What is the role of China in launching Beidou navigation satellite? Ask an expert to talk about it.

Beidou satellite positioning system is a regional navigation and positioning system established in China. The system consists of three Beidou positioning satellites (Beidou-1) (two working satellites and one backup satellite), and the ground part is mainly composed of ground control center and Beidou user terminal. Beidou positioning system can provide users with all-weather and 24-hour real-time positioning service, and the timing accuracy can reach tens of nanoseconds (ns), and the positioning accuracy is equivalent to that of GPS. Beidou-1 navigation and positioning satellite was developed by China Academy of Space Technology. The launch times of the three navigation and positioning satellites are: June 365438+1October 31,respectively, in 2000; 65438+February 2, 20001; On May 25th, 2003, the third satellite was a backup satellite. During the 2008 Beijing Olympic Games, together with the existing GPS satellite positioning system, it will play a "double insurance" role in the positioning and monitoring of traffic and venue safety.

The abbreviation of Beidou-1 satellite positioning system is BD, and the radio frequency bands registered in ITU are L-band (transmitting) and S-band (receiving). The English of Beidou second-generation satellite positioning system is Compass, and the radio frequency band registered in ITU is L-band.

The basic functions of Beidou-1 system include: positioning, communication (short message) and time service.

The function of Beidou II system is the same as GPS, that is, positioning and timing.

Edit the working principle of the system.

"Beidou-1" satellite positioning measures the distance between the user and the first satellite, and the sum of the distances between the user and the two satellites, thus knowing that the user is at the intersection of a sphere centered on the first satellite and an ellipsoid focused on the two satellites. In addition, the central control system can find the user's elevation value from the digital topographic map stored in the computer, and can know that the user is on an ellipsoid parallel to the earth reference ellipsoid. Therefore, the central control system can finally calculate the three-dimensional coordinates of the user's point, which is encrypted and sent to the user through the outbound signal.

"Beidou-1" covers the heart area between 5-55 north latitude and 70-140 east longitude, the largest part and the smallest part, and the widest part is around 35 north latitude. Its positioning accuracy is horizontal 100 m (1σ), and it is 20 m after setting the calibration station (similar to differential state). Working frequency: 249 1.75MHz system can accommodate 540,000 users per hour.

Compared with GPS system.

1. Coverage: Beidou navigation system is a regional navigation system covering China. The coverage is about 70- 140 east longitude and 5-55 north latitude. GPS is an all-weather navigation system covering the whole world. It can be guaranteed that 6-9 satellites can be observed anywhere on the earth at any time (in fact, at most 1 1 satellite can be observed).

2. Satellite number and orbital characteristics: Beidou navigation system sets two geosynchronous satellites on the equatorial plane of the earth, and the equatorial angular distance of each satellite is about 60. GPS will set 24 satellites on six orbital planes, with an equatorial inclination of 55 and an equatorial angular distance of 60. The satellite is in quasi-synchronous orbit, circling the earth once 1 1 hour and 58 minutes.

3. Positioning principle: Beidou navigation system is active two-way ranging two-dimensional navigation. The ground center control system solves the calculation of three-dimensional positioning data for users. GPS is passive pseudo-code one-way ranging three-dimensional navigation. The self-positioning solution independently solved by the user equipment is done there rather than by the user equipment. In order to make up for the fragility of this system, GPS is developing the technology of interstellar transverse data link, so that GPS satellites can operate independently when the main control station is destroyed. Beidou-1 system ruled out this possibility in principle. Once the central control system is damaged, the system cannot continue to work.

4. Real-time performance: The positioning application of Beidou-1 user should be transmitted back to the central control system, which will calculate the user's three-dimensional position data and then transmit it back to the user, during which it will go back and forth through the geostationary satellite once, plus satellite forwarding, the processing delay of the central control system will be longer, so the positioning error will be increased for high-speed moving objects. In addition, Beidou-1 satellite navigation system also has its own characteristics, and its short message communication function is not available in GPS.

To sum up, Beidou navigation system has the advantages of few satellites, low investment and simple and cheap user equipment, which can realize navigation and positioning, communication and other purposes in a certain area, and can meet the demand of navigation and positioning for land, sea and air traffic in China at present. The disadvantage is that it can't cover the polar regions, the positioning accuracy near the equator is poor, and it can only be actively positioned in two dimensions, and it needs to provide user elevation data, which can't meet the requirements of highly dynamic and confidential military users, and the number of users is limited to some extent. But the most important thing is that Beidou-1 navigation system is the initial starting system of satellite guidance independently established in China. In addition, the system does not rule out the wide application of GPS in the domestic civil market. On the contrary, China's GPS wide-area differential system will be established on this basis. The positioning accuracy of GPS civil code receiver interfered by SA can be revised from 100 meters to several meters, which can better promote the use of GPS in the people. Of course, we also need to realize that with the continuous development of our army's high-tech weapons, the information guarantee requirements for navigation and positioning are getting higher and higher. Beidou has improved the coordination of our army's precision guidance, positioning, strike, terminal sensitive bombs and troops for 20 years.