[军事一瞥]美国防部未来十年缩小GPS服务

近日，美国政府责任办公室称将有可能在未来十年降低对GPS全球定位系统的使用。目前，该系统使用了包括24颗卫星在内的星座，在海拔约12，500英里处围绕地球旋转，虽然实际上运作的卫星约有31颗，但卫星的寿命很难估测。另外，考虑到未来的计划，管理等因素，政府责任办公室建议美国国防部未来降低GPS的使用。

GAO warns of threat to GPS service over the next decade

A major US government agency has predicted the possibility of serious problems for the Global Positioning System (GPS) （全球定位系统）over the next decade.

The Government Accountability Office (GAO政府责任办公室) reports that poor planning, ineffective management and lack of contractor oversight endemic（计划不全面，管理不力和承包监督流行） to US Department of Defense (DoD) space programmes could severely reduce worldwide GPS service between 2012 and 2018.

GPS employs a constellation of nominally 24 satellites that orbit the earth at an altitude of roughly 12,500 miles. Currently, there are 31 satellites in orbit, providing the best performance users have ever experienced, but that is unlikely to last, because each satellite's orbital life is unpredictable. Initially, they have a contractually promised design life of between seven and 12 years, depending on technology advances, and failures rarely occur within that period. In fact, most go well past that, with some remaining in orbit for 15 years.

Keke View：GPS术语
　　 Generalized Processor Sharing 通用处理器共享
　　 Global Positioning System 通用定位卫星／系统
　　3.[GPSS]General Purpose Systems Simulator通用系统模拟器
　　4.[DGPS]Differential GPS差分GPS,差分全球定位系统