[1] UNIV OXFORD, DEPT ASTROPHYS, OXFORD, ENGLAND
[2] CENS, DPH SAP, F-91191 GIF SUR YVETTE, FRANCE
[3] INST SPACE & ASTRONAUT SCI, SAGAMIHARA, KANAGAWA 229, JAPAN
[4] CNR, IST ELETTRON STATO SOLIDO, I-00153 ROME, ITALY
[5] OSSERVATORIO ASTRON CAPODIMONTE, I-80131 NAPLES, ITALY
[6] UNIV MILAN, DEPARTIMENTO FIS, SEZ ASTROFIS, I-20133 MILAN, ITALY
[7] OBSERV PARIS, F-92190 MEUDON, FRANCE
[8] UCL, MULLARD SPACE SCI LAB, DORKING RH5 6NT, SURREY, ENGLAND
[9] EUROPEAN SPACE AGCY, EUROPEAN SPACE RES & TECHNOL CTR, DEPT SPACE SCI, 2200 AG NOORDWIJK, NETHERLANDS