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T. B. McCord (Univ. of HI HIGP, and Planet. Sci. Inst.), C. A. Griffith (Univ. of Az.), G. B. Hansen (Planet. Sci. Inst.), J. I. Lunine (Univ. of Az.), K. H. Baines (Jet Prop. Lab.), R. H. Brown (Univ. of Az.), B. Buratti (Jet Prop. Lab.), R. N. Clark (USGS Denver), D. P. Cruikshank (NASA Ames Res. Center), G. Filacchione (Inst. Fisica Spazio CNR), R. Jaumann (DLR-Inst. fur Planet.), C. A. Hibbitts (Planet. Sci. Inst.), C. Sotine (Univ. of Nantes), Cassini VIMS Team
Titan, the largest satellite of Saturn, has a thick atmosphere containing methane with high altitude haze that obscures the surface except for windows in the methane absorption bands at some IR wavelengths where scattering also is reduced. Chemistry models of the atmosphere suggest deep deposits of organic liquids and solids (1). Groundbased telescopic observations of Titan’s integral disk suggest the presence of water ice (2). The Cassini VIMS obtained spectra in the 0.35 to 5.1-µm range that include narrow windows in the methane spectrum near 1.6, 2.0, 2.8, and 5.0 µm where the surface might have been observed with spatial resolution up to about 100 x 200 km during the Saturn orbit insertion phase on June 30 2004. Surface albedo features seem to appear in these windows. We have analyzed Titan’s spectra in an attempt to identity the surface material(s). The VIMS spectra were averaged for several pixels for each of six regions on Titan corresponding to apparent bright and dark surface features. The spectra were calibrated to I/F as seen by VIMS and then were analyzed using radiative transfer models to remove the effects of the atmosphere (2) to estimate surface I/F values. These were then compared with candidate material reflectance at each of the spectral windows. Preliminary analysis suggests that the average results will agree with previous groundbased data analyses (2) and there is the suggestion of differences in reflectance among the surface regions analyzed so far. This work was supported by the NASA Cassini Project. (1) Lunine et al., Science, 222, 1229, 1983. (2) Coustenis et al., Icarus 118, 87, 1995; Griffith et al., Science 300, 628, 2003.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.