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D. J. Tholen (Institute for Astronomy, University of Hawaii)
In 1995, the equatorial plane of the Saturnian system swept over the orbit of the Earth, presenting the ring system as well as the orbits of the major satellites edge-on, which produced a series of mutual occultation and transit events. Accurate timing of the resulting lightcurves can be used to improve the ephemerides of the satellites, which are needed to support the Cassini spacecraft mission to Saturn.
In 1997, the equatorial plane of the Jovian system swept over the orbit of the Earth, producing a similar series of mutual events involving the Galilean satellites. Those involving Io are of particular interest, because they can be used to improve the orbit of Io, in hopes of detecting any secular acceleration in its orbit, which can then be compared with theoretical expectations based on the observed heat flow.
Over a dozen of these events were successfully observed from either the University of Hawaii 2.24-m telescope (in the case of the Saturnian events) or the 0.61-m telescope (in the case of the Jovian events) on Mauna Kea. In all cases, fast subarray readout of a CCD was used to achieve time resolution of about 0.1 to 0.5 seconds. The results from these observations will be presented.