1. S. J. Ostro, R. F. Jurgens, K. D. Rosema, D. K. Yeomans, J. D. Giorgini, R. Winkler, R. Rose, S. D. Howard, M. A. Slade, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA.
2. R. S. Hudson, School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA 99164-2752, USA.
3. D. B. Campbell, National Astronomy and Ionosphere Center, Space Sciences Building, Cornell University, Ithaca, NY 14853-6801, USA.
4. J. F. Chandler and I. I. Shapiro, Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.
5. P. Perillat, Arecibo Observatory, Box 995, Arecibo, Puerto Rico 00613, USA.