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Knowledge of the hydrated mineral inventory on the asteroids is important for deducing the origin of Earth's water, interpreting the meteorite record, and unraveling the processes occurring during the earliest times in solar system history. Reflectance spectroscopy shows absorption features in both the 0.6-0.8 and 2.5-3.5-micron regions, which are diagnostic of or associated with hydrated minerals. Observations in those regions show that hydrated minerals are common in the mid-asteroid belt, and can be found in unexpected spectral groupings as well. Asteroid groups formerly associated with mineralogies assumed to have high-temperature formation, such as M- and E-class steroids, have been observed to have hydration features in their reflectance spectra. Some asteroids have apparently been heated to several hundred degrees Celsius, enough to destroy some fraction of their phyllosilicates. Others have rotational variation suggesting that heating was uneven. We summarize this work, and present the astronomical evidence for water- and Hydroxl-bearing minerals on asteroids.

We present spectroscopic observations of 16 asteroids from 1.9-3.6 microns collected from the United Kingdom Infrared Telescope (UKIRT) from 1996-2000. Of these 16 asteroids, 11 show some evidence of a 3 microns hydrated mineral absorption feature greater than 2(sigma) at 2.9 microns. Using relations first recognized for carbonaceous chondrite powders by Miyamoto and Zolensky and Sato et al., we have determined the hydrogen to silicon ratio for these asteroids and calculated their equivalent water contents, assuming all the hydrogen was in water. The asteroids split into 2 groups, roughly defined as equivalent water contents approx. greater than 7% (8 asteroids, all with 3 microns band depths approx. greater than 20%) and approx. greater than 3% for the remaining 8 asteroids. This latter group includes some asteroids for which a weak but statistically significant 3 microns band of non-zero depth exists. The G-class asteroids in the survey have higher water contents, consistent with CM chondrites. This strengthens the connection between CM chondrites and G asteroids that was proposed by Burbine. We find that the 0.7 microns and 3 microns band depths are correlated for the population of target objects.

We present spectroscopic observations of 16 asteroids from 1.9-3.6 microns, collected from the United Kingdom Infrared Telescope (UKIRT) from 1996-2000. Of these 16 asteroids, 11 show some evidence of a 3-micron hydrated mineral absorption feature greater than 2 sigma at 2.9 microns. Using relations first recognized for carbonaceous chondrite powders by Miyamoto and Zolensky (1994) and Sato et al. (1997), we have determined the hydrogen/silicon ratio for these asteroids and calculated their equivalent water contents, assuming all the hydrogen was in water. The asteroids split into two groups, roughly defined as equivalent water contents of greater than approx. 7% (eight asteroids) and less than approx. 3 % (the remaining eight asteroids). This latter group includes some asteroids for which there is a small but statistically significant 3-micron band of non-zero depth. The G-class asteroids in the survey have higher water contents, consistent with CM chondrites. This strengthens the connection between CM chondrites and G asteroids that was proposed by Burbine (1998). We find that the 0.7-micron and 3-micron band depths are correlated for the population of target objects.

Knowledge of the hydrated mineral inventory on the asteroids is important for deducing the origin of Earth's water, interpreting the meteorite record, and unraveling the processes occurring during the earliest times in solar system history. Reflectance spectroscopy shows absorption features in both the 0.6-0.8 and 2.5-3.5 micrometers regions, which are diagnostic of or associated with hydrated minerals. Observations in those regions show that hydrated minerals are common in the mid-asteroid belt, and can be found in unexpected spectral groupings, as well. Asteroid groups formerly associated with mineralogies assumed to have high temperature formation, such as M- and E-class asteroids, have been observed to have hydration features in their reflectance spectra. Some asteroids have apparently been heated to several hundred degrees Celsius, enough to destroy some fraction of their phyllosilicates. Others have rotational variation suggesting that heating was uneven. We summarize this work, and present the astronomical evidence for water- and hydroxyl-bearing minerals on asteroids.

We report the first multi-filter set of absolutely-calibrated near-infrared images of Uranus, its rings, and three major satellites - Titania, Ariel, and Miranda.

Because stars emit very small portions of their outputs in the far infrared, using them as calibrators requires precise measurement and correction for filter leaks at shorter wavelengths. Therefore, it is common to base far infrared calibrations on planetary objects such as asteriods. However, asteroids are complex geological bodies whose thermal properties depend on their evolutionary histories as well as on their gross parameters such as mass and composition, making them difficult to model as calibrators. We propose a new method for measuring filter leaks that can be carried out using the end-to-end detector system and therefore allows reliable use of stellar calibrators. We illustrate this method by showing that the Infrared Astronomy Satellite (IRAS) 100 micrometers (Band 4) filters had a short wavelength leak of 14.3% +/- 3.6% on stars similar to alpha Boo, but that there is no detectable leak in the 60 micrometers (Band 3) filters. We derive a calibration for Band 4 from stellar colors in a way that is closely analogous to the calibrations of Bands 1, 2, and 3. With correction for the leak, the stellar-based calibration is virtually identical to the original calibration based on asteroids; this result requires that the spectra of the asteriods for the original calibration differ from greybody behavior between 60 and 100 micrometers by about 10%.

The 52-color asteroid survey (Bell et al., 1988) together with the 8-color asteroid survey (Zellner et al., 1985) provide a data set of asteroid spectra spanning 0.3-2.5 micrometers. An artificial neural network clusters these asteroid spectra based on their similarity to each other. We have also trained the neural network with a categorization learning output layer in a supervised mode to associate the established clusters with taxonomic classes. Results of our classification agree with Tholen's classification based on the 8-color data alone. When extending the spectral range using the 52-color survey data, we find that some modification of the Tholen classes is indicated to produce a cleaner, self-consistent set of taxonomic classes. After supervised training using our modified classes, the network correctly classifies both the training examples, and additional spectra into the correct class with an average of 90% accuracy. Our classification supports the separation of the K class from the S class, as suggested by Bell et al. (1987), based on the near-infrared spectrum. We define two end-member subclasses which seem to have compositional significance within the S class: the So class, which is olivine-rich and red, and the Sp class, which is pyroxene-rich and less red. The remaining S-class asteroids have intermediate compositions of both olivine and pyroxene and moderately red continua. The network clustering suggests some additional structure within the E-, M-, and P-class asteroids, even in the absence of albedo information, which is the only discriminant between these in the Tholen classification. New relationships are seen between the C class and related G, B, and F classes. However, in both cases, the number of spectra is too small to interpret or determine the significance of these separations.

The close Earth approach of the Apollo asteroid 4179 Toutatis during the winter of 1992-1993 provided a unique opportunity for detailed ground-based observations of a near earth asteroid (NEA). Because of their relatively small size NEA's are usually far too faint to be observable by most ground-based instruments. This opposition by Toutatis was, however, exceptionally favorable. Toutatis approached within 0.03 AU of Earth and was as bright as 11th visual magnitude. This made the object observable in a wide variety of wavelengths including radar, thermal IR, near IR, and visual.

The goal is to determine whether any of the near-earth asteroids contain water-bearing phyllosilicate (clay) minerals. If these minerals are present, they would provide a readily available source of water for propellant generation and use in life support systems. Telescopic detection of water on the near-earth asteroids is complicated because thermal emission from the asteroid itself masks the diagnostic absorption features for objects this close to the sun. Sophisticated thermal models are necessary to determine whether the absorption features are present. This year, development of these models was continued and more telescopic data to test the models was obtained.

Observed geology, photometry, and geophysical data are used to examine various processes and properties that may have contributed to Maranda's evolution. Global tectonics and surface flow features constrain the possible heating mechanisms and materials. Statistics on impact craters and comparisons with other satellites suggest that the impactor-source population evolved through time and that ejecta mantling has resurfaced significant portions of the surface. It is proposed that the coronae, which are unique to Miranda, were formed by relaxation of topographic highs, by lithospheric stress driven by intensity anomalies in the asthenosphere, or by diapirs either breeching the surface or feeding large-scale volcanic flooding through preexisting crack structure.

Infrared photometry is reported for 22 Aten, Apollo, and Amor asteroids. Thermal models are used to derive the corresponding radiometric albedos and diameters. Several of these asteroids appear to have surfaces of relatively high thermal inertia due to the exposure of bare rock or a coarse regolith. The Apollo asteroid 3103, 1982 BB, is recognized as class E. The Jupiter-crossing Amor asteroid 3552, 1983 SA, is confirmed as class D, but low albedos remain rare for near-earth asteroids.

Asteroids appear in light of telescopic and meteority studies to be the most accessible repositories of early solar system history available. In the cooler regions of the outer asteroid belt, apparently unaffected by severe heating, the C, P, and D populations appear to harbor significant inventories of volatiles; the larger primordial belt population may have had an even greater percentage of volatile-rich, low-albedo asteroids, constituting a potent asteroid for veneering early terrestrial planet atmospheres. The volatile-rich asteroids contain carbon, structurally bound and adsorbed water, as well as remnants of interstellar material predating the solar system.

Measurement strategies are now being planned for using the Visual and Infrared Mapping Spectrometer (VIMS) to observe the asteroid Hestia, and the nucleus, and the gas and dust in the coma of comet P/Tempel 2 as part of the Comet Rendezvous Asteroid Flyby (CRAF) mission. The spectral range of VIMS will cover wavelengths from 0.35 to 5.2 micrometers, with a spectral resolution of 11 nm from 0.35 to 2.4 micrometers and of 22 nm from 2.4 to 5.2 micrometers. The instantaneous field of view (IFOV) provided by the foreoptics is 0.5 milliradians, and the current design of the instrument provides for a scanning secondary mirror which will scan a swath of length 72 IFOVs. The CRAF high resolution scan platform motion will permit slewing VIMS in a direction perpendicular to the swath. This enables the building of a two dimensional image in any or all wavelength channels. Important measurements of the dust coma will include the onset of early coma activity, the mapping of gas and dust jets and correlations with active nucleus areas, observations of the dust coma from various scattering phase angles, coverage of the low wavelength portion of the thermal radiation, and the 3.4 micrometer hydrocarbon emission. A description of the VIMS instrument is presented.

The occultation of AG+40 deg 0783 by 324 Bamberga on 8 December 1987 was observed at 13 sites in the United States, Japan, and China. At four sites the event was observed photoelectrically; the other observations were visual. A least-squares fit of a circular limb profile to the data gives a diameter of 227.6 + or - 1.9 km. However, this solution is inconsistent with a negative visual observation near the northern edge of the ground track. The inconsistency cannot be removed by assuming an elliptical profile. The data suggest that Bamberga, despite its low-amplitude lightcurve, may depart significantly from a spherical or ellipsoidal shape. The asteroid also appears to be at least 10 percent smaller than indicated by infrared radiometry.

A positive correlation was found between the strength of the 3-micron water feature and the strength of the absorption feature shortward of 0.4 microns. This is similar to what is seen in laboratory spectra of carbonaceous chondrites whose silicate compositions range from hydrated phyllosilicates to anhydrous olivine. Features were found in the IRAS images that appear to be related to solar system objects. Analysis of the data has yielded narrow trails of dust coincident with the orbits of comets Temple 2, Encke, and Gunn. Dust is found both ahead and behind comet orbital positions due to low-velocity ejection of large particles during perihelion passage. The occultation diameters of Ceres and Pallas were used to improve the standard thermal model used in the reduction of thermal IR observations of asteroids.

Analysis of data from the Infrared Astronomical Satellite has yielded evidence for narrow trails of dust coincident with the orbits of periodic comets Tempel 2, Encke, and Gunn. Dust was found both ahead of and behind the orbital positions of these comets. This dust was produced by the low-velocity ejection of large particles during perihelion passage. More than 100 additional dust trails are suggested by the data, almost all near the detection limits of the satellite. Many of these dust trails may be derived from previously unobserved comets.

The occultation of BD+8 degrees 471 by Ceres on 13 November 1984 was observed photoelectrically at 13 sites in Mexico, Florida, and the Caribbean. These observations indicate that Ceres is an oblate spheroid having an equatorial radius of 479.6 + or - 2.4 km and a polar radius of 453.4 + or - 4.5 km. The mean density of this minor planet is 2.7 gm/cubic cm + or - 5%, and its visual geometric albedo is 0.070. While the surface appears globally to be in hydrostatic equilibrium, firm evidence of real limb irregularities is seen in the data.

The Infrared Astronomical Satellite (IRAS) scanned the celestial sphere during 1983 through bandpasses centered at wavelengths of 12, 25, 60 and 100 microns. In addition to sources fixed on the sky, many moving objects were observed. This data set is the largest and least biased survey of asteroids and comets ever conducted. Included are main belt asteroids, Mars-crossers, earth-approachers, and Trojans. Measurements for the known asteroids have been reduced and organized into a number of data products which are available to researchers. The data for 'new' asteroids are being processed.

Improved spectrophotometry of Triton at 2.16 microns was obtained with the MMT infrared photometer at a resolution of 1.0 percent. The observations do not reveal an absorption feature due to liquid nitrogen. Three explanations are consistent with this finding: (1) there is liquid nitrogen on the surface but it is not distributed uniformly; (2) the feature varies with time, e.g., it is sometimes obscured by cloud cover; and (3) the feature might be relatively broad.

Narrowband spectrophotometry between 2.3 and 3.5 micrometers is presented for 14 main-belt C asteroids greater than 100 km in diameter. Absorption features at 3 micrometers due to water of hydration are present in the spectra of nine of the asteroids, with intensities ranging from 6 to 23 percent. The other five asteroids have no such absorption greater than 2 percent in intensity. The present C-asteroid population may be fragments of larger parent bodies with anhydrous C3-like cores and hydrated C1I- or C2M-like mantles.

The first successful ground-based observations of any asteroid at submillimeter wavelengths are reported. Observations of the asteroid 10 Hygiea at 370 and 770 micrometers are combined with observations in the near and thermal infrared (2.2, 10.6, and 21 micrometers) to study the thermal properties of Hygiea's regolith. The 'standard' (nonrotating) thermal model is consistent with the entire data set, although a rotating thermophysical model with a 'lunarlike' thermal inertia cannot be ruled out.

Spectrophotometry is presented in the 2.7-4.1 micrometer spectral region for icy satellites of Saturn (Tethys, Dione, Rhea, Iapetus and Hyperion) and Jupiter (Europa, Ganymede and Callisto). The 3.6-micrometer reflectance peak characteristic of fine-grained water ice is observed prominently on the satellites of Saturn, faintly on the leading side of Europa, and not at all on Ganymede, Callisto or the dark side of Iapetus. The spectral reflectances of these icy satellites may be affected by their equilibrium surface temperatures and magnetospheric effects.

Near-simultaneous measurements in 11 wavebands between 1 micron and 2 mm of a sample of 13 'blazars' are presented. These measurements represent the first comprehensive attempt to determine the infrared-to-millimeter-wave properties of this class of object, which emit the bulk of their luminosity in the far-infrared region. Most of the sources have very flat millimeter/submillimeter spectra up to the highest observed frequency. However, 3C 279 and 3C 446 show evidence of turnovers in their submillimeter spectra. The 1-4 micron spectra can be characterized by simple power laws, all steeper than -0.9; several sources, however, show evidence of spectral beaks in the 10-20 micron region, suggestive of energy losses. It is shown that the spectral properties are consistent with synchrotron emission from relativistic jets aligned close to the line of sight and the observations are discussed in relation to such models.

Observations of eight Neptune occultations from six sites in the southwestern Pacific on June 15, 1983. The data were used to search for evidence of rings around Neptune down to a distance of 0.03 Neptune radii from the planetary surface, but the results were negative. An astrometric analysis of the timings yielded solution for the equatorial radius a(0) of Neptune at 1 microbar pressure and the oblatness e at this level. The results are: a(0) = 25,295 + or - 50 km; e = 0.022 + or - 0.004, from which a value for a(1) (equatorial radius at 1 bar pressure) of 24,830 + or - 100 km; and a rotation period of P = 15 h (+3, -2 h) is derived. These results are based on a recent determination of Neptune's pole position and mass quadruple moment, and are consistent with the hypothesis that Neptune and Uranus have homologous mass distributions, although the constraint on interior structure is a weak one. If the probable uncertainty of the pole position is taken into account, error bars on e and derived quantities should be increased by about 50 percent. The present determinations of Neptune atmospheric temperatures at 1 microbar are consistent with earlier results and when combined with all previous data give an average value of 156 + or - 10 K. There is only slight evidence for any latitude dependence in the temperatures. Profiles with a high signal-to-noise ratio suggest the possible presence of an absorbing layer at altitudes higher than the 1-microbar level.

Five-color (wavelength = 0.36-0.85 microns) and thermal infrared (wavelength = 22.5 microns) photometric observations of the unusual asteroid 2060 Chiron were made. Between 0.36 and 0.85 microns, Chiron's reflectance spectrum is similar to those of C-class asteroids as well as Saturn's satellite Phoebe. However, the thermal IR measurements imply an albedo greater than 0.05 (i.e., a diameter of less than 250 km at the 2-sigma level) that is probably higher than those of C-class asteroids or Phoebe.

Spacecraft and ground-based optical, radio and spectrophotometric data on the Saturn satellites are reviewed for clues as to the composition and microstructures of the objects. Minas, Enceladus, Tethys, Dione and Rhea have similar photometric phase integrals, with some diversion exhibited by Rhea. Hyperion is nearly the same color as Iapetus, which displays an overall hemispherical optical asymmetry. Water ice has been observed on many of the satellites and on small, cratered objects within the rings. The frost layers are more extensive than those detected on Jovian satellites. Titan has a methane atmosphere. Finally, Phoebe is suspected of being a captured, asteroidal body.

High resolution spectroscopic observations of asteroid 2 Pallas from 1.7-3.5 microns are reported. These data are combined with previous measurements from 0.4-1.7 microns to interpret Pallas' surface mineralogy. Evidence is found for low-Fe(2+) hydrated silicates, opaque components, and low Fe(2+) anhydrous silicates. This assemblage is very similar to carbonaceous chondrite matrix material such as is found in type CI and CM meteorites, but it has been subjected to substantial aqueous alteration and there is a major extraneous anhydrous silicate component. This composition is compared to that of asteroid 1 Ceres. Although there are substantial differences in their broad band spectral reflectances it appears that both asteroids are genetically related to know carbonaceous chondrites.

A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.

Infrared observations of Comet Bowell represent the first search for frost signatures in a comet beyond 2 AU from the sun. Broad- and narrowband photometry has been obtained as well as CVF spectrophotometry of this comet and there is no evidence for absorption features in the spectral area between 1.25 and 2.3 microns. Models of the coma have been generated which constrain the volatile content of the grains an; are in agreement with the observed albedo. The darkness of the coma particles at large heliocentric distances indicates a low albedo nucleus as well. Brightness variations during the observing period seem to indicate an active nucleus at 4.5 AU from the sun.

J, H, K, L and L-prime broadband and 2.8-3.8 micron narrowband photometric observations have been made of the dark side of Iapetus with circularly variable filter techniques. A 3-micron absorption feature is found which is too deep to be a residual water frost feature from the bright material around the poles. In light of laboratory simulations showing that the dark material must have a strong 3-cm absorption, it is suggested that the material may be a hydrated silicate mixed with a small amount of water frost.

A high-resolution Fourier spectrum (1.7-3.5 microns) and medium-resolution spectrophotometry (2.7-4.2 microns) were obtained for Asteroid 1 Ceres. The presence of the 3-micron absorption feature due to water of hydration was confirmed. The 3-micron feature is compared with the 3-micron bands due to water of hydration in clays and salts. It is concluded that the spectrum of Ceres shows a strong absorption at 2.7-2.8 microns due to structural OH groups in clay minerals. The dominant minerals on the surface of Ceres are therefore hydrated clay minerals structurally similar to terrestrial montmorillonites. There is also a narrow absorption feature at 3.1 microns which is attributable to a very small amount of water ice on Ceres. This is the first evidence for ice on the surface of an asteroid.

Photometry at 3.5 microns was taken with the Infrared Telescope Facility of the Multiple Mirror Telescope to obtain an improved IR spectrum of Triton. The observations show features that are not in detailed agreeement with previous identifications of methane or methane frost, although the general spectral behavior leading to such identifications has been confirmed. It is believed that a combination of surface and atmospheric absorptions may resolve some discrepancies; for instance, many hydrated minerals and frosts which are dark between 3.0 and 4.0 microns may combine with a carbon monoxide atmosphere to yield the data in question.

Infrared thermal emission measurements are reported of 1862 Apollo, which is the type example of an earth-crossing asteroid. A geometric albedo of 0.21 plus or minus 0.02 is derived which is within the albedo range of the S class of asteroids. The effective diameter was observed to vary with rotation from 1.2 plus or minus 0.1 to 1.5 plus or minus 0.1 km.

The spectral reflectances of primary components of the carbonaceous chondrite matrix materials (CCMM) and their secondary alteration products are compared with new observations of low-albedo asteroids. It is shown that the spectral differences between C-type asteroids and carbonaceous chondrites are consistent with differing degrees of aqueous alteration of CCMM.

Medium-resolution infrared (1-2.5 microns; Delta-lambda/lambda = 0.05) photometry of Triton, Titania, and Hyperion and medium-resolution (1.5-2.4 microns; Delta-lambda/lambda not greater than 0.01) spectroscopy of Triton are presented. Hyperion and Titania have spectra roughly similar to the laboratory spectrum of water frost, while the spectrum of Triton is inconsistent with the spectra of frosts likely to be major surface constituents.

The occultation of SAO 115946 by Juno on 11 December 1979 was observed from two sites in southern California with portable two-color, high-speed photometers. A composite light curve was constructed from the data by suitable scaling of individual observations, using an astrometric solution for the location of the contact points on Juno's limb. The preliminary astrometric solution used here has a semiminor axis of 118 km and a semimajor axis of 145 km at position angle 75.5 deg. The composite light curve is compatible with a stellar radius of (1.6 + or - 0.8) x 10 to the -4th arcsec, consistent with the radius estimated from the color and visual magnitude. There is no evidence for any companions to SAO 115946 or Juno. The prospects for use of asteroid occultations to determine stellar radii and asteroid surface slopes are discussed as compared with the lunar occultation technique.

Calculations on the stability of various frosts (against evaporation) for solar system objects in circular and elliptical orbits are made. It is found that the stability of these frosts is dependent on the rate of rotation of the object, the latitude of the area on the object being considered, and the eccentricity of the orbit as well as its mean distance from the sun. These factors greatly influence the amount of solar radiation incident and reradiated from a given area on the object. The likelihood of finding these frosts on the surfaces of objects and the lifetimes of objects composed of these frosts is discussed.

Infrared reflectance spectra have shown the presence of an absorption feature in the 3-4 micron region for seven C and U asteroids. By comparison with laboratory spectra of terrestrial silicates and meteorites, it is concluded that this band is probably due to water in the form of hydrated salts and silicates (clay minerals), implying that the surface material of these asteroids may be analogous to the CI and CM carbonaceous chondritic meteorites. The presence of other hydrated minerals, however, cannot be ruled out. The depths of the water bands in the spectra vary from asteroid to asteroid, though no asteroid spectrum shows a band as deep as was detected on 1 Ceres. On four other C asteroids, no water band was detected. The implications of these observations for the mineralogy of these asteroids are discussed

Radiometric and reflected light observations of 433 Eros at high time resolution, high accuracy, and broad spectral coverage are reported. A thermal inertia model is used to estimate the thermal inertia, albedo, and size of Eros. An albedo of 0.125 plus or minus 0.025 with axes of 39.3 plus or minus 2.0 x 16.1 plus or minus 0.8 km is found. The estimate of the albedo is about 30% lower than previous estimates.

Broadband (J, H, K and L) and narrowband (1.5- to 3.7-micron) infrared photometry of Pluto has been conducted in order to check previous ambiguous observations of methane frost on the planet's surface. In detail, the match between a laboratory spectrum of methane frost and the observed spectrum of Pluto is not good. Nevertheless, the photometric observations suggest the presence of methane in some form.