A Positioning System based on Communication Satellites and the Chinese Area Positioning System (CAPS)
A Positioning System based on Communication Satellites and the Chinese Area Positioning System (CAPS)
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DOI：
10.1088/1009-9271/8/6/01
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发表时间：
2008-01-01
期刊：
影响因子：
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通讯作者：
Cai, Xian-De
中科院分区：
文献类型：
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作者：
Ai, Guo-Xiang;Shi, Hu-Li;Cai, Xian-De
中国区域定位系统（CAPS）是一种基于卫星通信的定位系统，它与3G（GPS、GLONASS和GALILEO）系统有着根本的不同。后者使用专用导航卫星向用户广播机载生成的导航信息，而CAPS则通过通信卫星向用户传送地面生成的导航信息。为了实现精确的定位、速度和时间（PVT），CAPS采用以下策略来克服使用通信卫星所带来的三个主要障碍：（a）通过实时跟踪稳频来实现频率稳定，（B）在36 MHz带宽的转发器中使用单载波来获得足够的功率，（b）通过在转发器中使用单载波来获得足够的功率，（c）通过在转发器中使用单载波来获得足够的功率，（d）通过在转发器中使用单载波来获得足够的功率。（c）结合已退役的地球静止轨道通信卫星、气压和倾斜地球静止轨道通信卫星，以达致立体定位。此外，DGEO上丰富的转发器可用于实现大容量通信以及导航通信一体化。通信功能的加入，使CAPS系统出现了5项新功能：（1）导航与通信相结合;（2）导航与高精度轨道测量相结合;（3）导航电文与广域/局域差分处理相结合;（4）卫星、频率、电码切换相结合;（5）导航电文与气压测高相结合。CAPS因此被标记为高精度PVT5C系统。为了验证CAPS的工作原理和性能，在两年的时间里建立了一个试验系统，耗资约2000万美元。试验星座由位于E87.5度和E110.5度的两颗GEO卫星、位于E130度和E142度的两颗DGEO卫星以及作为虚拟卫星的气压测高组成。完成了我国东、西、北方、南方和中部地区的静态和动态性能试验。评价结果如下：（1）陆地静态试验，平面精度范围：C/A码，15近似25 m; P码，5近似10 m;高度精度范围，1近似3 m;（2）陆地动态试验，平面精度范围：C/A码，15近似25 m; P码，8近似10 m;（3）速度精度，C/A码，0.13近似于0.3ms（-1），P码，0.15近似于0.17ms（-1）：（4）定时精度，C/A码，160ns，P码，13ns;（5）双向卫星时频比对（TWSTFT）的定时比对精度平均为0.068ns，（6）卫星测距的随机误差为10.7mm;（7）定轨精度，优于2米。上述随机误差为1 sigma误差。目前，该系统作为初步业务系统使用，正在建立一个包括3个地球同步轨道、3个地球同步发展轨道和3个地球同步观测卫星的完整系统。
The Chinese Area Positioning System (CAPS) is a positioning system based on satellite communication that is fundamentally different from the 3"G" (GPS, GLONASS and GALILEO) systems. The latter use special-purpose navigation satellites to broadcast navigation information generated on-board to users, while the CAPS transfers ground-generated navigation information to users via the communication satellite. In order to achieve accurate Positioning, Velocity and Time (PVT), the CAPS employs the following strategies to overcome the three main obstacles caused by using the communication satellite: (a) by real-time following-up frequency stabilization to achieve stable frequency; (b) by using a single carrier in the transponder with 36 MHz band-width to gain sufficient power; (c) by incorporating Decommissioned Geostationary Orbit communication satellite (DGEO), barometric pressure and Inclined Geostationary Orbit communication satellite (IGSO) to achieve the 3-D positioning. Furthermore, the abundant transponders available on DGEO can be used to realize the large capacity of communication as well as the integrated navigation and communication. With the communication functions incorporated, five new functions appear in the CAPS: (1) combination of navigation and communication; (2) combination of navigation and high accuracy orbit measurement; (3) combination of navigation message and wide/local area differential processing; (4) combination of the switching of satellites, frequencies and codes; and (5) combination of the navigation message and the barometric altimetry. The CAPS is thereby labelled a PVT5C system of high accuracy. In order to validate the working principle and the performance of the CAPS, a trial system was established in the course of two years at a cost of about 20 million dollars. The trial constellation consists of two GEO satellites located at E87.5 degrees and E110.5 degrees, two DGEOs located at E130 degrees and E142 degrees, as well as barometric altimetry as a virtual satellite. Static and dynamic performance tests were completed for the Eastern, the Western, the Northern, the Southern and the Middle regions of China. The evaluation results are as follows: (1) land static test, plane accuracy range: C/A code, 15 similar to 25 m; P code, 5 similar to 10 meters; altitude accuracy range, 1 similar to 3 m; (2) land dynamic test, plane accuracy range, C/A code, 15 similar to 25 m; P code, 8 similar to 10 m; (3) velocity accuracy, C/A code, 0.13 similar to 0.3 m s(-1), P code, 0.15 similar to 0.17 m s(-1); (4) timing accuracy, C/A code, 160 ns, P code, 13 ns; (5) timing compared accuracy of Two Way Satellite Time and Frequency Transfer (TWSTFT), average accuracy, 0.068 ns; (6) random error of the satellite ranging, 10.7 mm; (7) orbit determination accuracy, better than 2 m. The above stated random error is 1 sigma, error. At present, this system is used as a preliminary operational system and a complete system with 3 GEO, 3 DGEO and 3 IGSO is being established.