Spitale, J., Porco, C. C., Jacobson, R. A., Owen, W. M., Charnoz, S., Brahic, A., Murray, C. D., and Evans, M. W. (2004). "Cassini Imaging Science: Orbits of Moons and Rings." Eos Trans. AGU 85(47), Fall Meet. Suppl., Abstract P52A-01.


Abstract

We report on the orbits of several small Saturnian satellites, either recovered or newly-discovered in recent Cassini imaging observations. The mean motions of Pan and Atlas have been corrected based on recent Cassini imaging combined with Voyager observations. Two small satellites, S/2004 S 1 and S/2004 S 2, have been discovered between the orbits of Mimas and Enceladus on orbits that are nearly circular and uninclined. Both bodies were observed for a fraction of one orbit on June 1, 2004 and S/2004 S 1 was subsequently detected in images shuttered three weeks earlier. Those bodies may be recovered in late October in imaging sequences designed for that purpose. A third new object, S/2004 S3, was detected in images from June 21, 2004, orbiting just outside the F ring. A search for additional detections revealed a fourth object, S/2004 S4, orbiting interior to the F ring near the longitude at which the new object would be expected 5 hours later. A low-residual orbit that crosses the F ring explains all of the observations, but it is not yet clear whether the two sequences imaged the same object or two different objects coincidentally found orbiting at the same longitude but at different orbital semimajor axes. These issues make the nature of these objects -- solid satellites or F ring clumps -- unclear. In addition, Cassini images have been used to develop a kinematical model for the F-ring model. The data, fitting procedures, and results of these orbital analyses will be discussed.