China adds two satellites to navigation constellation

China successfully launched the Beidou 2C-M2 and Beidou 2C-M5 satellites on a Long March 3B vehicle from the Xichang launch centre at 1910 GMT on 19 September. The two satellites will fly in a medium Earth orbit to provide more capability to the fledgling Compass constellation. The Chinese satellite navigation system, Compass, will eventually use 35 satellites, 27 will be in medium Earth orbit with an altitude of around 21,500 kilometres, 3 satellite will fly in an inclined geosynchronous Earth orbit (inclined at 55 degrees), and 5 satellites flying in a geosynchronous Earth orbit. The constellation is designed to provide a civilian navigation service with a ground accuracy of around 10 metres and a military service with a greater accuracy.