The four satellites are studying the effects of solar wind on the Earth’s magnetic field – energy particles transmitted from the sun, known as solar wind, considerably influence life on Earth. Talking simultaneous measurements, they have provided the first detailed, three-dimensional analysis of the changes and processes taking place in near-Earth.

The Cluster II satellites were built to replace the original four-satellite Cluster mission which was aborted after Ariane 5’s maiden flight in June 1996 failed to launch the satellites. This unique project was then resumed with Astrium as the lead industrial contractor for the development and the replicas.

The Cluster II mission lifetime was originally from February 2001 to December 2005; however, ESA has approved another extension to December 2014, subject to a mid-term review in 2012.