The near-equatorial terminator ionosphere of Saturn

The Cassini orbiter has provided 12 opportunities for three-frequency radio occultations of the rings, atmosphere, and ionosphere of Saturn between May and September of 2005. By virtue of being optimized for the ring observations, these occultations provided measurements of the Saturnian ionosphere in a range of latitudes from about 7 deg. S to about 5 deg.N, and solar zenith angles of about 85 deg. to 95 deg., near both the dawn and dusk terminators. The dawn ionospheres have peak densities about a factor of 5 lower than their dusk counterparts, possibly indicating the depleting effect of water molecules migrating from the rings, while on the night side. The search for a ring ionosphere has also been carried out, and its results will be reported.