What is Beidou? Seven problems to understand the global navigation system of Beidou

 What is Beidou? Seven problems to understand the global navigation system of Beidou

30 satellites of beidou-3 system are distributed on three orbital planes. China Satellite Navigation System Management Office

One question: what is Beidou?

Generally speaking, beidou-3 system can be regarded as Chinese version of GPS.

Beidou satellite navigation system is built and operated independently by China focusing on national security and economic and social development. It can provide all-weather, all-weather, high-precision positioning, navigation and timing services for global users, and belongs to an important national space-time infrastructure.

Beidou has experienced three generations of development. Beidou No. 1 system was built at the end of 2000. It is a test system to provide services to China. From 2007 to 2012, Beidou II system was completed to provide services to the Asia Pacific region. From 2017 to 2020, the beidou-3 system, composed of 30 stars, was built, that is, the global navigation system, which can serve the world.

Beidou-3 is not a satellite, but a system, including 30 satellites. These satellites form a network that envelops the earth and its neighboring space. Therefore, the construction process of beidou-3 is also known as Networking.

MEO satellite is the main satellite of beidou-3, which operates in an orbit about 20000 kilometers away from the earth. It mainly provides navigation, positioning and time service, as well as global short message communication, international search and rescue and other special services. IGSO satellite mainly operates in an orbit of 36000 kilometers away from the earth. Because it is a high orbit satellite, it can effectively increase the number of satellites visible in the Asia Pacific region and provide better services for the Asia Pacific region. GEO Satellite mainly operates in the geostationary orbit 36 thousand kilometers away from the earth, providing regional short message, star based enhancement and other special services.

The constellation design of the three orbital surfaces is the original creation of the Beidou navigation system, and also has significant advantages. Compared with other navigation systems, the most prominent feature is the addition of high orbit satellites, the higher the anti occlusion ability of satellites, especially in low latitude areas. At the same time, with the use of high orbit satellites, Beidou has also added communication functions to provide global exclusive short message service.

Short message is a unique function of Beidou, which extends from Beidou No. 1 to Beidou No. 3 system.

In areas with mobile network coverage, this function seems to be a weak point, but in a large number of areas without network coverage, such as deserts, oceans, mountains, forests, etc., satellite communication must be relied on. Generally, satellite communication is more expensive, while Beidou short message is cheaper, and it is attached to the navigation terminal, which is more convenient, and it has been effectively applied in emergency rescue, pelagic fishery and other fields.

Today, the short message communication ability of beidou-3 is significantly improved, from 120 Chinese characters sent at a time to more than 1000 Chinese characters at a time, and it can also send information such as pictures, with more application scenarios.

In addition to short message, Beidou system has many special applications. Another example is international search and rescue.

The six MEO satellites of beidou-3 system are equipped with search and rescue payloads, which can provide search and rescue services for global users together with other global satellite search and rescue systems. For example, when a fishing boat is in distress in bad weather during its operation, the search and rescue terminal will automatically send the search and rescue signals to the satellite after touching the water. The satellite will transmit the information to the ground system. The ground system can quickly calculate the location of the people in distress and tell the rescue forces nearby to carry out the search and rescue work quickly. Lin Baojun, chief engineer of Beidou satellite system, previously introduced.

This service is a free public welfare service jointly carried out with other international satellite search and rescue systems according to international satellite standards, mainly used for the positioning and rescue of distress targets on water, land and air.

Xichang Satellite Launch Center will transport the long march 3B carrier rocket launched by the last networking satellite of beidou-3 to the launch area. First Academy of Aerospace Science and Technology Group


Four questions: Why build Beidou with GPS?

There are four global navigation systems built or under construction in the world. In addition to Beidou, there are GPS in the United States, GLONASS in Russia and Galileo in the European Union. GPS began to provide global services in the last century, and it has a large scale of application in China, but China has still made great efforts to build its own Beidou system.

For national defense security, navigation satellite is also particularly important. In the defense of national security, the guidance and navigation of many weapons and equipment are inseparable from satellite. Therefore, with GPS and other navigation systems, we still insist on building our own Beidou system, which is the strategic significance of Beidou.

5. How to use the service of Beidou?

For ordinary individual users, there is no need to choose a special way to use Beidou service. Beidou service has been built into our mobile phones, cars and other devices through chips. When we use navigation and positioning services, we have already used Beidou satellite.

Six questions: why can the Beidou system be built at a high speed?

Ran Chengqi, director of China satellite navigation system management office, said that Beidou system has fully borrowed, inherited and carried forward the unique management mode of China aerospace, and has also innovated many organizational management modes. For example, a global continuous monitoring and evaluation system has been established to monitor the operation of all satellite navigation systems, so as to improve the learning of Beidou system.

The launch rocket of Beidou satellite is a series of long triple a rockets, which are divided into three configurations: long triple A, long triple B and long triple C. Long triple a series is also the launch vehicle series with the largest number of launches and the strongest adaptability in China. At present, the number of launches is 112. Starting from the Beidou-1 system, 59 Beidou satellites have been launched 44 times by the Chang San Jia series, with a success rate of 100%.

In recent years, the long triple a series Rockets have been in the state of high-strength density launch, winning the first rocket model in the number of launches in China for five consecutive years. In order to launch 30 Beidou satellites in two-and-a-half years, the long 3A series Rockets have also been improved to meet the needs of three kinds of orbit launch.

The premise of launching a navigation satellite into the sky is to have legal orbit position and frequency resources, which are the precious resources that all countries in the world must contend for. On April 17, 2000, China won the orbit position and frequency resources in the International Telecommunication Union. According to the regulations, it is necessary to launch the satellite and receive the signal successfully within the 7-year validity period.

In fact, beidou-2 was set up in 2004, only three years. It is necessary to develop and successfully launch the first satellite, which generally takes five years. This star is not only the first satellite of the beidou-2 system, but also has the responsibility of launching the Beidou space orbit position and radio frequency.

The Beidou team worked day and night to enter the launch phase in early April 2007. At that time, the satellite had been integrated with the rocket and stood on the launch tower waiting for launch, but suddenly found that the transponder was abnormal. The researchers reopened the rocket fairing and checked the satellite.

Source: Qiao JunJing, editor in charge of Beijing News_ NBJ11279