The Double Star project is a Chinese National Space Administration (CNSA) mission. ESA and CNES took part in the programme by funding European instruments (providing Cluster instruments spares), part of the data collection, as well as coordinating scientific operations.
The Double Star programme’s mission was to follow up on the European Cluster mission and study the effects of the Sun on Earth’s magnetosphere. Each satellite was on a specific orbit:
- The first satellite (TC-1) was on an elliptical equatorial orbit so it could study Earth’s magnetotail, an area in which particles are accelerated towards the planet’s magnetic poles by the magnetic reconnection phenomenon.
- The second satellite (TC-2) was on an elliptical polar orbit and focused on physical processes occurring above the magnetic poles and auroras.
Double Star satellites were equipped with 16 instruments, 7 of which were identical to those found aboard Cluster satellites. Satellites from both projects worked in synchronisation in order to provide a more detailed exploration of key areas in the magnetosphere. The European instruments were:
- FGM : Flux Gate Magnetometer(1 on each satellite), to measure the continuous magnetic field.
- ASPOC : Active Spacecraft POtential Control experiment (on TC-1), an experiment to control the satellite’s potential using ion emissions.
- STAFF and DWP : Spatio-Temporal Analysis of Field Fluctuation experiment et Digital Wave Processing (TC-1), a magnetometer to study fast fluctuations of the magnetic field, particularly in areas where the solar wind’s charged particles interact with the magnetosphere. Principal investigators: N. Cornilleau-Werhlin, CETP, France on STAFF, and H. Alleyne, Sheffield University, United Kingdom for DWP.
- PEACE : Plasma Electron And Current AnalysEr (one on each satellite), to study all low and middle-energy electrons within the plasma.
- HIA : Hot Ion Analyzer experiment (TC-1), to analyse ion distribution functions within the magnetosphere, space plasma, and solar wind. Principal investigator: H. Reme, IRAP (Institut de Recherche en Astrophysique et Planétologie, ex-CESR), France
- NUADU : Neutral Atom Detection Unit (on TC-2), to create images of high-energy particles captive of Earth’s magnetic field.
The two Double Star satellites were launched using Chinese Long March rockets. TC-1 was launched on December 23rd 2009 from Xichang (in the Sichùan province), and TC-2 was launched on July 25th 2004 from Taiyuan (in the Shanxi province).