1. Space Telescope Science Institute, Baltimore, MD 21218, USA.
2. Universite de Liege, Institut d'Astrophysique, B-4000 Liege, Belgium.
3. Southwest Research Institute, San Antonio, TX 78228, USA.
4. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
5. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
6. Laboratorie d'Astronomie Spatiale, BP 8, 13376 Marseille, Cedex, 12 France.
7. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA.
8. University of Hawaii, Institute for Astronomy, Honolulu, HI 96822, USA.
9. Jet Propulsion Laboratory, Pasadena, CA 91109, USA.
10. Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ 86011, USA.
11. U.S. Geological Survey, Flagstaff, AZ 86001, USA.
12. Southwest Research Institute, Division 15, Boulder, CO 80302, USA.
13. Department of Physics, Georgia Southern University, Statesboro, GA 30460, USA.