1. E. R. Kursinski, Division of Geological and Planetary Sciences and Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125, USA.
2. G. A. Hajj, W. I. Bertiger, S. S. Leroy, T. K. Meehan, L. J. Romans, J. T. Schofield, D. J. McCleese, W. G. Melbourne, C. L. Thornton, T. P. Yunck, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
3. J. R. Eyre, United Kingdom Meteorological Office, Bracknell, Berkshire RG12 2SZ, UK.