Spitale, J.N., Porco, C.C., Colwell, J.E., Hahn, J.E. (2008). "Kinematics of the Outer Edges of Saturn's A and B rings." American Astronomical Society, DDA meeting #39, #18.03.


Abstract
The outer edges of Saturn's A and B rings have long been known to possess non-axisymmetric shapes as a result of their proximity to inner Lindblad resonances with the Janus/Epimetheus system, and with Mimas, respectively (Porco et al. 1984). Using a large data set consisting of Cassini ISS imaging and UVIS occultation data, we re-examine the kinematics of these edges with much finer temporal and azimuthal resolution than previously possible. The A-ring outer edge shows the seven-lobed shape resulting from the resonance with Janus and Epimetheus, except at times within a few months of their orbital swap. The best-fitting 7-lobed mode precesses at a speed close to the raw mean of the satellites' orbital speeds, rather than the mass-weighted mean. The outer edge of the B ring displays the expected 2-lobed pattern forced by the resonance with Mimas, but unexplained additional large-amplitude, time-dependent components are present as well. Results of this kinematic modeling are used as inputs to a dynamical simulation to infer physical properties of the rings (Hahn et al., this conference).