Affiliation: | * Space Research Institute, Profsoyuznaya 84/32, 117810, Moscow GSP-7, USSR ** Central Laboratory for Space Research, Observatory Stara Zagora, 6000, Stara Zagora, Bulgaria *** University of Besançon, 25000, Besançon, France † Centre National D'Etudes Spatiales, 31000, Toulouse, France ‡ Service d'Aeronomie CNRS, 91370, Verrières-le-Buisson, France § Observatory of Ondrejov, 25165, Prague, Czechoslovakia |