34th Meeting of the AAS Division on Dynamical Astronomy, May 2003
6 Poster Papers
Posters, Monday, May 5, 2003, 8:00pm,

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[6.07] HST Astrometry of Saturn's Small Satellites

R.G. French, C.A. McGhee (Wellesley C.)

As part of a long-term program to study Saturn's rings over the full range of inclination and phase angles accessible from Earth, we have accumulated over 300 high resolution images of Saturn and its rings with the Hubble Space Telescope's WFPC2 from 1996-2002. Using these images, we have obtained highly accurate measurements of the positions of Saturn's small moons, primarily with the PC chip of the WFPC2. A major result of these investigations is that Pandora and Prometheus are wandering chaotically from their Voyager-based ephemerides, in roughly equal and opposite directions. They seem clearly to be exchanging orbital angular momentum and energy. These results were published in French et al. 2003 Icarus 162, 143-170. In that paper, we compared the astrometric measurements to orbital predictions by R. Jacobson (personal communication), and showed that the typical astrometric accuracy of our measurements is about 0.02 arcsec. There was not room in that paper for the full set of measurements for all satellites, which we present here, and which will be submitted to the NASA Planetary Data System Rings Node. These will be useful for construction of accurate orbital models for all of the observed satellites, and for planning for the upcoming Cassini mission to Saturn.

This work was supported in part by the NASA Geology and Geophysics Program, Massachusetts Space Grant, the Keck Northeast Astronomy Consortium, and the Space Telescope Science Institute.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.