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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.08.026 Byline: Andrew S. Rivkin (a), Eric L. Volquardsen (b) Keywords: Asteroids; Asteroids, Composition; Asteroid Ceres; Spectroscopy Abstract: We present observations of Ceres over the 2.2-4.0[mu]m region taken using the SpeX instrument on the NASA IRTF in 2005. The observations cover Ceres' entire longitude range and show evidence for a relatively uniform surface in terms of Ceres' composition, however there is a subtle but consistently shallower band depth over longitudes associated with bright regions in HST maps, suggesting those areas are slightly less carbonate- and brucite-rich. We also find Ceres' beaming parameter, a measure of its thermal properties, to have changed with its viewing aspect. Author Affiliation: (a) Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., MP3-E169, Laurel, MD 20723-6099, USA (b) Institute for Astronomy, University of Hawaii, Hilo, HI 96720, USA Article History: Received 2 June 2009; Revised 17 July 2009; Accepted 30 August 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.10.034 Byline: Eric L. Volquardsen (a), Andrew S. Rivkin (b), Schelte J. Bus (a) Keywords: Asteroids; Asteroids; composition; Spectroscopy; Asteroids; surfaces Abstract: Near-infrared spectra of the near-Earth object (100085) 1992 UY4 are similar to those of P-type asteroids, providing a fitted geometric albedo of 0.052[+ or -]0.005 and an effective diameter of 1.68[+ or -]0.08km. This object, with a likely outer-belt origin, also exhibits a 3-[mu]m absorption feature with a band depth of 3%[+ or -]1%, corresponding to a regolithic bulk hydrogen-to-silicon ratio of 0.30[+ or -]0.05. The bulk of this hydrogen seems to be present in H.sub.2O-dominated minerals. Author Affiliation: (a) Institute for Astronomy, University of Hawaii, Hilo, HI 96720, USA (b) Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA Article History: Received 29 March 2006; Revised 25 October 2006

We observed near-Earth Asteroid (NEA) 2002 CE26 in August and September 2004 using the Arecibo S-band (2380-MHz, 12.6-cm) radar and NASA's Infrared Telescope Facility (IRTF). Shape models obtained based on inversion of our delay-Doppler images show the asteroid to be 3.5 [+ or -] 0.4 km in diameter and spheroidal; our corresponding nominal estimates of its visual and radar albedos are 0.07 and 0.24, respectively. Our IRTF spectrum shows the asteroid to be C-class with no evidence of hydration. Thermal models from the IRTF data provide a size and visual albedo consistent with the radar-derived estimate. We estimate the spin-pole to be within a few tens of degrees of [lambda] = 317[degrees], [beta] = -20[degrees]. Our radar observations reveal a secondary approximately 0.3 km in diameter, giving this binary one of the largest size differentials of any known NEA. The secondary is in a near-circular orbit with period 15.6 [+ or -] 0.1 h and a semi-major axis of 4.7 [+ or -] 0.2 km. Estimates of the binary orbital pole and secondary rotation rate are consistent with the secondary being in a spin-locked equatorial orbit. The orbit corresponds to a primary mass of M = 1.95 [+ or -] 0.25 x [10.sup.13] kg, leading to a primary bulk density of [rho] = 0.9 + 0.5/-0.4 g [cm.sup.-3], one of the lowest values yet measured for a main-belt or near-Earth asteroid. Keywords: Asteroids; Asteroids, composition; Asteroids, surfaces; Radar observations