In November 2002, the then director of the National Astronomical Observatory AI Guoxiang put forward the basic idea of China's astronomical positioning system. Then he immediately organized experts from the National Time Service Center and the National Astronomical Observatory to demonstrate the theory. In 2003, the "China Area Positioning System" (CAPS) project was approved by the Chinese Academy of Sciences as a major knowledge innovation project.
Based on the long-term accumulation of time frequency technology and astronomical theory, CAPS, a new satellite navigation positioning method, based on GEO satellite platform, virtual satellite clock technology and transponder orbit determination technology was put forward innovatively. It has the characteristics of high-speed, saving and simplicity, and advancement.
CAPS uses the geostationary communication satellite and two or four tilt geosynchronous orbit satellite as navigation satellites, and its ranging signal and navigation message which transmitted to the user receiver by the satellite are generated from the ground without equipping with atomic clock. The coverage area is about 70 ° to 150 ° E and 10 ° to 60 ° N. The horizontal PN code ranging positioning accuracy is about 30 meters, and the height’s is about 100 meters, and unidirectional timing accuracy is better than 50 nanoseconds.
In December 2004, demonstration and verification of CAPS was completed. And then in May 2005, test and acceptance of CAPS was passed. The acceptance conclusion showed that the system which owns the advantages of advanced technology, low cost, short construction period and a broad prospect in application is an independent technology innovation in the field of satellite navigation.
Since the founding of People’s Republic of China, Chinese government has attached great importance to the work of time and frequency and the construction of national time service system. The Chinese Academy of Sciences, with the great help of departments in various fields, constructed BPM short wave time service system, BPL long wave time service system, BPC low frequency time-code time service system, network time service and telephone time service system, digital television time service system, and satellite time service system based on Chinese Area Positioning System (CAPS). The national time service system with all-aspect, multi-level and multi-means has been established which meets the needs of various industries and fields for different precision time and frequency.
