1. NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-1000
2. Department of Geosciences, San Francisco State University, San Francisco, CA 94132, and NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035-1000
3. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822
4. Joint Astronomy Center, 660 North Aohoku Place, University Park, Hilo, HI 96720
5. Observatoire de Paris, 5 Place Jules Janssen, 92195 Meudon Cedex, France
6. Laboratoire de Glaciologie et Geophysique de l'Environnement, BP 96, 38402 Saint-Martin d'Heres, France
7. Jet Propulsion Laboratory, MS 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109
8. Sterling Software Inc., 1121 San Antonio Road, Palo Alto, CA 94303, and NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-1000