26 years development history of Beidou System: once stuck by Europe

 26 years development history of Beidou System: once stuck by Europe

On June 23, the 55th Beidou navigation satellite developed by the Fifth Academy of China Aerospace Science and Technology Corporation was successfully launched, and the deployment of beidou-3 global satellite navigation system Constellation was fully completed.

From the establishment of Beidou-1 system project in 1994 to the completion of the deployment of global satellite navigation constellation in 2020, Chinas Beidou has gone through an extraordinary 26 years.

It is of great significance to successfully complete the deployment of China beidou-3 global satellite navigation constellation. Pictures of this article, provided by No.5 and No.1 Aerospace Institutes

The first step of Beidou-1 is not smooth

Since ancient times, human beings have been thinking about a question: where are we? The ancients used the big dipper to navigate.

In October 1957, the first man-made satellite was launched. The sputnik-1 Soviet satellite officially kicked off the march of human beings into space and ushered in an era when human beings rely on satellites for navigation. In the process of observing the satellite, scientists of Hopkins Applied Physics Laboratory in the United States found the Doppler frequency shift effect caused by satellite motion, and asserted that it can be used to achieve satellite navigation. Then in the 1960s, the United States implemented the meridian instrument satellite navigation system, and achieved success.

When it comes to Chinas satellite navigation system, everyone will think of the well-known Beidou satellite navigation system. In fact, the Chinese idea of using artificial satellites for navigation and positioning was born in the 1960s, and put into practice, synchronized with the world. After the United States proposed the meridian instrument satellite navigation satellite, aerospace related units began to track and study satellite navigation technology. After the launch of Chinas first man-made satellite, dongfanghong-1, communication satellites, meteorological satellites, positioning and navigation satellites have all entered the field of vision of the decision-making level. At that time, the satellite navigation system was named lighthouse 1, but due to technological transformation, limited financial resources and other reasons, the plan was launched in the 1980s.

Lighthouse one is an early exploration of satellite navigation in our country. Lighthouse and Beidou have the same beauty. They both symbolize the guiding light that hangs high in the sky and never falls. In 1983, the experts and scholars represented by academician Chen Fangyun put forward the idea of using two geostationary orbit satellites to measure the ground and air targets. Through a lot of theoretical and technical research work, the concept of double star positioning system gradually became clear. The next Beidou road is a step-by-step global networking or a phased approach? At that time, there was a lot of controversy. Finally, the idea of first regional, then global was determined, and the three-step Beidou route was spread out.

Beidou-3 satellite

Todays Beidou has given a lot of gas to the Chinese people. But what many people dont know is that the first step of three steps in the construction of Beidou satellite navigation system, Beidou-1 system, is almost unable to move forward because of funds. In 1994, China was formulating the Ninth Five Year Plan for national economic and social development, and the relevant departments reported the Beidou project plan to the State Council. According to previous reports of China Aerospace news, Li Zuhong, former deputy chief designer of Beidou satellite navigation system engineering, said: at that time, including Beidou system, three satellite projects in China needed to be approved, and two other satellite projects had been approved. Due to the shortage of funds for satellite research, it is suggested that Beidou project should consider conducting pre research first, and the state should allocate a small amount of money to carry out pilot pre research. Lack of money was the biggest problem encountered by the Beidou-1 system at that time, and a small amount of state funding could not guarantee the completion of the project.

Looking at the Beidou No. 1 system project is likely to be stranded due to funding problems, the participating researchers are very anxious, and have held many meetings to discuss how to keep the Beidou No. 1 project. Under the national conditions at that time, the possibility of applying for project approval funds separately from the state was very low, and we could only find a way internally. Just in time, the other two satellite projects are respectively funded by the target of one backup satellite. After repeated consultations, we decided to take out the other two backup Star Funds and distribute them to Beidou No.1 Project, which solved the funding problem restricting the continued development of Beidou No.1 Project. Li Zuhong said.

After years of research and development, in 2000, with the successful launch of two geostationary orbit satellites, Beidou-1 system was built and put into use. With the active positioning system, it can provide positioning, time service and short message communication services for Chinese users. According to academician fan benyao, the chief designer of Beidou-1, the Fifth Academy of Aerospace Science and technology group, localization started from the solar sail of Beidou-1. At that time, many satellites were afraid to go up, and Beidou was the first one to eat crabs , which was hard on the head.. After that, the localization was even more difficult. No matter the emergence of Dongfanghong 3 platform or the key components affecting long life, with the spirit of self-reliance, the older generation of Beidou people represented by general director Li Zuhong and chief designer fan benyao conquered one by one. Finally, Beidou 1 system was built in 2003, making China the third owner after the United States and Russia Countries with autonomous satellite navigation systems.

Yang huizeng, former deputy chief designer of Beidou-1 and chief designer of beidou-2, said: although Beidou-1 system is a relatively primary satellite navigation system, we have explored the principle of satellite navigation system through this system to meet the basic needs of national defense and civil use, and laid some foundation for the further development of Beidou System in the future. For example, the third satellite launched in 2003 is not only an on orbit backup star, but also a test star for some technologies of beidou-2 system. Because this satellite carries some loads of beidou-2 system, it began to explore passive navigation technology.

Beidou-1 system played an important role in the 2008 Wenchuan earthquake relief. After the earthquake, the center equipped more than 1000 Beidou-1 terminals for the rescue forces, which realized the straight-line contact between each point and between the point and Beijing. In the case that the communication in the disaster area has not been completely repaired and the information transmission is not smooth, the rescue forces use Beidou-1 to send all kinds of information back in time and accurately, providing important information support for the headquarters to command the earthquake relief. The outstanding performance of Beidou-1 system has strengthened our countrys determination to develop more advanced satellite navigation system.

Beidou satellite is launched by long march 3A series rocket

Big Dipper two

After the successful establishment of Beidou-1 system based on the active positioning principle, Beidou system team began to turn their attention to the passive positioning satellite navigation system. Compared with the situation that Beidou No. 1 system encountered financial difficulties at the beginning of its establishment, Beidou No. 2 system has a much smoother financial situation. In August 2005, we reported on the project in Zhongnanhai, together with Change phase II and other high-profile space projects. Because Beidou system is not famous, we are the last in many projects to be approved. Unexpectedly, Beidou was the first one to be approved. When Yang Hui said these words, her tone was still a little surprised and pleased. This happened because there was so much consensus at that time that our country badly needed its own satellite navigation system.

Funding has not become a hindrance to Beidou II, but technical barriers have made it difficult for Beidou II to walk. The first is frequency. ITU has given S-band to navigation satellites, and the situation that there are too many pioneers, the United States and Russia, has seized many valuable frequency resources. When beidou-2 started, Galileo satellite navigation system, a powerful competitor, forced it to race against time.

ITU regulations: countries or organizations of frequency points of navigation can apply, the first one has the right of preferred use, and other countries or organizations can also apply, following the first come first served regulations. That is to say, everyone can apply, but whoever first launches the satellite and uses this frequency point, in order to prevent mutual interference, other countries or organizations cannot use this frequency point.

At first, ESA Galileo satellite navigation system and we all felt that it was necessary to cooperate. Later, we found that cooperation was conditional. We could not participate in the core payload part, just a user carrying the payload. Its not fair to pay for all this work. Yang Hui recalled.

In September 2004, the construction of Beidou II system was officially launched. On April 14, 2007, the first test star of beidou-2 was launched successfully. It took less than three years to send the test star into space, which is rare in space models. Yang Hui sighed: at that time, the satellite was in the initial stage, and many of the equipment was identification parts, not the exact samples for flight. When the satellite changes orbit and the load is fully open, it must race against time in order to occupy the frequency.

On April 16, 2007, two days after the successful launch, Beijing obtained a clear signal from the flight test star, which was less than four hours away from the failure of space frequency. This feat effectively protected the frequency resources of Chinas satellite navigation system and played an important role in the orderly promotion of Beidou regional navigation system construction.

Beidou team members test the satellite

At that time, the research and development work faced many difficulties: first, this is a multi satellite networking system, which must be produced in batches and launched intensively to ensure its effectiveness, but the production capacity and long life are great challenges; second, the navigation system must provide continuous and stable services, and the quality of any small part will affect the whole Beidou navigation constellation, causing service Service interruption, therefore, must guarantee zero defect; third, satellite system adopts many new technologies, new devices and new processes, which makes it difficult to tackle key problems; fourth, the research and development team is very young, lacking necessary system knowledge and engineering experience.

Among these problems, it is the most difficult to develop a domestic rubidium clock. The research and development of rubidium clock on board is full of drama. At that time, China was ready to import from Europe and signed a contract with the European company that produced the rubidium clock on board. However, the other party has put forward a precondition, that is, it must obtain the sales license issued by the Swiss government to China. As for when and whether to obtain the license, the other party will not make any commitment. This event affected the research and development progress of Beidou system 2. As the chief designer of beidou-2, Xie Junbi knows that if the rubidium clock on board cannot be made, the positioning accuracy and R & D process determined by the engineering task cannot be guaranteed. After the launch of the research and development of the onboard rubidium clock, through the full efforts of the research and development team, the independently developed onboard rubidium clock was finally born, which filled in the domestic gap, and its indicators were even better than those of foreign products. In Xies view, the only way to overcome this difficulty is to persevere.

There have been some setbacks in the development of Beidou navigation satellite.

In Yang Huis memory, the most difficult time in the R & D process is when he encountered a fault. Because the fault data is only a few seconds, its very difficult to find out the location and cause of the fault through these seconds.

Beidou team members report the progress of finding problems to experts and peers in the daytime, and find problems overnight. After a week of continuous work, they lie on the table for a while when they are sleepy, and finally the problems reappear on the ground.

There was a lot of pressure at that time, and the whole team fell into a low ebb, because we secretly ran against Galileos system, and the result of the satellites problems was that the process was delayed, Yang Hui recalled. That time can be described as hardship. This kind of hardship is not only the intense work and frequent overtime work, but also to withstand all kinds of pressures and complete the important tasks assigned by the state on time with high quality. At that time, we had to always warn ourselves that we must not give up, let alone give up. This is the task of our country. We can only insist on it.

Since 2009, Beidou system has embarked on a new journey - starting the construction of Beidou global satellite navigation system, the research and development team has started to tackle the relevant technical problems of the global system.

On January 17, 2010, the first formally networked Beidou navigation satellite was successfully launched. On October 25, 2012, the 16th navigation satellite was launched, which was networked with the 15 Beidou navigation satellites launched in advance, forming a regional service capacity. In just a few years, more than ten navigation satellites have been launched, which not only creates a single model of intensive delivery and launch record in China, but also rarely seen in the world.

Group photo of Beidou team

Beidou takes the third step with great confidence

Just before beidou-2 officially provided regional navigation and positioning services, the demonstration and verification of beidou-3 global navigation system started, and the development requirements were clarified, and the development goal of building an independent, open and compatible, technologically advanced, stable and reliable global satellite navigation system was determined. Since then, Beidou has taken the lead and started a new journey from innovation and development.

Building a high-performance and reliable Beidou global satellite navigation system is one of the 16 major projects in the medium and long-term development plan of Chinas science and technology field. The system construction is not only the improvement and upgrading of Beidou regional system, but also the climbing and leaping of the world-class satellite navigation system. After the completion of the system, its performance is equivalent to that of GPS, which will make Chinas satellite navigation system reach the international advanced level.

Compared with Beidou No.2 regional system, Beidou No.3 service area will be expanded to the whole world. At the same time, it has achieved breakthroughs in key technologies such as upgrading and transformation of the downlink navigation signal, realized the smooth transition with Beidou No.2 downlink navigation signal, and added new navigation signals on this basis to provide users with better services.

Standing on the shoulders of the previous two generations of constellations, Beidous third step is extremely confident. Under the leadership of Xie Jun, Chi Jun, Wang Ping, Chen Zhonggui and other experts, the R & D team of the Fifth Academy of Aerospace Science and Technology Group has gathered all forces to regard the workshop as a battlefield, and the key problem as a battle, and worked hard to overcome various difficulties of the Beidou system.

In December 2019, the deployment of beidou-3 global core constellation was completed

Because Chinas Beidou system cant establish a ground station in the world like the U.S. GPS, in order to solve the data transmission channel of overseas satellites, Beidou No.3 research and development team of the Fifth Academy of Aerospace Science and Technology Group conquered the link technology between constellations and satellites, adopted the integration design of inter satellite and satellite ground transmission functions, and realized the link interconnection between satellites, satellites and ground stations. The technology of inter satellite link not only realizes the communication and data transmission between each other, but also ranges the distance between each other, automatically keeps the formation, which can reduce the pressure of ground management and maintenance. In the application of inter satellite link technology, a new network protocol, management strategy and routing strategy are designed to solve the problem that the satellite can not be deployed globally for overseas monitoring, which is a major feature of the construction of Beidou global navigation system.

In order to improve the service accuracy, beidou-3 is equipped with a new generation of atomic clock, which can improve the satellite performance and user experience by improving the atomic clock index. Atomic clock is to ensure the accuracy of the generation time by using the characteristics of stable atomic transition frequency. At present, there are mainly rubidium atomic clock, hydrogen atomic clock and cesium atomic clock in the world. Chinas Beidou satellite adopts rubidium atomic clock and a new hydrogen atomic clock with higher performance. Although the mass and power consumption of hydrogen atomic clock are larger than rubidium atomic clock, its stability and drift rate are better.

Compared with rubidium atomic clock, China started later. In 2015, the hydrogen atomic clock developed in China was first verified in orbit, which explored the technology of Beidou global navigation system, and its function and performance are very stable up to now. The application of hydrogen atomic clock in orbit plays an important role in the navigation and positioning of Beidou.

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