Rumba, salsa, samba and tango in the magnetosphere - The Cluster quartet'sfirst year in space

The four Cluster spacecraft were successfully launched in pairs by two Russ ian Soyuz rockets on 16 July and 9 August 2000. On 14 August, the second pa ir joined the first pair in highly eccentric polar orbits, with an apogee o f 19.6 Earth radii and a perigee of 4 Earth radii. The very accurate orbita l injection and low fuel consumption mean that spacecraft operations could continue for at least two more years after the nominal two-year mission. This is the first time that the Earth's magnetic field and its environment have been explored by a small constellation of four identical spacecraft. P reliminary results show that, as predicted, with four spacecraft we can obt ain a detailed three-dimensional view of the Sun-Earth connection processes taking place at the interface between the solar wind and the Earth's magne tic field.