Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006dps....38.7202b&link_type=abstract
American Astronomical Society, DPS meeting #38, #72.02; Bulletin of the American Astronomical Society, Vol. 38, p.628
Astronomy and Astrophysics
Astronomy
1
Scientific paper
We have measured the bulk radar reflectance properties of Enceladus, Tethys, Dione, and Rhea with the Arecibo Observatory's 13 cm wavelength radar system during the 2004, 2005, and 2006 oppositions of the Saturn system. The transmitted signal was circularly polarized and echoes were received in both the opposite circular (OC) sense to that transmitted and the same circular (SC) sense. Comparing to the icy Galilean satellites, the total radar albedos (OC+SC) of the Saturnian satellites are systematically lower for a given optical albedo. The radar albedos of Rhea and Tethys are most similar to Ganymede while Dione is most similar to Callisto. Enceladus's albedo falls between those of Ganymede and Europa. The circular polarization ratios (SC/OC) of the Saturnian satellites range from 0.7 to 1.2, and are on average lower than those of the icy Galilean satellites at this wavelength. For each satellite the 13 cm wavelength radar albedo and polarization ratio are lower than similar measurements made recently by the Cassini RADAR experiment at 2.2 cm wavelength (Ostro et al. 2006, Icarus, v183, 490). Overall, these satellites' bulk radar properties suggest subsurface multiple scattering to be the dominant reflection mechanism although operating less efficiently than on the large icy moons of Jupiter. Furthermore, these high radar albedos with, for ice, only moderate polarization ratios may present a problem for current models of such scattering mechanisms. If regolith development on these Saturnian moons is similar to that on the Jovian moons then the difference in radar properties must be attributed to a compositional difference such that the Saturnian satellite surfaces contain an additional radar absorbing component. The degree of variation in radar properties with wavelength on each satellite may constrain the thickness and efficiency of the scattering layer. We acknowledge support by NASA's Planetary Astronomy and PG&G programs.
Black Gregory J.
Campbell Don B.
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