The Earth’s magnetosphere is shown in blue. The Van Allen outer and inner radiation belts are located within the magnetosphere. They have been represented as two tori around Earth coloured orange. The Van Allen radiation belts were discovered as a result of an experiment designed by James Van Allen that was carried onboard the first US satellite, Explorer 1, launched in 1958. The Cluster constellation orbit in these regions.
ESA's mission Cluster consists of four identical spacecraft flying in formation between 19 000 and 119 000 km above the Earth. They study the interaction between the solar wind and Earth’s magnetosphere, or the Sun-Earth connection in 3D.