36th DPS Meeting, 8-12 November 2004
Session 15 Icy Satellites
Poster I, Tuesday, November 9, 2004, 4:00-7:00pm, Exhibition Hall 1A

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[15.01] HST Astrometry of Saturn's Satellites: 1996--2004

R.G. French, M. Frey, R. Hock, S. Rounds (Wellesley College)

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 400 high resolution images of Saturn with the Hubble Space Telescope's WFPC2 from 1996--2004. Although the primary focus of this work was on Planetary Camera (PC) images of the rings and small inner moons, each of the PC exposures was accompanied by three wide field (WF) frames, sampling a more extensive region of the Saturn system. Using both the PC and WF images, we have determined highly accurate positions for the intermediate and small moons, especially Prometheus, Pandora, Janus, Epimetheus, Mimas, and Enceladus, with some coverage of the larger classical satellites as well. Typical accuracies are 0.02 arcsec. We employed a new distortion correction for the WFPC2 field, based on the results of Anderson and King (1999 PASP 111,1095), including a surprisingly large (up to 0.1 arcsec per year) time-dependent systematic shift in the relative positions of the four CCD chips. These new results are more extensive, and have smaller systematic errors, than our previous studies (French et al. 2003 Icarus 162, 143--170) that were restricted to the PC observations and used a less accurate distortion correction. Our results 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 the ongoing Cassini mission to Saturn.

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

The author(s) of this abstract have provided an email address for comments about the abstract: rfrench@wellesley.edu

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.