China GPS rival Beidou
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Missile guidance
Beidou - which translates as the Big Dipper - promises to offer civilian users positioning information correct to the nearest 10 metres, measure speeds within 0.2 metres per second, and provide clock synchronisation signals accurate to 0.02 millionths of a second.
The Chinese military will be able to obtain more accurate data.
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The seeds of China’s global navigation project were planted in 1983 after a proposal was made by Chen Fangyun to develop a regional navigation system using two satellites in geosynchronous orbit in contrast to the system utilized by the United States’ GPS. In 1989, using two in-orbit DFH-2/2A communications satellites, the two-satellite concept was proven comparable to the United States’ GPS in terms of precision. The Beidou-1 program was approved in 1993 after this successful demonstration using the DFH-3 satellite as the platform, and the first two indigenous Beidou experimental navigation satellites were launched in 2000. The final Beidou-1 constellation consists of four geosynchronous satellites: Two operational satellites and two satellites to serve as backups.
The two-satellite concept achieved similar accuracy to the United States’ GPS, but it did have its drawbacks. On the other hand, it did provide for a China with only two satellites an indigenous, independent, high-accuracy military navigation system that could function in anything less than total war with a major military power as well as support military communications.
Despite the success of the two-satellite system, the geosynchronous system was limited to the Asia-Pacific region in terms of coverage and that along with its other limitations prevented its marketability in certain areas of the commercial global navigation market. To meet this challenge, China formed a private company to develop the commercial capabilities of the Beido system and a announced in 2006 the deployment of a supplementary system to the geosynchronous Beido system.
This second phase, Bediou-2, was envisioned to consist of a constellation of 35 satellites. Five of the satellites would reside in geostationary orbit. The other thirty satellites of the system were to occupy medium-earth-orbit (12-hour, 55 deg inclination, 11,339 nautical mile (21,000km) altitude circular orbits) and use the same navigation principle as the United States’ GPS. These thirty satellites were planned to provide two-levels of service. The first, a public service, would be free to China’s citizens and have an accuracy up to 10 meters. The second service would be a more accurate military signal that would also provide system status information for the constellation and the capability to manage military communications.
The ultimate goal of the Bediou-2 medium-orbit global navigation system was to represent a new regional independence from foreign global navigation systems for China’s civilian-sector and for the use of commerce, and to provide a lucrative income for China’s private subsidiaries, who currently look to systems such as the GPS.
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