Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 1984
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984icar...58..403e&link_type=abstract
Icarus (ISSN 0019-1035), vol. 58, June 1984, p. 403-411.
Astronomy and Astrophysics
Astronomy
20
Brightness Temperature, Radio Sources (Astronomy), Saturn Rings, Albedo, Ice, Jupiter (Planet), Millimeter Waves, Particle Size Distribution, Saturn, Rings, Observations, Physical Properties, Inclination, A Ring, Brightness, Temperature, Optical Properties, Depth, B Ring, C Ring, Particles, Thermal Properties, Emissions, Disk, Comparisons, Models, Composition, Size, Ice, Water, Scattering, Albedo, Calculations, Theoretical Studies, Refractivity, Radius, Distribution, Absorption, Density, Porosity, Silicate,
Scientific paper
To determine a more precise brightness temperature and more accurate properties for Saturn's rings, 3.3 mm low inclination observations have been made at 90 GHz with the Aerospace 4.6 m radio telescope. A mean brightness temperature of 17 plus or minus 4 K has been determined by comparing the data with the variation of the inclination of the total flux from the planet and rings predicted by a simple model with uniformly bright A and B rings. Variation of the normal optical depth from 0.4 to 1.0 resulted in a total variation of about 1.5 K in A and B brightness. A portion of the brightness attributed to ring particle thermal emission has been determined to be at a temperature of 11 plus or minus 5 K. If the maximum particle radius (approximately 5 m) deduced from Voyager bistatic radar observations is correct, results indicate a particle distribution ranging between 1 cm and several meters radius of the form r exp -s with s = 3.3-3.6, or a material absorption coefficient ranging between 3 and 10 times lower than that of pure water ice at 85 K, or both. An increase in the porosity of the ice particles through a decrease in their density will not produce the observed particle albedo. If the rocky material is uniformly distributed, low ring brightness temperature would allow a silicate upper limit of approximately 10 percent by mass; however, the silicate material could be more abundant if it is separated from the icy material.
Cuzzi Jeff N.
Epstein Eugene E.
Janssen Michael A.
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