Global BeiDou grows to 21 with latest launch

Seven-ninths of the way there! The 21st satellite of the BeiDou-3 global constellation, destined to number 27 upon completion, successfully launched from Xichang on June 24. Once in final orbit and commissioned, it will become the second of three planned inclined geosynchronous orbit (IGSO) satellites, traipsing in figure-eight loops across the skies above China and neighbors in the Asia-Pacific region.

The IGSO trio will play a key role in the expansion of BeiDou-3 from a regional to a global system, in that they may afford the Asia-Pacific region greater BeiDou-derived accuracy and availability — the so-called “optimized coverage” — than will be accessible to users of the constellation in other areas of the world.

The new satellite, like others of its latest generation, will establish inter-satellite ranging links, and carries new-gun rubidium atomic clocks and passive hydrogen maser clocks. It weighs 450 kg, a gain over previous generations, with a phased array antenna for navigation signals, a laser retroreflector and deployable S/L-band and C-band antennas.

While BeiDou-3 has widespread applications in construction, transportation, fishing, power grid, disaster response, public security, smart cities and more, it will also bring increased capability — and independence from GPS — to the People’s Liberation Army. At 2 million strong with modernizing equipment, this is a force to be reckoned with in an increasingly unsettled region, with China actively pursuing numerous territorial disputes.

BeiDou-3 is migrating its civil or B1 signal from 1561.098 MHz to 1575.42 MHz, the same as the GPS L1 and Galileo E1, and changing from a quadrature phase shift keying modulation to a multiplexed binary offset carrier modulation similar to Galileos E1 and the pending GPS L1C.