Saturn's rings: 3-mm observations and derived properties |
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| Authors: | Eugene E Epstein Michael A Janssen Jeffrey N Cuzzi William G Fogarty John Mottmann |
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| Institution: | The Aerospace Corporation, Box 92957, Los Angeles, California 90009, USA;Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA;Ames Research Center, National Aeronautics and Space Administration, Moffett Field, California 94035, USA;Physics Department, University of Wisconsin, Milwaukee, Milwaukee, Wisconsin 53211, USA;Department of Physics, California State University at San Luis Obispo, San Luis Obispo, California 93407, USA |
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| Abstract: | We have used 3-mm Saturn observations, obtained from 1965 through 1977 and with Jupiter as a reference, to derive a ring brightness temperature of 18 ± 8°K. Thebrightness temperature of the disk of Saturn is 156 ± 9° K. Part of the ring brightness (≈62K) may be accounted for as disk emission which is scattered from the rings; the remainder (12 ± 8° K we attributed to ring particle thermal emission. Because this thermal component brightness temperatures is so much less than the particle physical temperature, limits are placed on the mean size and composition of the ring particles. In particular, as found by others, the particles cannot be rocky, but must be either metallic or composed of extremely low-loss dielectric material such as water ice. If the particles are pure water ice, for example, then a simple slab model and a multiple-scattering model both give upper limits to the particle sizes of ≈ 1 m, a value three times smaller than previously available. The multiple-scattering model gives a particle single-scattering albedo at 3 mm of 0.83±0.13. |
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