37th DPS Meeting, 4-9 September 2005
Session 62 Planetary Rings I
Oral, Friday, September 9, 2005, 9:00-10:30am, Music Concert Hall

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[62.07] Azimuthal temperature variations in Saturn's rings as seen by the CIRS spectrometer onboard Cassini

C. Ferrari (AIM/CEA/CNRS/University Paris 7), L. Spilker, S. Brooks, S. G. Edgington, B. Wallis (JPL/CalTech), J. Pearl (NASA/GSFC), C. Leyrat (AIM/CEA/CNRS/University Paris 7), M. Flasar (NASA/GSFC), CIRS Investigation Team

The thermal emission of ring particles depends both on their surface properties and on their local dynamics. In particular, the thermal gradient between day and night hemispheres is characteristic of their thermal inertia and of their rotational characteristics. The heating by Saturn and the cooling in the planetary shadow should also generate large azimuthal temperature variations which share the same dependence on these properties (Ferrari and Leyrat 2005). Finally the thermal contrast between the lit and unlit faces of the ring should vary with the vertical distribution of particles and their vertical excursion about the ring plane during their revolution around the planet. The CIRS spectrometer on board the Cassini spacecraft is able to observe most of Saturn's rings thermal emission in the infrared between 7 and 1000 \mum. An observational campaign, which is dedicated to the detection and study of these azimuthal asymmetries, began in March 2005. All three main rings A, B, and C have been observed at both low (~ 40o) and high (~130o) phase angles. First results of these observations will be presented and discussed. They will also be compared to ground-based observations of Saturn's rings made by the VISIR/VLT spectro-imager during the same period at very small phase angle (6o, Leyrat et al, this DPS). This work is supported by the Programme National de Planetologie

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Bulletin of the American Astronomical Society, 37 #3
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