After a series of engine firings, the European Space Agency's (ESA) four Cluster satellites are flying in formation in operational polar orbits. Scientists are preparing to start the two-year mission, which will use 11 instruments to measure the effects of the solar wind on near-Earth space where high energy particles hit the magnetosphere. A series of orbit trim manoeuvres will be made by the end of this month to place the satellite quartet - Tango, Rumba, Salsa and Samba - into a tetrahedral flight formation.

The four Clusters were launched in pairs aboard two Soyuz Fregat boosters from the Baikonur Cosmodrome, Kazakhstan, on 16 July and 9 August.

Source: Flight International