Cluster II: Plasma measurements in three dimensions Original Research Article

After the dramatic accident of the first Ariane 5 rocket on 4 June 1996, causing the loss of the four European Space Agencyʹs Cluster spacecraft, a recovery programme was initiated. During 10 months, alternative studies and intense negotiations were conducted with industry, and on 3 April 1997, the ESA Science Programme Committee agreed on the re-flight of the full Cluster mission. The four satellites will be launched in pairs by two Russian Soyuz launchers in June and July 2000. The main goal of the ClusterII mission is to study, in three dimensions, the small-scale plasma stuctures in the key plasma regions: solar wind and bow shock, magnetopause, polar cusps, magnetotail, and auroral zone. The relative distance between the four spacecraft will be varied between 200 and 18000 km during the course of the mission. The Cluster II spacecraft have state-of-the-art plasma instrumentation to measure electric and magnetic fields, from quasi-static up to high frequency, and electron and ion distribution functions from around 0 eV to a few MeV in energy. The science operations are coordinated by the Joint Science Operation Centre in Rutherford Appleton laboratory (UK) and implemented by the European Space Operation Centre (Germany). A data distribution system, constituted of eight data centres, has been implemented for the production of physical parameters and their distribution to the end users all over the world. The latest information on Cluster II can be found on the Web at: http://sci.esa.int/cluster/.