Cooper, N. J., Murray, C. D., Beurle, K., Evans, M. W., Porco, C. C. (2005). "Astrometry and dynamics of Polydeuces, a new co-orbital satellite of Dione." American Astronomical Society, DPS meeting #37, #36.04.


Abstract
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 retargeting, 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 modeling, 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.