China launched a new pair of navigation satellites in the move to advance the completion of the Phase III of its Beidou program. The launch took place at 12:29 UTC from the LC launch comple of the Xichang Satellite Launch Center, using for the first time the combination of the Long March-3B rocket with the new Expedition-1 (Yuanzheng-1) upper stage.
http://www.nasaspaceflight.com/2015/07/china-long-march-3b-dual-beidou/
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The first Quasi-Zenith Satellite (QZS-1) was launched on September 11, 2010, and the Japan Aerospace Exploration Agency (JAXA) is currently operating QZSS. Afterwards, the cabinet decided in September 2011 that the government would establish a four-QZS constellation and complete a seven-QZS constellation in the future. This system is also regarded as an important political measure in the Basic Plan on Space Policy of January 2013.
Due to these circumstances, the government decided to develop the additional three satellites (two with a quasi-zenith satellite orbit [QZO] and one with a geostationary orbit [GEO]), which will be launched from FY2016 to FY2017. In this way, a four-satellite constellation will be operated from FY2018. Development and operation will be conducted via a private finance initiative (PFI) project, and Quasi-Zenith Satellite System Services Inc. (QSS) will operate the four satellites, including QZS-1.
To improve multipath errors (caused by reflection off buildings and other objects) and satellite constellation errors, it is necessary to increase the number of satellites used for positioning. However, there is not a sufficient number of GPS satellites to perform high-precision positioning with these satellites alone. And because GPS satellites are operated by the United States, the number cannot be increased. Therefore, positioning errors will be improved by increasing the number of QZS that are compatible with GPS.
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