial resolution observations were made at the NASA Infrared Telescope Facility on Mauna Kea by the use of an optically pumped laser local oscillator and quasi-optical Schottky diode mixer for heterodyne detection of the J = 6 - 5 rotational transition of CO at 434 microns. Spectral analysis of the 434-micron emission indicates that the emitting gas is optically thin and is at a temperature above 180 K. Results thus demonstrate the potential contributions of ground-based high-resolution submillimeter astronomy to the study of active regions in interstellar molecular clouds.

Fetterman, H. R.↗

NASA NTRS1981

Detection of the J = 6 - 5 transition of carbon monoxide

The J = 6 - 5 rotational transition of carbon monoxide has been detected in emission from the KL 'plateau source' in the Orion molecular cloud. The corrected peak antenna temperature is 100 K, and the FWHM line width is 26 km/sec. These observations were carried out using the 3 m telescope of the NASA IRTF (Infrared Telescope Facility) on Mauna Kea, Hawaii, and constitute the first astronomical data obtained at submillimeter wavelengths with a heterodyne system using a laser local oscillator. The data support the idea that the high-velocity dispersion CO in Orion is optically thin and set a lower limit to its temperature of approximately 180 K.

Goldsmith, P. F.↗

NASA NTRS1981

The spectral reflectance of water-mineral mixtures at low temperatures

Laboratory reflectance spectra in the 0.325-2.5 micron region of bound water, water-mineral mixtures, mineral grains on frost, and frost on minerals are presented. The materials used in this study are montmorillonite, kaolinite, beryl, Mauna Kea red cinder, and black charcoal. It is found that the wavelengths of bound water and bound OH absorptions do not shift appreciably with temperature and can be detected when large amounts of free water ice are present. The decrease in the visible reflectance seen in many planetary reflectance spectra containing strong water ice absorptions can be explained by water-mineral mixtures, mineral grains on frost, or frost on mineral grains. Mineral grains on frost are detectable in very small quantities (fractional areal coverage less than approximately 0.005) depending on the mineral reflectance features, while it takes a thick layer of frost (greater than approximately 1 mm) to mask a mineral below 1.4 microns, again depending on the mineral reflectance. Frost on a very dark surface (albedo about 6%) is easily seen; however, a dark mineral mixed with water could completely mask the water absorptions (shortward of 2.5 microns).

Clark, R. N.↗

NASA NTRS1980

Possible infrared aurorae on Jupiter

Infrared brightenings near the poles of Jupiter at 8 microns were observed in early 1980 by the NASA 3-m Infrared Telescope Facility at Mauna Kea and the Mayall 4-m telescope at the Kitt Peak National Observatory. It is suggested that these brightenings are related to the auroral zones which are determined by the magnetic mapping of the magnetotail onto the atmosphere, rather than by the Io flux tube. They were present in both hemispheres in January, present only in the north in February, and probably absent in the south in March. When visible, they were only seen in the hemisphere where the auroral zone was oriented toward the earth and absent otherwise.

Caldwell, J.↗