Full-disk observations of the saturnian moons in the VIS-NIR spectral range by Cassini- VIMS

During the first two years of the Cassini's nominal mission, VIMS (Visual and Infrared Mapping Spectrometer) has explored the whole system of Saturnian icy satellites. Here we report a comparative analysis of more than 600 full-disk observations obtained from July 2004 to nowadays for 15 regular and minor satellites: Atlas, Prometheus, Pandora, Janus, Epimetheus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione, Rhea, Hyperion, Iapetus and Phoebe. These observations, done from the equatorial plane, are particularly suitable to highlight the spectral differences between the leading and trailing sides of the regular satellites as function of the illumination angle (Filacchione et al., 2006a, 2006b); a byproduct of this activity is the measurement of the phase curves. The combined use of several VIS and IR spectral quantities (e.g. spectral slopes, water ice bands strengths, continuum levels, etc.) allows to find correlations between classes of satellites orbiting at different distances from Saturn: in this way it is possible to discriminate the almost pure ice surfaces of Enceladus and Calypso from the organic rich Hyperion, Iapetus and Phoebe (Tosi et al., 2006). This research was completed thanks to the support of the Italian Space Agency (ASI), Grant ASI/Cassini I/031/05/0. Filacchione et al., 2006a. Saturn's icy satellites investigated by Cassini-VIMS. I. Full-disk properties: 350-5100 nm reflectance spectra and phase curves, Icarus, in press. Filacchione et al., 2006b. VIS-NIR Spectral Properties of Saturn's Minor Icy Moons. 37th LPSC, abstract no.1271 Tosi et al., 2006. Iapetus, Phoebe and Hyperion: Are They Related? 37th LPSC, abstract no.1582