1. Max Planck Institute for Solar System Research Göttingen Germany
2. Rheinisches Institut fuer Umweltforschung Abteilung Planetforschung Cologne Germany
3. Space Sciences Laboratory University of California Berkeley California USA
4. NASA Goddard Space Flight Center Greenbelt Maryland USA
5. Laboratory for Atmospheric and Space Physics University of Colorado Boulder Boulder Colorado USA
6. Department of Physics and Astronomy University of Iowa Iowa City Iowa USA
7. Institute of Space Research Moscow Russia