HR: 1340h
AN: P53A-1463    [Abstracts]
TI: Saturn's A Ring as Seen by the Voyager IRIS and Cassini CIRS Experiments
AU: * Brooks, S M
EM: Shawn.M.Brooks@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 230-205, Pasadena, CA 91101 United States
AU: Spilker, L J
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 230-205, Pasadena, CA 91101 United States
AU: Pilorz, S H
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 230-205, Pasadena, CA 91101 United States
AU: Edgington, S G
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 230-205, Pasadena, CA 91101 United States
AU: Wallis, B D
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 230-205, Pasadena, CA 91101 United States
AU: Pearl, J C
AF: NASA Goddard Space Flight Center, NASA GSFC Code 693, Greenbelt, MD 20771 United States
AU: Flasar, F M
AF: NASA Goddard Space Flight Center, NASA GSFC Code 693, Greenbelt, MD 20771 United States
AU: Ferrari, C
AF: CEA Saclay, Bat. 709 Orne des Merisiers Gif sur Yvette, Saclay, 91191 France
AU: Showalter, M R
AF: Stanford University, NASA Ames Research Center M/S 245-3, Stanford, CA 94305 United States
AU: Achterberg, R K
AF: SSAI, NASA GSFC Code 693, Greenbelt, MD 20771 United States
AU: Nixon, C A
AF: University of Maryland, NASA GSFC Code 693, College Park, MD 20771 United States
AU: Simon-Miller, A A
AF: NASA Goddard Space Flight Center, NASA GSFC Code 693, Greenbelt, MD 20771 United States
AU: Romani, P N
AF: NASA Goddard Space Flight Center, NASA GSFC Code 693, Greenbelt, MD 20771 United States
AB: During Cassini's successful orbital insertion manuever at Saturn its Composite Infrared Spectrometer (CIRS) obtained thermal spectra of Saturn's rings at a range of geometries not seen since the Voyager flybys. CIRS is a Fourier-transform spectrometer that measures infrared radiation from 7 microns out to 1 millimeter (1400 to 10 $ \text{cm}^{-1} $). Of the main rings, the A Ring was observed at the greatest range of phase and emission angles during Saturn orbit insertion. Scans of the lit and unlit sides of the A Ring were obtained at a spectral resolution of 15.5 $ \text{cm}^{-1} $ and at low ($ \sim 60^{\circ} $) and intermediate ($ \sim 130^{\circ} \text{-} 140^{\circ} $) phase angles. The infrared interferometer spectrometer (IRIS) experiments aboard Voyagers 1 and 2 also obtained thermal spectra of the rings. IRIS, the predecessor of the CIRS instrument, is a Michelson interferometer that records spectra between 4 and 55.5 $ \mu \text{m} $ (2500 to 180 $ \text{cm}^{-1} $). Spectra of the lit and unlit A Ring with a resolution of 4.3 $ \text{cm}^{-1} $ were obtained at phase angles somewhat lower than CIRS SOI scans ($ \sim 30^{\circ} $) and at intermediate phase angles comparable to those observed by CIRS. We will interpret Cassini observations of the A Ring in the context of the earlier Voyager observations. A Ring brightness temperatures retrieved from the SOI scans clearly show a dependence on viewing geometry, varying by $ \sim 10 \, \text{K} $. The wide range of viewing geometries provided by the two sets of observations will allow us to determine the effect of viewing geometry on the ring's brightness temperature. By separating out such viewing geometry effects, we can constrain the physical properties of the ring as a whole as well as those of its constituent particles. Additionally, the time separation between the CIRS and IRIS observations will allow us to identify any changes in ring temperatures between the Voyager and Cassini epochs as might be expected from, for example, differences in solar elevation angle.
DE: 5759 Rings and dust
DE: 6265 Planetary rings
DE: 6275 Saturn
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting