TC 1, 2 / Double Star 1, 2

TC 1 (Double Star E) [ESA]

The Double Star spacecraft, called also Tan Ce (TC) which in Chinese means ‘Probe‘, is a joint Chinese and ESA mission to study the effect of the Sun on the Earth's environment. The polar spacecraft (TC-2) will monitor the energy input from the solar wind into the polar ionosphere. The equatorial spacecraft (TC-1) will investigate the so-called substorm process, when it is in the Earth's magnetotail, and the entry of solar particle on the front side of the magnetosphere.

The geomagnetic substorm is a process by which energy is stored and released in the magnetosphere resulting in serious disturbances in the Earth environment. The two TC spacecraft located near the Earth and Cluster located further down the tail will help to locate the starting point of the substorm and the physical mechanism responsible for it.

The Double Star orbits have been designed such as to get the best conjunctions with Cluster in the key scientific regions.

Double Star's scientific objectives are to:

• Study the magnetic reconnection at the magnetopause and in the magnetotail
• Understand and locate the trigger mechanism for magnetospheric storms and substorms
• Study physical processes such as particle acceleration, diffusion, injection, and up-flowing ions during storms
• Study temporal variations of field-aligned currents and the coupling between tail current and auroral current.

The orbit of the DSP equatorial satellite (TC-1) is planned to have a perigee at 550 kilometers and apogee at 66 970 kilometers; the orbit of the DSP polar satellite (TC-2) is planned to have a perigee at 700 kilometers and apogee at 39 000 kilometers. The equatorial satellite of DSP will detect the physical processes of geospace storms in the near-Earth magnetotail and the energy transfer from the solar wind to the magnetosphere. The polar satellite of DSP will detect energy transfer from solar wind to magnetosphere via dayside magnetopause. The polar satellite of DSP will detect energy transfer from solar wind and near-earth magnetotail to polar ionosphere and upper atmosphere, as well as to detect ionised-particle transfer from ionosphere to magnetosphere.

The two DSP satellites will operate in the near-Earth equatorial region, the main active regions of magnetospheric storms, substorms, and particle events that are not covered by the current International Solar-Terrestrial Programme missions. The combination of two satellites forms an independent unique constellation-like exploring system that can explore the generation mechanism and evolving process of geospace storms. Cluster and DSP satellites will operate simultaneously and form for the first time a mini-constellation with 6 points in the magnetosphere.