PhD in Geophysics and Space Physics, University of California, Los Angeles. 1977, joined Jet Propulsion Laboratory (JPL); has worked on the Voyager Project, the Cassini Project and conducted independent research on the origin and evolution of planetary ring systems; currently NASA research scientist, Cassini Project Scientist and a Co-Investigator, Cassini Composite Infrared Spectrometer team; has worked on Cassini since 1988.