BeiDous -51 and -52 were launched from the Xichang Satellite Launch Centre at 0055 UTC on 22 November. The satellites were in orbit 4 hours later.
The medium earth orbit (MEO) satellites are part of of the 3rd phase of Beidou (BDS-3), helping to expand it to global navigation coverage. The orbits are at ~21,450 km, inclined at 55.5º.
These BDS-3 satellites use phased-array antennas for navigation signals, laser retroreflectors and hydrogen maser clocks.
This was the 6th BeiDou launch this year, with BeiDous -53 and -54 scheduled for launch in December.
BDS-1 provided services to China by the end of 2000, with BDS-2 covering the Asia-Pacific region by the end of 2012. BDS-3 should provide services worldwide during 2020, with a constellation of 27 MEOs, 5 geosynchronous equatorial orbit (GEO) and 3 inclined geosynchronous orbit (IGSO) satellites. This should provide global navigation services similar to GPS, GLONASS and Galileo.
The worldwide BDS-3 will use, amongst other transmissions, a frequency of 1575.42 MHz - the same as GPS L1 and Galileo E1 civil signals; and it will use multiplexed binary offset carrier (MBOC) modulation, similar to the future GPS L1C and Galileo’s E1.