[en] The purpose of this task is to support asteroid research and the operation of an Asteroid Team within the Earth and Space Sciences Division at the Jet Propulsion Laboratory (JPL). The Asteroid Team carries out original research on asteroids in order to discover, better characterize and define asteroid properties. This information is needed for the planning and design of NASA asteroid flyby and rendezvous missions. The asteroid Team also provides scientific and technical advice to NASA and JPL on asteroid related programs. Work on asteroid classification continued and the discovery of two Earth-approaching M asteroids was published. In the asteroid photometry program researchers obtained N or Q photometry for more than 50 asteroids, including the two M-earth-crossers. Compositional analysis of infrared spectra (0.8 to 2.6 micrometer) of asteroids is continuing. Over the next year the work on asteroid classification and composition will continue with the analysis of the 60 reduced infrared spectra which we now have at hand. The radiometry program will continue with the reduction of the N and Q bandpass data for the 57 asteroids in order to obtain albedos and diameters. This year the emphasis will shift to IRAS follow-up observations; which includes objects not observed by IRAS and objects with poor or peculiar IRAS data. As in previous year, we plan to give top priority to any opportunities for observing near-Earth asteroids and the support (through radiometric lightcurve observations from the IRTF) of any stellar occultations by asteroids for which occultation observation expeditions are fielded. Support of preparing of IRAS data for publication and of D. Matson for his participation in the NASA Planetary Astronomy Management and Operations Working Group will continue

[en] An evaluation is made of observational evidence adduced to date for the various extant models of the Io atmosphere. SO2 and its various photochemical products have been noted to play a major role in the atmosphere; such atomic species as Na and K are present in smaller quantities, and play an important role in the atmosphere's ion chemistry. The vapor pressure equilibrium between condensed SO₂ on the surface and the atmospheric gas is an important factor in the global control of SO₂ gas distribution, but cannot account for the neutral densities at the terminator required for ionospheric models in view of realistic surface temperature distributions

[en] The 'solid-state greenhouse effect' model constituted by the subsurface solar heating of translucent, high-albedo materials is presently applied to the study of planetary surfaces, with attention to frost and ice surfaces of the solar system's outer satellites. Temperature is computed as a function of depth for an illustrative range of thermal variables, and it is discovered that the surfaces and interiors of such bodies can be warmer than otherwise suspected. Mechanisms are identified through which the modest alteration of surface properties can substantially change the solid-state greenhouse and force an interior temperature adjustment. 34 references

[en] This paper reports that the IRAS Asteroid and Comet Survey yield a data base of infrared flux densities for 1811 individual asteroids. Albedos and diameters for these have been derived via a standard thermal model. IRAS sampled a large number of small asteroids and detected many dark asteroids in the outer belt. High-albedo asteroids remain rare. Observations of the brighter asteroids at multiple wavelengths shows the expected range of color temperatures through the main belt

[en] Results of observations with the IUE are reported showing an absorption feature at 280 nm in Europa's reflection spectrum which is strongest on the trailing hemisphere. The feature is identified as a SO₂ absorption band and it is suggested that SO₂ may form when energetic jovian magnetospheric sulphur ions are injected into Europa's water-ice surface. (U.K.)

[en] Albedos and spectral reflectances are essential for classifying asteroids. For example, classes E, M and P are indistinguishable without albedo data. Colorometric data are available for about 1000 asteroids but, prior to IRAS, albedo data was available for only about 200. IRAS broke this bottleneck by providing albedo data on nearly 2000 asteroids. Hence, excepting absolute magnitudes, the albedo and size are now the most common asteroid physical parameters known. In this chapter the authors present the results of analyses of IRAS-derived asteroid albedos, discuss their application to asteroid classification, and mention several studies which might be done to exploit further this data set

No abstract available

[en] Observations made by the Infrared Astronomical Satellite (IRAS) during 1983 constitute the largest, most complete, and least biased of the asteroid surveys to date. A total of 1811 asteroids and 25 comets with known orbits were measured. Thermal flux densities at 12, 25, 60, and 100 microns, as well as (in the case of asteroids) their derived radiometric albedos and diameters have been compiled in the IRAS Asteroid and Comet Survey. Useful low-resolution spectra were obtained for 47 numbered asteroids. There is evidence in the IRAS data base for a large population of asteroids with unknown orbits. The methods of observation are outlined. The survey strategy and the data reduction are discussed. The rationale is given for the various IRAS asteroid and comet data products. Some directions for future research using IRAS data are suggested. 20 refs

[en] The present quantitative modeling of convective, condensational, and sublimational effects on porous ice crust volumes subjected to solar radiation encompasses the effect of such insolation's penetration of visible bandpass-translucent light, but opaque to the IR bandpass. Quasi-steady-state temperatures, H2O mass fluxes, and ice mass-density change rates are computed as functions of time of day and ice depth. When the effects of latent heat and mass transport are included in the model, the enhancement of near-surface temperature due to the solid-state greenhouse effect is substantially diminished. When latent heat, mass transport, and densification effects are considered, however, a significant solid-state greenhouse effect is shown to be compatible with both morphological evidence for high crust strengths and icy shell decoupling from the lithosphere. 21 refs

[en] An analysis of 33 IUE UV spectra of Europa, obtained from 1978 to 1982 for orbital phase angles of 21 to 343 deg, confirms that the Lane et al. (1981) absorption feature, centered at 280 nm, is most clearly revealed when 223-333 deg orbital phase angle spectra are ratioed to those nearest 90 deg. The feature's strength is noted to have persisted over the 5-year period studied, suggesting that no large endogenically or exogenically generated changes in surface sulfur dioxide concentration have occurred. These results further substantiate the Lane et al. hypothesis that the feature is due to the implantation of Io plasma torus-derived sulfur ions on the Europa trailing side's water-ice surface. 31 references