The Double Star mission used two satellites in Earth orbit - each designed, developed, launched, and operated by the China National Space Administration. ESA has agreed to contribute 8 million Euros to the Double Star programme. This funding was used for refurbishment and pre-integration of the European instruments, acquisition of data for four hours per day and co-ordination of scientific operations. This schedule enabled Double Star to operate simultaneously with ESA's Cluster mission.
The first equatorial spacecraft (Double Star 1, also known as DoubleStar1, Tan Ce 1, Chinese for Explorer 1, TC-1) was launched by a Long March 2C launch vehicle on December 29, 2003, at 19:06 UTC. Its purpose was to investigate Earth's huge 'magnetotail', the region where particles are accelerated towards the planet's magnetic poles by a process known as 'reconnection'.
The second polar spacecraft (Double Star 2, also known as DoubleStar2, Explorer 2, Tan Ce 2, TC-2) was launched July 25, 2004 at 07:05 UTC, also by a Long March 2C. It focuses on physical processes taking place over the magnetic poles and the development of aurorae.
The mission formally ended on October 14, 2007, when the TC-1 spacecraft re-entered the Earth's atmosphere after being decommissioned (an unavoidable consequence of its equatorial orbit). The TC-2 spacecraft and payload continued to operate until late 2008, when contact was lost.[2]