1. Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London, Holmbury St. Mary; Dorking, Surrey UK
2. Centre for Planetary Sciences; University College London; London UK
3. Space and Atmospheric Physics Group, Blackett Laboratory; Imperial College London; London UK
4. Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
5. Atmospheric Physics Laboratory; University College London; London UK
6. Department of Physics and Astronomy; University of Leicester; Leicester UK
7. European Space Agency; Paris France