Affiliation: | (1) The Astronomical Institute at Utrecht, Utrecht, The Netherlands;(2) Royal Netherlands Meteorological Institute, De Bilt;(3) Sonnenborh Observatory University, Utrecht;(4) Astronomical Observatory, Ondr jov, Czechoslovakia;(5) Observatory and Astrophysics Laboratory, University of Helsinki, Helsinki, Finland;(6) European Space Research and Technology Centre (Estec), Noordwijk |