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K. S. Noll (STScI), J. Luu (Leiden Univ.)
We have begun a program of spectrophotometric observations of five objects in the Kuiper Belt (KBOs) using NICMOS on the Hubble Space Telescope. Most observations will be made using NIC2 and moderate or broad bandwidth filters chosen to sample key wavelengths. In particular, we have chosen filters that can identify the presence of water ice. The first observation made in this program was spectrophotometry of the KBO 1997CT29. The spectrum of 1997CT29 has two distinguishing characteristics evident in its spectrum. It is an extremely red object with V-K > 4 (V-K for the Sun is 1.43), making it redder over this wavelength interval than any other known KBO or Centaur. The second distinguishing feature of 1997CT29 is the evidence for an absorption band between 1.9 and 2.2 um . A weaker absorption may be present near 1.45 um . Both features would be consistent with the presence of water ice absorption features in the spectrum. Water ice has recently been detected in the spectrum of Centaur 1997CS29 (Brown et al. 1998). We are scheduled to observe four additional KBOs, 1996TP66, 1996TO66, 1996TS66, and 1996TQ66, some before October. Together with other spectra of KBOs obtained with HST and ground based telescopes, there is the prospect of spectra sufficient to identify strong absorbers on more than 10 KBOs and Centaurs by the end of 1998. With a sample this size it may just begin to be possible to search for patterns in color and spectral features in these objects that may provide clues to compositions and surface histories for objects in the Kuiper Belt.