Geos was designed for geostationary (GEO) orbit to study the particles, fields and plasmas of the Earth’s magnetosphere. Unfortunately, Geos-1 was left in a low transfer orbit because of a stage-2/3 separation problem on its launch in April 1977. As a result, the Qualification Model was launched with an identical payload in July 1978 and successfully reached GEO, becoming Geos-2. In spite of its orbit, Geos-1 made a significant contribution to international magnetospheric research until its mission end in 1980. Geos-2, whose mission ended in 1985, created a huge database for magnetospheric studies and plasma research in general.

Giotto was ESA’s first cometary close flyby, and additionally ESA’s first deep space mission and first reactivation of a spacecraft. Launched from Kourou in July 1985, its flyby of Comet Halley in 1986 provided unprecedented information on this famous comet, returning over 2000 images. The closest approach of 596 km occurred on 14 March, and the mission end for the Halley flyby was on 2 April 1986. Giotto was subsequently reactivated in 1990 for the Giotto Extended Mission, for a flyby of Comet Grigg-Skjellerup, with closest approach at about 100km in July 1992.