[1] INAF, IFSI, I-00133 Rome, Italy
[2] Observ Paris, LESIA, F-92195 Meudon, France
[3] Univ Lecce, Dipartimento Fis, I-73100 Lecce, Italy
[4] DLR, German Aerosp Ctr, Opt Informat Syst, D-12489 Berlin, Germany
[5] Russian Acad Sci, Inst Space Res, Moscow 117997, Russia
[6] PAS, SRC, PL-00716 Warsaw, Poland
[7] INAF, IASF, I-00133 Rome, Italy
[8] Univ Milan, Dipartimento Meccan, Lecce, Italy