1. NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
2. Catholic University of America, Washington, DC 20064, USA.
3. Iona College, New Rochelle, NY 10801, USA.
4. European Southern Observatory, Munich, Germany.
5. Max Planck Institute for Solar System Research, Katlenburg-Lindau 37191, Germany.
6. Observatoire de Paris-Meudon, Meudon 92195, France.
7. University of Hawaii-Manoa, Honolulu, HI 96822, USA.