Beidou satellite navigation system performance by leaps and bounds and positioning precision level m

Yang changfeng, a member of the national committee of the Chinese people's political consultative conference (CPPCC) and chief designer of the beidou satellite navigation system, told the media recently that the six beidou 3 satellites were launched in succession to form a network, which is used to verify the basic framework of the global network of the beidou satellite navigation system. The six satellites include the 28 and 29 beidou navigation satellites launched on February 12. And that's just the beginning of the big drama of the 2018 BDS.

According to the CPPCC national committee, China aerospace science and technology group five yuan (hereinafter referred to as the five yuan) Zhao Xiaojin introduction, the party secretary of beidou no. 3, 2018 planned launch 10 times, a total of 18 satellite launch, for "neighbourhood" all the way along the countries and regions to provide basic services, and complete more than 30 to 2020 satellite network, achieving global services lay a key foundation. In the future, China will build a national integrated navigation, positioning and timing system with the beidou system as the core, which will form a complete system in the sky, ground, underwater and indoor environment and significantly improve the country's spatio-temporal information service capacity.

Beidou GPS comparable to only a few stars

As one of the 16 major projects of China's medium - and long-term development plan in the field of science and technology, the construction of a high-performance and highly reliable beidou global satellite navigation system is not only a perfect and upgrade of the beidou regional system, but also a climb aimed at the world's first-class satellite navigation system.

According to xie jun, deputy chief designer of the beidou-3 project of the fifth academy and chief chief designer of the satellite, compared with the bds-2 regional system, the bds-3 has achieved a number of key technological breakthroughs and can provide users with better services. When the system is completed, its performance will be comparable to that of GPS.

It is impossible for beidou to establish ground observation and control stations like GPS. In order to solve the problem of overseas satellite data transmission, the research team adopted the integrated design of satellite to satellite and satellite to ground transmission function, and realized the link intercommunication between satellites, satellites and ground stations. Even if the earth station cannot directly contact the beidou satellite flying on the other side of the earth, the data transmission can be realized through the communication between satellites. At the same time, the inter-satellite link technology can also make beidou satellites distance each other, automatically "maintain formation" and reduce the pressure of ground management and maintenance through new network protocol, management strategy and routing strategy.

The reliability and continuity of satellite navigation system are facing severe requirements. Once the service is interrupted, the normal operation of the country and society will be greatly affected. According to chi jun, chief commander of the beidou-3 satellite of the fifth academy, the satellite is capable of operating independently for more than 60 days, and will be able to work normally in orbit even if the ground station breaks down. At the same time, the satellite with a number of reliability measures, with fault self-diagnosis, repair ability, design life of more than 10 years.

The on-board atomic clock is the key equipment to ensure the accuracy of navigation. The bds-3 satellite is equipped with a new generation of rubidium atomic clock developed by xi 'an branch of the fifth academy. Its frequency stability is 10 times higher than that of the bds-2 system, reaching the world's advanced level. This will enable the positioning accuracy of the beidou navigation system to span from 10 meters to meters, and the speed measurement and timing accuracy to be improved by one order of magnitude simultaneously. At the same time, the bds-3 satellite will also be equipped with a new hydrogen atom clock developed by no.203 institute of the second academy of China aerospace science and industry corporation. Its mass and power consumption are larger than those of the rubidium atomic clock, but its stability and drift rate are better. Two kinds of atomic clocks are used together to help guide the beidou.

From "lofty" to "grounding" popular applications at your fingertips

, director of the China satellite navigation system management office, RanCheng its December 2017 in the scio conference, big dipper and the Internet, cloud computing, big data fusion, built high precision time and space information of cloud services platform, launched the world's first support the acceleration of beidou auxiliary positioning system service covers more than 200 countries and regions, users reached 100 million, 200 million day service.

At present, the BDS has formed a relatively complete industrial system including basic products, application terminals and operation services.

Through beidou industry demonstration, satellite navigation and various sectors of the national economy have achieved a deep integration: 4.8 million operating vehicles in China have installed beidou compatible terminals, forming the world's largest beidou vehicle network platform, effectively enhancing the monitoring efficiency of road operating vehicles and improving the level of road transport safety. According to data released by the ministry of transport, the major accident rate and casualty rate of road transport in 2016 were respectively down by about 50% compared with 2012. In addition, more than 40,000 fishing boats across the country were equipped with beidou, helping tens of thousands of fishermen. With the help of the beidou system, the reporting time of sudden major disasters is shortened to less than 1 hour, and the response efficiency of emergency rescue is increased by 2 times. Beidou-based high-precision services have been used in precision agriculture, dilapidated housing monitoring, unmanned driving and other fields.

Not only that, "in the past five years, beidou has changed from 'lofty' to 'down-to-earth'." Mr. Ranchengqi said mass applications of the system are also within reach. Most of the world's mainstream mobile phone chips support beidou, which is becoming the standard in China. In Beijing, more than 30,000 taxis and 20,000 buses have been installed. 1500 logistics trucks and 19,000 deliverymen use beidou terminal and mobile phone to access the logistics cloud platform to achieve real-time scheduling. Sharing bicycle equipped with beidou to achieve fine management; The watches, bracelets and student CARDS that support beidou are more convenient for People's Daily life.

We should be both China's and the world's beidou

In early December 2017, China and the United States signed the joint statement on beidou's compatibility and interoperability with GPS signals (the statement). Lu xiaochun, deputy director of the national timing center of the Chinese academy of sciences, said the signing of the agreement is of historic significance and will bring better and more convenient services to users.

The statement pointed out that beidou satellite navigation system and GPS global satellite navigation system have achieved radio frequency compatibility under the itu framework, and the two systems have achieved mutual operation of civilian signals B1C and L1C. Users can use both beidou and GPS civilian signals, and enjoy better services without significantly increasing costs.

According to the working principle of the satellite navigation system, the receiver needs to "see" at least four navigation satellites at the same time to realize positioning, lu said. If a single navigation system is used, there may be a limited number of satellites over a certain area with insufficient redundancy. Once the receiver is disconnected from a satellite, the continuity of positioning service will be affected. When beidou and GPS achieve mutual operation, it is equivalent to integrating the navigation system which used to be independent. Users use a receiver to receive satellite signals from two systems at the same time. There are not enough GPS satellites, and there are beidou satellites, so the stability and accuracy of positioning will be higher.

In today's world, the four major satellite navigation systems -- GPS, beidou, glonas and Galileo -- compete for glory. If all of them are completed, there will be more than 100 global navigation satellites. The BDS has always adhered to the concept of "China's BDS and the world's BDS", and should be mutually compatible with other satellite navigation systems for common development, so as to benefit "one family" globally.

Under the guidance of this principle, BDS has designed a compatible and interoperable technology, which provides a basis for users to receive multiple signals on the terminal, and the resulting convenience will ensure the maximization of global users' interests.

Ran chengqi said that China has continuously promoted the internationalization of the BDS over the years, actively and pragmatically carried out international exchanges and cooperation. Among them, China and the United States will carry out new BDS global signal compatibility and interoperability coordination, and promote cooperation in enhancing systems and civil aviation applications, civil services and monitoring and evaluation. In November 2016, China and Russia launched seven cooperation projects, including the satellite navigation monitoring and evaluation service platform, the beidou and glonas cross-border transport vehicle joint application demonstration, and the satellite navigation chip joint design center. New cooperation in satellite-based enhanced systems and education and training programs in satellite navigation are being promoted. China and the eu have completed the first round of frequency coordination of the navigation frequency bands of the BDS and Galileo systems, and established a mechanism for exchanges and cooperation in areas such as compatibility and interoperability. In addition, China has actively promoted the BDS's entry into relevant standards of international civil aviation, international maritime affairs, mobile communications and other international organizations, and has extensively participated in the activities of international satellite navigation organizations.

Now, China's BDS has opened its mind and is waiting for the world to accept it.