Dynamics of Saturn's F ring and satellites from Cassini images

Saturn's F ring poses the most severe test of our understanding of the gravitational interaction between planetary rings and small, adjacent satellites in processes that are analagous to those affecting protoplanets and the surrounding matertial out of which they accreted. Although its two 'shepherding' satellites, Prometheus and Pandora, exert detectable effects on the ring, there are several unusual features that make the ring puzzling. There is mounting evidence from Cassini occultation data of a population of small (<1km) moons orbiting near the ring. Furthermore, Cassini images show that large (~500km) distortions in the ring are consistent with the effect of large (~10km) objects in ring-crossing orbits. There are also smaller (~50km) distortions in the core of the ring consistent with embedded satellites (radius <1km) on orbits perturbed by Prometheus. The proposed research will undertake a complete survey of Cassini images of the F ring in order to (i) identify and improve the orbits of the large objects so that their interactions with the ring can be understood, (ii) identify and track the smaller objects to build up a picture of the population distribution and (iii) search for unusual features of the ring that suggest the existence of more embedded objects and explain the dynamical processes associated with them. Over the timescale of the grant Cassini will witness the closest approach between the F ring and the moon Prometheus when we expect the distortions in the ring to be at a maximum. An extended mission will mean that we will have 6 years of observations of the F ring. This will give us the opportunity to study and understand all the dynamical processes that affect the ring and thereby give us a unqiue insight into the more general problems of ring-satellite and protoplanet-disk interactions.