From the successful launch of the first test satellite of Beidou-1 in October 2000 to the launch of the last global networking satellite of Beidou-3 on June 23, 2020, in the past 20 years, 44 launches, China has successively sent 4 Beidou test satellites and 55 Beidou-2 and No. 3 networking satellites into space, opening up the era of China's "Star Network" navigating the world.
Recently, "Face to Face" interviewed Xie Jun, chief designer of the Beidou-3 navigation satellite, to tell the story behind the Beidou satellite.
Three years to overcome technical challenges
The launch was successful and there were only 2 hours left before the cut-off time
In 2004, the Beidou-2 satellite navigation system was officially established. Xie Jun, who has 22 years of work experience and has participated in the development of many major projects, has been appointed as the chief designer of the Beidou-2 satellite system. "From 2004 to 2007, it was probably the hardest time for me to be the chief teacher," he recalls. ”
The Beidou-2 satellite navigation system is based on Beidou-1, from the original only for China to expand to cover the Asia-Pacific region, requiring 14 satellites to support, while also overcoming some basic problems.
However, according to ITU regulations, the frequency resources and orbital position resources of navigation satellites are limited to 7 years from the filing date, and the overtime period does not need to be automatically invalidated. That means he and his team have only three years to solve the fundamental puzzle and get the satellite into space by April 17, 2007.
In the early morning of April 14, 2007, the first medium-circle orbit test satellite of the Beidou-2 system was successfully sent into space. But this is still a key move away from fulfilling ITU regulations.
Xie Jun: Not only must the satellite be sent up, but also the radio signal carried by the satellite must be transmitted to the ground and the signal must be received. Before the microwave components of the satellite go to the sky, they may carry some moisture on the ground, and before they are released, a microwave phenomenon may produce discharge, which will ablate the surface of the equipment and may affect the function of the product.
At 20:14 on April 16, 2007, Xie Jun made a decisive decision and ordered the power-up of the payload products on the test satellite. After 1 hour and 32 minutes, the navigation signal broadcast by the satellite was correctly received by the ground system, which is only 2 hours away from the ITU prescribed space frequency application expiration time.
Xie Jun said that this is a risky and successful decision, "I think there is a certain element of luck, we must have the courage to dare to take responsibility, but not simply blind, or a large number of ground experimental data support." ”
Imported atomic clocks could not be supplied on time
They produced China's own atomic clock
From the establishment of the project in 2004 to the completion of 2012, the positioning accuracy of the Beidou-2 satellite navigation system increased from 20 meters to 30 meters on Beidou-1, and improved to 10 meters for both horizontal and elevation, close to the GPS civilian standard at that time.
The improvement of positioning accuracy requires the support of a number of key technologies and components on the satellite, including the atomic clock known as the "heart of navigation satellites".
In 2006, due to the inability of imported atomic clocks to supply on time, the Beidou-2 construction project almost died, which deeply stung Xie Jun. He realized that as a space power, China must have an independent time-frequency reference system, which requires breaking through the technical difficulty of atomic clocks.
Xie Jun: When the project was established, I thought how could this thing be completed? When several of our units made atomic clocks on Beidou-2, it was very difficult, and often when the satellite generally needed to deliver atomic clocks, they were in a hurry, even rolling belts climbing, and could not be delivered on time.
At that time, the first on-board atomic clock product developed often had a sudden signal jump in the work, and the accuracy was very poor. Xie Jun's own profession is not the study of atomic clocks, he can only soak in the front line, and the experts who develop atomic clocks to analyze the problem together, find ways to overcome the difficulties, three years later, they crossed the threshold of atomic clocks.
The atomic clock timing accuracy currently used by the Beidou satellite is equivalent to an error of only 1 second in 3 million years, reaching the international first-class level.
"Contribute to the major projects of the country."
Be sure to do your job well."
After completing the construction of the Beidou-2 system, Xie Jun began to serve as the deputy chief designer of the Beidou-3 project and the chief chief designer of the Beidou-3 navigation satellite. During this period, Xie Jun worked continuously for a long time, fainted at the satellite launch site three times, and each time he woke up, he immediately rushed back to his post.
Xie Jun recalled, "One year Chinese New Year's Eve we were in the unit, everyone ate dumplings in the canteen, and no one was there after eating, so we immediately went back to test." ”
Xie Jun: That process did not feel easy, but everyone felt that they could contribute to the major projects of the country and must do their jobs well.
On June 23, 2020, the last networking satellite of Beidou-3 was successfully launched, and the Beidou global networking was completed. The localization rate of all single aircraft of the Beidou-3 satellite has increased from 80% to 100%, making China the third country in the world to have a global satellite navigation system after the United States and Russia.
At the same time, Xie Jun and his team launched the demonstration of the next generation of Beidou system construction and development system, began key technology research, and by 2035, they will design and build a national comprehensive timed navigation positioning system with the Beidou system as the core.
Xie Jun: Now it is basically the surface and the 1,000 kilometers above the surface so that users get a good navigation and positioning timing service, and the next system has to solve the higher space. From the accuracy of positioning, it is necessary to solve the centimeter-level navigation needs such as automatic driving that everyone is expecting now.
(Original title: Because of an incident, the construction work of Beidou No. 2 almost died, and he was deeply stung... ）
Source: CCTV News WeChat public number
Process Editor: TF060