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NASA NTRS1982

Mars - Near-infrared spectral reflectance of surface regions and compositional implications

Both morphological and compositional information are needed to define and characterize surface geologic units on Mars. A description is presented of new, near-infrared spectra (0.65 to 2.50 micrometers) for 11 regions on the Martian surface observed in 1978. The high photometric quality of these data combined with increased near-infrared spectral coverage provide new information about the spectral behavior and, therefore, the composition and physical nature of Martian surface materials. The spectral reflectances were obtained with the aid of a 2.2-m telescope located on Mauna Kea, Hawaii. A cooled (to 77 K) circular variable filter spectrometer with an InSb detector was used to measure alternatively Mars and the standard star Beta Geminorum. Attention is given to general spectral characteristics, the dark region composition, spectral evidence for water, and the 2.3 micrometer absorption.

Mccord, T. B.↗
NASA NTRS1982

Rotational modulation of the chromospheric activity in the young solar-type star, X-1 Orionis

The IUE satellite was used to observe one of the youngest G stars (GO V) for which Duncan (1981) derives an age of 6 x 10 to the 8th power years from the Li abundance. Rotational modulation was looked for in the emission flux in the chromospheric and transition region lines of this star. Variations in the Ca 11 K-lines profile were studied with the CHF telescope at Mauna Kea. Results show that the same modulation of the emission flux of Ca 11 due to stellar rotation is present in the transition region feature of C IV and probably of He II. For other UV lines the modulation is not apparent, due to a more complex surface distribution of the active areas or supergranulation network, or a shorter lifetime of the conditions which give rise to these features, or to the uncertainities in the measured line strengths. The Mg II emission flux is constant to within + or - 3.4% implying a rather uniform distribution of Mg II emission areas. The Ca II emission not only shows a measurable variation in intensity but also variations in detailed line profile shape when observed at high resolution.

Boesgaard, A. M.↗
NASA NTRS1981

InSb heterodyne receivers for submillimeter astronomy

InSb hot electron bolometer mixer receivers have been developed for submillimeter line studies of the interstellar medium up to about 500 GHz. The receivers have been used aboard the NASA Kuiper Airborne Observatory which is transported to about 12,000 km by a C141 aircraft. Data have been obtained on new interstellar lines (such as the ground-state fine structure transition of atomic carbon at 492 GHz) and such molecular transitions as carbon monoxide and water. Other data were obtained at ground level using the 5-cm Hale telescope at Mount Palomar and the NASA Infrared Telescope facility at Mauna Kea, HI. The heterodyne bolometers have reached noise temperatures of less than 400 K at all frequencies to 500 GHz.

Phillips, T. G.↗
NASA NTRS1983

The depletion of calcium in the Rho Ophiuchi cloud

Data on the interstellar Ca II H and K lines toward HD 147889, a star deeply embedded in the rho Ophiuchi dark cloud, were obtained at the Mauna Kea Observatory of the University of Hawaii, using a multi-anode microchannel array (MAMA) detector. An upper limit on the Ca II column density of 1.7 x 10 to the 11th/sq cm was derived, which, together with ionization considerations and an estimated lower limit on the total hydrogen column density, implies that the calcium-to-hydrogen ratio in this line of sight is 0.00000795 or less, relative to the solar value. The logarithmic depletion is up to -5.10, the largest yet measured, and implies that gas-grain interaction in this region has proceeded to a much greater degree than is typical of diffuse clouds.

Snow, T. P.↗
NASA NTRS1982

Galileo Institute for Astronomy (IFA) charge-coupled device (CCD) system

A fully portable self-contained charge-coupled device system has been constructed for shared use with the Galileo Project Imaging Team. The detector currently incorporated in the system is a Texas Instruments 500 x 500 three-phase CCD that has been thinned to operate in the backside illuminated mode. The detector and camera mainframe electronics were provided by the Jet Propulsion Laboratory. The support electronics and control interfaces necessary to operate the mainframe were constructed. The data system, which is built around a DeAnza Visacom VC-5000 Image Processor with an imbedded LSI-11 minicomputer, was also integrated. The capability to do image processing in real-time at the telescope has proved to be extremely valuable. The overall system read noise has been measured at 25 electrons. Full-well capacity is 40,000 electrons. Some results from laboratory tests and initial observing runs at the Mauna Kea 2.2-m telescope are presented.

Hlivak, R. J.↗
NASA NTRS1982

High-resolution spectroscopy with the multi-anode microchannel array detector systems

The results of a series of high-resolution spectroscopic observations undertaken with a linear (1 x 1024)-pixel visible-light Multi-Anode Microchannel Array (MAMA) detector on the Coudespectrograph of the 2.2-meter telescope at the Mauna Kea Observatory and on the vacuum spectrograph of the McMath Solar telescope at the Kitt Peak National Observatory are described. In addition, the two-dimensional MAMA detector systems with (16 x 1024)-pixel, (24 x 1024)-pixel, and (256 x 1024)-pixel formats which are now being readied for use in a series of ground-based, balloon, and sounding-rocket observing programs are briefly described.

Timothy, J. G.↗
NASA NTRS1983

The NH3 spectrum in Saturn's 5 micron window

Spectra of Saturn's 5-micron window were obtained at the Infrared Telescope Facility on Mauna Kea, Hawaii. The spectra have a resolution of 1.2/cm, and some exhibit extremely low amounts of approximately 300-micron ppt telluric H2O. The Saturn spectra show absorptions by the 2nu2 band of NH3. Long-path laboratory comparison spectra of NH3 were acquired and show considerable deviations in intensity from theoretical predictions. The calibration of Saturn's observed NH3 features with the laboratory data gives 2.0 + or - 0.5 m-amagat of NH3 using the 2nu2 Q-branch at 5.32 microns. The R(1) and R(2) lines yield an abundance about 3 times greater. Absorptions outside the range of the Q-branch can be accounted for by solid NH3 of 10-20 microns equivalent path length. The origin of Saturn's 5-micron flux is mostly thermal with some admixture of solar reflected radiation. A depletion of Saturn's NH3 abundance below the solar value is indicated, but confirmation of this conclusion will require a better understanding of the atmospheric penetration depth at 5 microns and more rigorous modeling of the spectral line formation.

Bjoraker, G. L.↗
NASA NTRS1982

Infrared observations of low-mass star formation in Orion - HH objects

The results of a preliminary analysis of IR data on Herbig-Haro objects in the Orion nebula are reported. The observations were made with the high angular resolution IR photometry equipment on the NASA Kuiper Airborne Observatory and the NASA facility on Mauna Kea, HI. Data were taken in the 1-200 microns region with 40, 6, and 8 arcsec resolution. Attention was focused on NGC 1999 (HH1-3) and M78 (HH24-25) and the determination of absolute luminosities of the exciting stars. Measurements were also made of the IR energy distribution in the thermally emitting dust clouds and the point sources. Herbig-Haro objects featured compact and far IR sizes and large visual extinction, in addition to a steeply rising energy distribution up to 50-100 microns, where the luminosity emitted was concentrated.

Harvey, P. M.↗
NASA NTRS1984

Surface compositions in the Aristarchus Region: Implications for regional stratigraphy

Near infrared reflectance spectra for the Aristachus region, obtained using the 2.2m UH telescope at the Mauna Kea Observatory, were reduced and analyzed. The spectra obtained for the central peak, southern floor, southwestern wall, eastern wall, and northwestern wall of Aristachus crater exhibit shallow continuum slopes, relatively strong feldspar bands, pyroxene bands stronger than those typically seen in the spectra of fresh higland features, and pyroxene band centers near l micrometer suggesting the dominance of Ca rich clinopyroxene. The spectrum of the south rim of Aristachus is quite distinct from those of other crater units. The position of Aristrchus on the plateau/mare boundary raises questions concerning compositional variations in crater ejects deposits.

Hawke, H. R.↗
NASA NTRS1984

A cryogenically cooled, multidetector spectrometer for infrared astronomy

A liquid helium-cooled, 24 detector grating spectrometer was developed and used for low resolution astronomical observations in the 5 to 14 micron spectral range. The instrument operated on the 91 cm Kuiper Airborne Observatory, the 3 m IRTF (Mauna Kea), the 3 m Shane telescope Observatory, the 3 m Shane telescope (Lick Observatory), and the 152 cm NASA and University of Arizona telescope. The detectors are discrete Si:Bi photoconductors with individual metal oxide semiconductor field effect transistor preamplifiers operating at 4 K. The system uses a liquid helium-cooled slit, order-sorter filter, collimator mirror, grating, and camera mirror arranged in a Czerny-Turner configuration with a cold stop added between the collimator mirror and the grating. The distances between components are chosen so that the collimator mirror images the secondary mirror of the telescope onto the cold stop, thus providing a very effective baffle. Scattered radiation is effectively reduced by using liquid helium-cooled, black baffles to divide the spectrometer into three separate compartments. The system noise-equivalent flux density, when used on the 152 cm telescope from 8 to 13 microns with a resolving power of 50, is 4.4 x 10 to the minus 17th power W/sq cm micron square root of Hz. The main applications are for measuring continuum radiation levels and solid state emission and absorption features in regions of star and planet formation.

Witteborn, F. C.↗
NASA NTRS1983

High-resolution observations of the 6815-A band of methane in the major planets

High-resolution (0.1-A) spectra of the 6815-A band of methane are presented for Jupiter, Saturn, Uranus, and Neptune. Spectra for Uranus, Neptune, and the equatorial region of Saturn were acquired with the SPIFI (Smith, Hicks, and Born (1978) at the 2.2-m telescope of the Mauna-Kea Observatory during May and June 1980. Additional spectra were obtained for Jupiter and the northern temperate and polar regions of Saturn in December 1980 and January 1981 from Kitt Peak National Obsevatory's McMath Solar Telescope. The spectra show a dichotomy in strength of methane absorption between Jupiter-Saturn and Uranus-Neptune. A simple model analysis, based on homogeneous scattering models, is unable to resolve whether this dichotomy is due to an actual increase in the methane mixing ratio with solar distance or to the temperature dependence of line strengths and absorption pathlengths in these atmospheres. If the rotational quantum number for the prominent 6818.9-A feature is J less than 4, then significant aerosol extinction must exist within the visibly accessible portion of Uranus' atmosphere for the methane mixing ratio to be greater than the solar value.

Baines, K. H.↗
NASA NTRS1984

A measurement of stratospheric HO2 by ground-based millimeter-wave spectroscopy

Stratospheric perhydroxyl (HO2) was measured by using a sensitive mm-wave receiver to obtain spectroscopic line profiles of three rotational emission lines in the vicinity of 265.8 GHz. The observations were carried out over four days in September-October 1982 at Mauna Kea, Hawaii and yield good agreement with the column density and vertical distribution predicted above 35 km by three representative two-dimensional photochemical models employing JPL 82-57 reaction rates and chemistry. Contrasts between current theoretical predictions and previous observations by Anderson et al. (1981) are pointed out for HO2 in the 28 to 37-km range, along with the difficulty of joining the latter with the present measurements through a monotonically varying vertical profile for HO2. A possible explanation involving strong temporal and spatial variation in stratospheric water vapor content is suggested.

De Zafra, R. L.↗
NASA NTRS1984

A search for the 10-micron silicate feature in periodic Comet Grigg-Skjellerup

A 10-micron spectrum of periodic Comet Grigg-Skjellerup was obtained on 22 June 1982 with the UCL array spectrometer at the United Kingdom Infrared Telescope, Mauna Kea. No emission feature is obvious in the spectrum. The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent (3sigma) warm, 'dirty' silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns.

Hanner, M.↗
NASA NTRS1982

The excitation and distribution of CO (J = 6-5) emission in the Orion Nebula

Observations of the 691-GHz (J = 6-5) transition of CO in the BN/KL region of Orion obtained in February 1981, at the IR Telescope Facility at Mauna Kea are reported. The system employs a heterodyne receiver with an overall noise temperature of 3900 K DSB at 432 microns, 64 5-MHz IF-filter-bank channels, and a chopping secondary with 120-arcsec excursion, and has 35-arcsec resolution. Sample data are presented graphically and analyzed using a rate equation and a kinetic model. A 35 x 45-arcsec core with hot broad plateau emission (antenna temperature 180 + or - 36 K) surrounded by an area of strong narrow-line 120-K emission is found. It is suggested that the plateau emission originates in a wide thin sheet after a shock wave, with H2 density at least 10 to the 6th/cu cm and gas kinetic temperature greater than 500 K.

Buhl, D.↗
NASA NTRS1983

The grains and gas in Comet Bowell 1980b

The importance of coordinating different types of observations of a comet is illustrated in terms of spectral data on Comet Bowell. Photometric data in 1980 indicated that OH emissions were occurring when the comet was still more than 4 AU from the sun. Further measurements were arranged with the IUE satellite, the photoelectric scanner at Cerro Tololo and the IR telescope on Mauna Kea. Several sizes of diaphragms were used in order to estimate variations with respect to aperture. Calculations were made to quantify the wavelengths observed as a function of the grains' cross-sections. The OH emission was confirmed by the spectrographic and photometric data. It is suggested that sufficient dark materials are present on the cometary surface to have enhanced the absorption of solar radiation to levels sufficient for heating and dissociating surface ice particles.

Dwek, E.↗
NASA NTRS1984

Far Infrared and Submillimeter Observations of the Giant Planets

Far infrared measurements of the effective temperatures of Jupiter, Saturn, Uranus and Neptune were made. The measurements presented here cover the range from 35-1000 micrometers in relatively narrow bands. The observations at lambda 350 micrometers were made at the 3m NASA Infrared Telescope Facility (IRTF) of the Mauna Kea Observatory; those at lambda 350 micrometer were made on the Kuiper Airborne Observatory (KAO). All observations of Saturn were made when the ring inclination to Earth was 1.7 deg assuring an unambiguous measurement of the flux from the disk itself. Mars was used as the calibration reference. The results represent a consistent set of calibration standards. In these measurements, it is assumed that sub b(lambda = 350 micrometers) = T sub (lambda 350 micrometers). Measurements have been made of roughly 50% of the total flux emitted by Jupiter, 65% by Saturn, and 92% by Uranus and Neptune. These measurements therefore permit a considerable reduction in the uncertainties associated with the bolometric thermal outputs of the planets. The effective temperatures (T sub e) and the ratios of emitted to absorbed solar radiation were calculated.

Loewenstein, R. F.↗
NASA NTRS1984

Instrumentation for Submillimeter Polarimetry

During the last two years three instruments were built and operated for detection of polarization in the submillimeter to millimeter wavelength bands. In principle, simply rotating a polarizing grid in front of the detector would be sufficient to determine the state of linear polarization. In practice severe systematic problems are found with this approach. Everything in the light path has potential for inducing polarization. The telescope, apertures in the lightpath, and the Winston light collectors all introduce systematic errors. (The polarization/depolarization induced by these devices is due to diffraction and the finite conductivity of the metals used). Two of the polarimeters are for use on the KAO; the third is for the IRTF on Mauna Kea. The airplane polarimeters, M1 and M2, were specifically designed to minimize the systematic errors. The ground based polarimeter uses our f/35 photometer with an external polarizing grid as the analyzer. With all three instruments the key to success is the data collector and analysis scheme.

Dragovan, M.↗
NASA NTRS1985

First Direct Detection of Clay Minerals on Mars

Magnesian clays or clay-type minerals were conclusively detected in the martian regolith. Near-IR spectral observations of Mars using the Mauna Kea 2.2-m telescope show weak but definite absorption bands near microns. The absorption band positions and widths match those produced by combined OH stretch and Mg-OH lattice modes and are diagnostic of minerals with structural OH such as clays and amphiboles. Likely candidate minerals include serpentine, talc, hectorite, and sponite. There is no spectral evidence for aluminous hydroxylated minerals. No distinct band occurs at 2.55 microns, as would be expected if carbonates were responsible for the 2.35 micron absorption. High-albedo regions such as Elysium and Utopia have the strongest bands near 2.35 microns, as would be expected for heavily weathered soils. Low-albedo regions such as Iapygia show weaker but distinct bands, consistent with moderate coatings, streaks, and splotches of bright weathered material. In all areas observed, the 2.35-micron absorption is at least three times weaker than would be expected if well-crystallized clay minerals made up the bulk of bright soils on Mars.

Singer, R. B.↗