1. Kitt Peak National Observatory, Tucson, Arizona 85726
2. Space Sciences Institute, University of Southern California Tucson Laboratories, Tucson, Arizona 85713
3. Planetary Science Institute, Pasadena, California 91101
4. Jet Propulsion Laboratory, Pasadena, California 91103
5. University of Michigan, Ann Arbor 48109
6. Johns Hopkins University, Baltimore, Maryland 21218
7. Service d'Aeronomie du CNRS, Paris, France
8. Naval Research Laboratory, Washington, D.C. 20375
9. York University, Ontario, Canada M3J 1P3
10. Harvard University, Cambridge, Massachusetts 02138