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Double Star is a Chinese mission conducted in partnership with Europe, comprising two satellites—TC-1 in equatorial elliptical orbit and TC-2 in polar elliptical orbit—launched in 2003 and 2004 by a Chinese Long March 2C to study how the Sun affects Earth’s magnetosphere. Until 2007, they operated in tandem with the four satellites of the Cluster mission to probe the key regions of the magnetosphere in depth.
The magnetosphere shields Earth by deflecting most of the stream of particles in the solar wind. However, this shield does let through some solar particles, which generate the magnetic substorms responsible for polar auroras. While the first Double Star satellite in equatorial orbit focused on the tail of Earth’s magnetosphere, where solar particles are accelerated towards the planet’s magnetic poles, the second satellite in polar orbit studied the magnetic poles and polar auroras.
Double Star carried a payload of 16 instruments, 7 from Europe. In France, the LPP (Laboratoire de Physique des Plasmas, ex-CETP) was involved in designing the STAFF and PEACE instruments, and the IRAP (Institut de Recherche en Astrophysique et Planétologie, ex-CESR) the HIA instrument. ESA and CNES funded the European instruments and contributed to data acquisition, as well as coordinating science operations.