37th DPS Meeting, 4-9 September 2005
Session 36 Icy Satellites I
Oral, Wednesday, September 7, 2005, 11:45am-12:45pm, Law LG19

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[36.04] Astrometry and dynamics of Polydeuces, a new co-orbital satellite of Dione

N.J. Cooper, C.D. Murray, K. Beurle, M.W. Evans (Queen Mary, University of London), C.C Porco (CICLOPS-SSI)

Polydeuces (S/2004 S 5) is the third confirmed new satellite of Saturn to be discovered by the Cassini ISS team and is dynamically perhaps the most exotic found so far. It was first seen in two pairs of ISS WAC images taken on 2004 October 21, covering a time-span of less than 6 minutes. Following the initial discovery (IAUC 8432), further observation and orbital refinement proceeded in tandem, allowing successful recovery and retargetting, so that the total number of confirmed observations currently stands at 119, covering a time span of approximately 406 days. Initial orbit fits, based on a uniformly precessing ellipse model immediately suggested that Polydeuces might be a co-orbital of Dione (Porco et al., 2005, Science, 307, 1226). Further modelling, based on numerical solutions of the full equations of motion have confirmed this and moreover show that Polydeuces is executing tadpole motion around the L5 Lagrangian point of Dione, with a libration amplitude which varies between +21.16 ± 0.03 deg and -31.68 ± 0.06 deg, over a period of 791.3 ± 0.1 days.

NJC, CDM, KB and MWE thank the U.K. Particle Physics and Astronomy Research Council for financial support.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.