Xie Jun, "Beidou Man": We are practical space dreamers looking up at the stars

　　 Xie Jun, Deputy Chief Designer of Beidou-3 Project of the Fifth Academy of Aerospace Science and Technology Group, and Chief Chief Designer of Satellite. Photographed by Li Chuan, reporter of China Youth Network

Looking up at the stars, we can see two "Big Dippers". One has 7 stars, which have existed in the universe for hundreds of millions of years, and has been pointing for human beings since ancient times; One star has 30 stars, which have been born and developed from scratch for only 26 years. However, it can provide humans with a positioning accuracy of 10 meters in the vast space.

The former is called "Big Dipper", which is a gift from nature; The latter, called "Beidou-3 Global Navigation Satellite System", is a miracle created by Chinese astronauts.

As the deputy chief designer of Beidou-3 project of the Fifth Academy of Aerospace Science and Technology Group and the chief designer of satellite, Xie Jun always has many feelings when talking about this.

In 1982, Xie Jun graduated from the National University of Defense Technology and was assigned to work in 504 institutes of the Fifth Academy of China Aerospace Science and Technology Corporation, where he embarked on the road of aerospace.

Draw a blueprint to the end. In 1983, Chen Fangyun, an academician of the Chinese Academy of Sciences, put forward the idea of using two geosynchronous orbit satellites for positioning and navigation, that is, the idea of double star positioning, which started a great journey like pioneering.

In 1994, the construction of the Beidou-1 satellite system project was officially launched. In 2000, two Beidou-1 satellites were successfully launched, making China the third country in the world to have an independent satellite navigation system. Beidou-1 system adopts active positioning system, which can provide positioning, time service and short message communication services for Chinese users. The system design and construction conforms to the national conditions of China at that time, and fully embodies the principle of "fast, good and provincial".

In 2004, when the Beidou-2 satellite system project was officially launched, Xie Jun also officially took the post of chief designer of Beidou-2 navigation satellite. For Xie Jun, this is a new post, which also means a new mission and responsibility.

Compared with Beidou 1, Beidou 2 system should be compatible with the technical system of Beidou 1 system, and add a passive location system to provide location, speed measurement, time service and short message communication services for users in the Asia Pacific region.

Xie Jun said frankly that although the R&D road was full of difficulties and thorns, he and his team never gave up, and always overcame difficulties and went against the current.

In Xie Jun's memory, 2007 is an important node of Beidou-2. "In order to ensure the precious frequency resources applied for domestically, we overcame difficulties and successfully launched the first navigation satellite of Beidou-2 on April 14," Xie Jun said.

The success of the first battle also officially kicked off the construction of Beidou-2 networking.

Since then, Beidou-2 has entered the fast lane of network construction. In 2010, five Beidou-2 satellites were successfully launched; In April 2011, the "3GEO+3IGSO" basic system was built; In December 2012, 14 satellites were officially networked and operated, and Beidou-2 system provided official operation services.

Xie Jun said that by 2019, China had successfully launched 20 Beidou-2 satellites, marking a unique path for the development of satellite navigation systems. "This is a unique hybrid constellation system, and the accuracy of the Asia Pacific region has reached the international advanced level."

"The hybrid constellation system has obvious advantages, which is to use high orbit satellites to provide services to some regions, and at the same time, the medium circular orbit satellites provide services to the world," Xie Jun said.

Every step is sonorous and forceful.

In 2009, when the construction of Beidou II was in full swing, the construction of Beidou III system was launched. Xie Jun believes that this is a key step for the Beidou system to become a world-class and comprehensive GPS system.

"The satellite can't move freely in the sky. A move is equivalent to a change in coordinate values. It needs precise control and measurement, which involves the key device atomic clock." Xie Jun said that high-precision atomic clock is crucial for the Beidou navigation satellite.

At the beginning, the atomic clock used on the Beidou navigation satellite depended on imports, which was both restricted by people and could not fully guarantee the quality, affecting navigation services.

Time accuracy is the lifeblood of satellite navigation. The more synchronized the time between the sky and the earth, the smaller the error, the higher the positioning accuracy. After careful consideration, Xie Jun is determined to make the on-board atomic clock 100% localized and take the road of independent research and development, "we must firmly grasp the important core and key technologies in our own hands".

Once you have set your mind, no matter how hard it is, you should rise to the challenge and speed up.

If the road is long and obstructed, you will arrive when you travel. Xie Jun said frankly that the development of spaceborne atomic clocks is very difficult.

The rubidium atomic clock applied to the Beidou navigation satellite excites rubidium atoms in rubidium bulbs to move back and forth through microwave fields to generate a fixed frequency. The emitted frequency enters the absorption bubble after filtering out the unstable noise through the light filter bubble, and finally generates a light detection signal through the photoelectric detector.

"High precision time and frequency signals determine the time service accuracy between satellites and ground, and atomic clocks have very high requirements for space environment," Xie Jun said.

In order to achieve the ideal use effect on the satellite, Xie Jun led the research and development team to carry out research and test. They specially designed a temperature control cabin on the whole satellite to ensure the space temperature environment of the atomic clock with high temperature control accuracy.

Sometimes, in order to solve a problem, team members will fight with each other, and even if they return to zero, they will have to go back to the problem.

It is in this rigorous and meticulous development process that China's self-developed rubidium atomic clock was installed on the Beidou navigation satellite.

Xie Jun said that from the "imagination" that still existed in the drawings in 2004 to the high precision products that are now widely used in Beidou navigation satellites, it is not easy to walk this way in retrospect, but the process is a profound reflection of the spirit of Beidou in the new era.

Independent innovation, openness and integration, solidarity and pursuit of excellence are the Beidou spirit in the new era.

It is the first time to win the "frequency", overcome the difficulty of "no clock", eliminate the worry of missing "core", and solve the difficulty of "station" distribution. Today, China's Beidou navigation system has reached the world-class level, with less than 80% localization on Beidou-2 satellite and 100% localization on Beidou-3 satellite.

Xie Jun said, "We promise to provide navigation better than 10 meters worldwide. According to the measured results, the horizontal positioning accuracy reaches 1.6 meters, the elevation positioning accuracy reaches 4.4 meters, and the key areas are even more accurate, with the timing accuracy of 10 nanoseconds."

In Xie Jun's view, this is the most incisive embodiment of independent innovation and the pursuit of excellence.

June 23 this year is an important day that Xie Jun cannot forget in his aerospace career.

In the early morning of that day, Xie Jun stood in front of the launch tower of Xichang Satellite Launch Site and looked at the Long March 3B carrier rocket in front of him, feeling both excited and calm.

At 9:43 that day, the 55th navigation satellite of the Beidou system and the last global networking satellite of the Beidou-3 were launched and flew into space.

27 minutes after the launch of the satellite, the separation of the satellite and the arrow was completed, and the solar wings on both sides of the satellite were successfully extended. At that moment, Xie Jun's strained heart finally relaxed.

Xie Jun said that the end of the Beidou satellite navigation system is a milestone for generations of spacemen and Beidou people to finally achieve their goal of traveling in space.

On July 31, the completion and opening ceremony of the Beidou-3 global satellite navigation system was held in the Great Hall of the People. At 10:48, General Secretary Xi Jinping took the podium and announced that "the Beidou-3 global satellite navigation system was officially launched!".

General Secretary Xi Jinping fully affirmed the achievements made in the construction of the Beidou system, especially the Beidou-3 global satellite navigation system. He pointed out that the completion and opening of the Beidou-3 global satellite navigation system fully reflected the political advantage of China's socialist system in concentrating its efforts on major issues, and it would help to enhance China's comprehensive national strength, promote China's economic development and improve people's livelihood under the conditions of normalization of epidemic prevention and control, promote China's opening up to the outside world under the current international economic situation, and further enhance national self-confidence It is of great significance to strive to achieve the "two centenary goals". Over the past 26 years, all personnel involved in the development and construction of the Beidou system have risen to the challenge, fought hard and continued to struggle, carried forward the spirit of "two bombs and one star", and cultivated the Beidou spirit of the new era, which should be well inherited and carried forward. We should promote the application of the Beidou system, do a good job in ensuring the stable operation of the system and other follow-up work, and make new and greater contributions to promoting China's economic and social development and building a community with a shared future for mankind.

Looking up at the starry sky, there is the dream of Chinese spacemen. General Secretary Xi Jinping once said, "Exploring the vast universe, developing the aerospace industry and building a powerful aerospace country are our unremitting pursuit of the aerospace dream."

For Xie Jun, the Beidou satellite navigation system is an important embodiment and an important station to realize China's space dream. On the 38 year spaceflight road and the 16 year Beidou road, Xie Jun sighed most about the long road ahead, the honorable efforts of countless spacemen, and the indifference and confidence in looking back today.

On this road, in the spring, summer, autumn and winter of 26 years, more than 400 units and more than 300000 scientific research personnel worked together to integrate themselves into the huge project of China's Beidou cause, regardless of the individual, to achieve the big one.

"Our journey is a sea of stars." Xie Jun said that today, more young Beidou people have become the main force in this journey. They are more energetic, more energetic, and more enthusiastic and hopeful about the dream of becoming a powerful aerospace country. (China Youth Network reporter Li Chuan)