||Double Star is a joint ESA (European Space Agency) / CNSA (China National Space Administration) project to study the effects of sun radiation on Earth's space environment (i.e., magnetosphere in geospace), in particular the 'magnetotail', where storms of high-energy particles are being generated. The DSP mission consists of two spacecraft, each designed, developed, launched, and operated by CAS/CNSA (Chinese Academy of Sciences/China National Space Administration). The orbital design of the two minisatellites considers a so-called mini-cluster with one spacecraft in near-equatorial- and the second spacecraft in polar orbit. DSP is in fact providing new measurements in key regions of the magnetosphere. The coordinated and simultaneous measurement capability of DSP with ESA's Cluster-II mission from various perspectives promises an optimum exploitation in observation returns. In China, the two spacecraft missions are referred to as TC (Tan Ce), meaning Explorer.