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W.D. Smythe (JPL), R. H. Brown (U. of Arizona), R. M. Nelson (JPL), B. W. Hapke (U. of Pittsburgh), L. Kamp (JPL), M. Boryta (Mt. San Antonio College), K. H. Baines (JPL), G. Bellucci (Inst. di Astrofisca Spaziale), J. P. Bibring (U. de Paris Sud-Orsay), B. J. Buratti (JPL), F. Capaccioni, P. Cerroni (Inst. di Astrofisca Spaziale), R. N. Clark (USGS Denver), A. Coradini (Inst. di Astrofisca Spaziale), D. P. Cruikshank (NASA Ames), P. Drossart (Obs. de Paris-Meudon), V. Formisano (Inst. di Astrofisca Spaziale), R. Jaumann (DLR), Y. Langevin (U. de Paris Sud-Orsay), D. L. Matson (JPL), T. B. McCord (U. of Hawaii), V. Menella (Obs. di Capodimonte), P. D. Nicholson (Cornell U.), B. Sicardy (U. de Paris Meudon), C. Sotin (U. Nantes)
The Cassini spacecraft made its closest approach to Saturn’s satellite Phoebe on 2004, day 163. The Visual and Infrared Mapping Spectrometer (VIMS) instrument on Cassini obtained limited photometric information (in the wavelength range 0.4-5.1 microns) about Phoebe on the inbound and outbound legs. Of particular photometric interest is the relationship of the VIMS image cubes taken near closest approach to the images obtained on approach and departure, at lower spatial resolution - since both are needed to develop a comprehensive understanding of the phase function. The observations were obtained over phase angles from 35 to 88 degrees.
We studied spatial regions for similarities and differences in the close approach cubes. At a wavelength of one micron, the spatial regions clearly group as highly reflecting and as highly absorbing. Assuming the members of these groups are compositionally and structurally related, one can use the members of these two groups to derive scattering properties of the surface materials and, for persistent absorptions, estimate limits on the complex indices of refraction for the component materials. If the composition of the surface becomes identified (i.e. complex indices of refraction are known), then the scattering properties can be used to further constrain the state of aggregation of the surface materials.
This work is done at JPL under contract with NASA.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.