1. Mullard Space Science Laboratory; University College London; Holmbury St. Mary UK
2. NASA Marshall Space Flight Center; NSSTC/XD12, Space Science Branch; Huntsville Alabama USA
3. Imperial College London, Space and Atmospheric Physics Group; Blackett Laboratory; London UK
4. Laboratoire de Physique Atmosphérique et Planétaire, Institut d'Astrophysique et de Géophysique; Université de Liège; Liège Belgium
5. Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
6. Massachusetts Institute of Technology; Kavli Institute for Astrophysics and Space Research; Cambridge Massachusetts USA
7. Southwest Research Institute; San Antonio Texas USA