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M. S. Kelley (NASA Johnson Space Center), P. S. Hardersen, M. J. Gaffey (Earth & Env. Sci., Science Center, Rensselaer Polytechnic Inst.)
SpeX is a medium-resolution 0.8-2.5 micron spectrograph built at the Institute for Astronomy (IfA) for the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. In June of this year SpeX became available to observers on a shared-risk basis. On June 27-30 the first asteroid observations with SpeX were performed. A summary of the preliminary results of those observations will be reported. During the course of the observing run SpeX performance was excellent with no instrument downtime. The user interface is similar to that of the NSFCAM instrument at the IRTF. Observers familiar with the NSFCAM interface will find that of SpeX more advanced, but still fairly straightforward to learn. This new instrument has several observing modes that vary in resolution. The 0.8-2.5 micron single-prism (or low resolution) mode is useful for solid, rocky bodies whose spectra may exhibit relatively broad absorption features in this region. A variety of asteroids were observed over the course of the four nights with seeing conditions on two nights that approached the theoretical limit for the IRTF. These targets were primarily members of dynamical asteroid families, which were in keeping with the nature of the project that was awarded time. Taxonomic types observed included F, M, P, S, and V, as well as several unclassified asteroids. In addition, a few targets of opportunity were observed, some of which are potential family remnants or escapees. Perhaps the most prominent among these favorable asteroids was 433 Eros. Zappala et al. (1997, Icarus 129, 1-20) suggested that Eros may have originated as part of the Maria asteroid family. Though more recently Eros has been the subject of scrutiny by the NEAR-Shoemaker spacecraft. Preliminary spectra of the asteroids from these new, ground-based observations using SpeX will be presented.