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|1 January 2004|
Double Star is a mission of the Chinese National Space Agency (CNSA) in co-operation with the European Space Agency (ESA) to explore Earth's magnetosphere - the magnetic bubble that surrounds our planet. Double Star consists of two satellites orbiting Earth.
Its data will be essential to understand how the Sun activity influences the near-Earth space and induces changes in the 'space weather' through magnetic storms, streams of high-energy particles, etc. These powerful events take place in the magnetosphere and can have serious consequences to human activities, from power cuts to damaged satellites and communication breakdowns. Double Star will help to understand these phenomena and thus minimise their negative effect.
Double Star will follow in the footsteps of ESA's ground-breaking Cluster mission, a flotilla of four identical spacecraft launched in 2000, also to explore the near-Earth environment.
The key aspect of Europe's participation is the inclusion of seven instruments identical to those flying on the four Cluster spacecraft, plus one extra instrument. They will become the first ever European instruments to be flown on Chinese satellites.
Double Star and the Cluster flotilla will work in a synchronised way. This will allow scientists to explore key regions of the magnetosphere in more detail than ever before.
Both satellites will operate in regions especially appropriate to investigate the mechanisms triggering the storms, and that remain uncovered by other missions.
ESA contributes 8 million Euro to Double Star. This covers the refurbishment, rebuilding and pre-integration of the European instruments; the acquisition of data for four hours per day; the co-ordination of scientific operations.
The two Double Star spacecraft have been launched by Chinese Long March 2C rockets. The equatorial spacecraft (TC-1) was launched from Xichang (Sichuan province (southern China) on 29 December 2003. The second (polar) spacecraft TC-2 was successfully launched from Taiyuan Satellite Launching Centre (Shanxi province) on 25 July 2004.
The equatorial spacecraft, TC-1, was launched into an elliptical orbit of 550 x 63 780 kilometres, inclined at 28.5° to the equator. The polar satellite, TC-2, has a polar orbit of 700 x 39 000 kilometres.
Planned mission lifetime
The equatorial spacecraft (TC-1) will operate for 18 months. The polar spacecraft (TC-2) will operate 12 months.
The spacecraft are called 'Tan Ce' (TC), which in Chinese means 'Explorer'.
Each Double Star spacecraft is cylindrical. They have 2.5 m experimental rigid booms and two axial telecommunication antenna booms, as well as the solar arrays.
Diameter: 2.1 m, height 1.4 m
What's on board?
16 instruments will fly on board Double Star. Europe provides half of the instruments (seven of them are identical to those currently flying on the four Cluster spacecraft) while the rest will be provided by Chinese institutes. The European instruments have been built by consortia of institutes led by Principal Investigators. They are the following:
Fluxgate Magnetometer – FGM (one on each spacecraft) Measures the magnetic fields along the orbit. FGM can take high resolution measurements with up to 67 samples per second.
Principal Investigators: C. Carr, Imperial College, United Kingdom and T. Zhang, Space Research Institute, Austria.
Active Spacecraft Potential Control experiment – ASPOC (on TC-1) Electrical charging of a Cluster spacecraft in orbit can have a severe impact on the performance of the scientific instruments. ASPOC is designed to 'earth' or neutralise the spacecraft by preventing a build up in positive electrical charge.
Principal Investigator: K. Torkar, Space Research Institute, Austria
Spatio-Temporal Analysis of Field Fluctuation experiment - STAFF/DWP (on TC-1) A magnetometer that looks at waves (i.e. rapid variations in the magnetic fields), particularly in regions where the charged particles of the solar wind interact with the magnetosphere.
Principal Investigators: N. Cornilleau-Werhlin, Centre d'étude des Environnements Terrestre et Planétaires, France and H. Alleyne, University of Sheffield, United Kingdom
Plasma Electron And Current Experiment - PEACE (one on each spacecraft) Looks at all electrons in the space plasma with low to medium energies, counts them and measures their direction of travel and speed.
Principal Investigator: A. Fazakerley, Mullard Space Science Laboratory, Space Plasma Physics Group, United Kingdom
Hot Ion Analyser experiment – HIA (on TC-1) Analyses the distribution functions of ions in the magnetosphere space plasma and in the solar wind.
Principal Investigator: H. Reme, Centre d'Etude Spatiale des Rayonnements, France
Neutral Atom Detection Unit - NUADU (on TC-2) Images the ring current, high-energy particles trapped in Earth's magnetic field.
Principal Investigator: S. McKenna-Lawlor, National University of Ireland, Ireland.
ESA Project Manager: Bodo Gramkow
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