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

Although publicly available signals from the U.S. GPS system can also be used to support these functions, China’s Compass system will likely be able to provide higher-precision position and timing than the public GPS signals. Having its own PNT satellite system, moreover, ensures China against a cutoff of the U.S. public GPS signal, however unlikely that may be (as civilian commerce becomes increasingly reli-ant on GPS, the economic disruption caused by a shutoff would be significant). Finally, since the Compass system uses different frequen-cies than the GPS system, China’s military could jam GPS frequencies, thus denying the United States or other countries access to the GPS signal without obstructing its own ability to acquire PNT information.
China’s communications-satellite capabilities are considerably weaker than its reconnaissance and PNT capabilities. Currently, China has only two dedicated military communications satellites. By compar-ison, the U.S. military operates approximately 30 such satellites. State-owned corporations based in mainland China control another six or seven communications satellites, which could potentially be comman-deered for military purposes in the event of a crisis or conflict, but this would still provide China’s military with far less satellite communica-tions capability than the U.S. military possesses. China has the advan-tage, however, that for the foreseeable future, the conflicts in which it is likely to become involved would not entail the deployment of signifi-cant forces outside of mainland China. Forces operating in China can rely primarily on buried fiber-optic cables, which have far higher com-munications capacity, for communications connectivity. Buried fiber-optic cables are virtually impossible to jam and are difficult or impos-sible to find from the air or space, and their above-ground equipment, such as gateways, is easy to hide. Communications satellites occupy known, fixed locations and thus can be jammed, and their tracking and control stations are fixed and easily identified and thus potentially subject to attack. Because fiber-optic cable can carry many times more data than a satellite can, the commercial world has seen a de-emphasis of satellites relative to terrestrial cables (including undersea cables) in recent years. Satellite communications would be important primarily to naval forces at sea and ground forces deployed outside of China’s borders (e.g., on Taiwan). Given the still-incomplete process of link-ing China’s forces together using digital information links, moreover, China’s limited communications-satellite capacity may be sufficient for the immediate future, and this capacity will likely grow over time.
As noted earlier in this chapter, knowing and predicting weather can be crucial to successful military operations, but having one’s own weather satellites is not necessarily critical to this capability. China could rely on data from other countries’ civilian weather satellites. Having its own weather satellites, however, provides China with a hedge against a cutoff of such data in the event of a confrontation with the United Sates or other countries.
　
中國航空網(wǎng) www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：Ready for Takeoff China’s Advancing Aerospace Industry(70)