Space Weather influence Space Weather influence on satellite based on satellite based navigation and precise navigation and precise positioning positioning R. Warnant, S. Lejeune, M. Bavier R. Warnant, S. Lejeune, M. Bavier Royal Observatory of Belgium Royal Observatory of Belgium Avenue Circulaire, 3 Avenue Circulaire, 3 B-1180 Brussels (Belgium) B-1180 Brussels (Belgium)