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

Two and a half years, 30 satellites, the largest satellite system in China with the widest coverage and the highest performance requirements, what is it? Here are 7 questions for you to understand.

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.

Second question: what kind of net has Beidou set up?

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.

The 30 satellites on this network are distributed in three different altitude orbit planes, including 24 MEO satellites (earth medium circle orbit satellites), 3 IGSO satellites (tilt geosynchronous orbit satellites) and 3 geo satellites (geostationary orbit satellites).

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.

Navigation satellite and communication satellite are two kinds of satellites, but Beidou navigation satellite has additional communication function. Wang Bo, deputy secretary-general of China satellite navigation and positioning Association, said that Beidou users can not only know their own location, but also tell others their own situation through short message by using the terminal.

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

Xie Jun, chief designer of beidou-3 satellite project, said that satellite navigation system is an important space infrastructure of a country, even the support and foundation of infrastructure. If we use foreign key technologies to purchase foreign core products, once they are out of stock, the system will not be able to run stably for a long time.

Wang Bo said that in many important industries of national economy and peoples livelihood, the space-time benchmark provided by navigation system is indispensable. Precise time and space benchmark can be said to be a countrys strategic resources. Industries such as communication, power grid and finance all need precise positioning and timing functions of navigation satellites.

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.

Yang Changfeng, chief designer of Beidou satellite navigation system engineering, previously introduced that 70% of Chinas new smartphones have built-in Beidou chips, or Beidou and GPS dual-mode chips. The dual-mode chip can use GPS and Beidou system at the same time. This kind of use is not either or, but uses Beidou and GPS satellites at the same time. The chip will automatically select the navigation satellite signals that can be received at present, which may come from the combination of Beidou satellite and GPS satellite. Through four or more satellites, the current position can be calculated.

Beidou has also been widely used in transportation, agriculture, forestry and fishery, disaster reduction and relief and other industries. It can be realized through some terminal equipment with Beidou chip in it.

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

The construction of beidou-3 is called speed. From the launch of the first star on November 5, 2017 to the end of the official period on June 23, 2020, 30 star networks have been completed in just two years and seven months, during which, two beidou-2 satellites have been launched, improving the constellation of beidou-2.

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.

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.

According to China Academy of launch vehicle technology, the long triple a series of rockets also have the ability to launch large satellites from two satellites, long-time taxiing at the last stage, narrow window / multi window or even zero window launch, and the ability to delay the launch for another 24 hours after low-temperature propellant filling, which ensures that the long triple a series can meet the needs of most payloads.

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.

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.

Yang Changfeng said that foreign technology blockade has become the biggest bottleneck restricting the construction of Beidou satellite navigation system. For example, in the early stage of the development of beidou-2, it was intended to introduce the core device component, the atomic clock, from abroad, but due to foreign reasons, it failed to cooperate. But in just two years, Chinese researchers have overcome the biggest technical bottleneck of the atomic clock. Today, the accuracy of the Beidou systems atomic clock has been improved to one second less than every 3 million years.

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