Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK; Institute of Atmospheric Physics, AS CR, Bocni II/1401, 14131 Prague 4 - Sporilov, Czech Republic
Institute of Atmospheric Physics, AS CR, Bocni II/1401, 14131 Prague 4 - Sporilov, Czech Republic
DESPA, Observatoire de Paris-Meudon, Place Jules Janssen, 92 190 Meudon, France