The launch of Beidou-3M5 and -3M6 medium earth orbit (MEO) spacecraft took place at 0140 UTC from the Xichang Satellite Launch Centre, using a Long March-3B launch vehicle. It took >4 hours to complete the mission.
The satellites, also designated Beidou-33 and -34, are part of the third phase of the system and are expected to occupy a ~21,500 km nominal orbit at 55.5º inclination.
The Beidou Phase III system includes the migration of its civil signals to a frequency of 1575.42 MHz, the same as GPS L1 and Galileo E1 civil signals, and its transformation to a multiplexed binary offset carrier (MBOC) modulation - similar to the future GPS L1C and Galileo E1.
Current real-time, stand-alone BeiDou (95%) positioning accuracy has been quoted as <6 m horizontal and <10 m vertical.
BeiDou (or Compass) was approved by the Chinese government in 2004. Phase 1 was an experimental regional navigation system. Phase 2, from 2012, provides an open service over China and the regional area. Phase 3, including this launch, should provide full operational capability (FOC) by 2020, with a constellation of 27 MEOs plus 5 geostationary (GEO) and the existing 3 inclined geosynchronous orbit (IGSO) satellites of the regional system.
BeiDou FOC should provide global navigation services compatible with GPS, GLONASS and Galileo.
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