曝光臺 注意防騙 網(wǎng)曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費者

Commercial applications of Beidou are also having trouble get-ting off the ground. A receiver unit for the first-generation Beidou system costs about $2,500, more than 10 times the cost of a GPS unit (Pollpeter, 2007). It is unclear how much a receiver for the second- generation system, which is not yet operational, will cost. In any case, since there is no charge to use the public GPS signal, Beidou seems unlikely to displace GPS in commercial applications, except perhaps in China. It is possible, however, that commercial navigation systems could eventually employ Beidou as a supplement to GPS signals.
Other Satellites
Shijian
The Shijian (“Prototype”) series is a long-running space-science and technology demonstrator program. The first satellite in the series, Shijian 1, launched in 1971, was the second satellite launched by China (the first, launched in 1970, was called Dongfanghong and carried only a radio transmitter). Currently, nine satellites in the series are operating: Shijian 6A, 6B, 6C, 6D, 6E, 6F, 7, 11-01, and 12. The Shijian 6 series was launched into LEO in three pairs between September 2004 and October 2008. According to the Chinese government, the Shijian 6 mission is “exploration of space environment, radiation in space and their influence, parameters of physical environment of the space, and other related space experiments” (“Shijian Series,” 2010). However, few details about the satellites have been revealed by Chinese media, and the launch dates have been announced only 24 hours in advance. Some sources reportedly suspect that they are signals-intelligence or electronic-intelligence satellites (“UCS Satellite Database”; “Shijian Series,” 2010).
Shijian 7, launched in July 2005, is in an orbit that is similar, albeit somewhat lower, than that of the Shijian 6 series (555 km × 570 km vs. 590 km × 605 km). Shijian 11-01, launched in November 2009, is in a distinctly higher orbit (690 km × 705 km). As is the case with the Shijian 6 series, little information about Shijian 7 and Shi-jian 11-01 has been released, other than to say that they will monitor the space environment and/or conduct space-science and engineering experiments (“UCS Satellite Database”; “Shijian Series,” 2010).
Shijian 12 was launched, on similarly short notice, in June 2010. Over the following two months, it was maneuvered into an orbit nearly identical to that of Shijian 6F, and on August 19 it approached Shi-jian 6F so closely that it may have actually made contact with it, the first known instance in which a non-U.S. satellite has conducted such a rendezvous (the United States has conducted similar operations in the past). Such a capability has multiple potential applications, such as clearing space debris, inspecting and repairing satellites, or docking with a space station such as the Tiangong module that China plans to put up next year. Another possibility, however, would be to damage or interfere with an enemy satellite (“Shijian Series,” 2010; Courtland, 2010).
　
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