Beidou Satellite Navigation System: Take China's time and space information in your own hands

Our reporter He Liang and Fu Yifei

  "In 2020, the domestic output value of the Beidou system industry chain has exceeded 400 billion yuan, and overseas applications have accelerated, and have been applied in more than 120 countries and regions around the world..." On May 26, the 12th China Satellite Navigation Annual Conference Nanchang opened. When He Yubin, chairman of the China Satellite Navigation Commission, talked about the achievements of the Beidou system, the audience burst into applause.

  On July 31 last year, China solemnly declared to the world that China's self-constructed and independently operated global satellite navigation system was fully completed, opening a new chapter of high-quality services to the world and benefiting mankind.

  At this point, China's Beidou has officially stepped onto the world stage, standing in the "first echelon" of my country's active promotion of building a community with a shared future for mankind with practical actions.

  Out of the "Beidou Rhythm" in line with national conditions

  On the morning of June 23, 2020, in the hinterland of Daliang Mountain, the Long March launch vehicle lifted the 55th Beidou navigation satellite "Jixing" through the clouds and rushed into space.

With the "Gee Star" settling in the "big chess game" of the Beidou-3 network, all 30 Beidou-3 satellites have been put in place, and the constellation deployment has been fully completed.

  In November 1970, six months after the launch of the "Dongfanghong-1" satellite, China's first demonstration report on the development of a navigation satellite was completed.

At that time, a star-like navigation system had been made, with a vivid codename-"Lighthouse Project."

Although it was eventually terminated due to the transformation of technological direction and limited financial resources, it was like a beacon in the dark. With more than ten years of design and development, it has accumulated valuable engineering experience for the Beidou satellite.

  In 1983, experts and scholars represented by Academician Chen Fangyun proposed the idea of ​​using two geosynchronous orbiting satellites to determine ground and air targets.

After a lot of theoretical and technical research work, the concept of the "dual satellite positioning" system has gradually become clear.

  In fact, in order to verify the feasibility of "dual satellite positioning", Chen Fangyun led the research team at satellite measurement and control stations in Xinjiang, Guangxi, and Beijing, using the spare time of the two communication satellites between 0 and 2 midnight to conduct experiments.

A photo taken on September 25, 1989, records China's first successful demonstration of positioning using two satellites.

  At that time, there were still many factors to consider as to whether or not to start the expensive navigation satellite project immediately. The change in understanding occurred in 1990.

The Gulf War that shocked the world that year started under the gaze of the whole world. For the first time, the US GPS global satellite positioning system achieved great success in the form of weapon guidance. In the summary report, the Americans attributed the Gulf War to "GPS victory."

Both China and the world have felt the importance of owning navigation satellites from this modern war.

  In February 1994, a notice on the issuance of the project approval report for the double-star navigation and positioning system marked the official launch of the Beidou-1.

This year, the 65-year-old Sun Jiadong was appointed as the chief designer of the project.

  Prior to this, the United States and Russia both chose to directly build a global navigation system in one step.

However, the early Beidou engineering research funding, technical foundation, and talent team were very scarce, and China must find a new technological path.

With the deepening of practice and exploration, in the end, the idea of ​​"regional first, global second" was determined, and the "three-step" Beidou road was paved.

Academician Fan Benyao, the chief designer of the Beidou-1 satellite who participated in the discussion of the technical route, later commented: “Global networking requires a lot of time and money. At that time, users were still concentrated in China and the surrounding areas, so the technology of “region first, then global” The approach is more in line with China’s national conditions."

  Since 1994, Beidou-1 has gradually turned from a blueprint to a real satellite.

In October and December 2000, the two Beidou-1 satellites entered the predetermined orbits in space successively, which marked that China became the third country with a satellite navigation and positioning system after the United States and Russia.

  Beidou, which had just had its embryonic outline, soon made people understand its great value because of a special task.

On May 12, 2008, the shock waves of the Wenchuan earthquake circled the earth 6 times, and communications in Wenchuan, Yingxiu and other places were instantly interrupted.

A few hours later, a rescue team carrying the Beidou terminal transmitted the message through Beidou short message technology. Beidou became the only communication method in the earthquake area at that time, which greatly accelerated the efficiency of rescue.

  Beidou-1 has a short message function that other navigation systems do not have, precisely because the "double-star positioning" test in the 1980s was completed by communication satellites.

  Fight a beautiful "turn over"

  Due to the late start, when the Beidou-1 satellite took off, most of the 80% "golden navigation frequency band L-band" above the earth was already occupied by the United States and Russia.

  On April 17, 2000, China submitted an application for frequency bands to the International Telecommunication Union, and on June 5 of the same year, the EU Galileo satellite navigation system also submitted an application.

The International Telecommunication Union has approved a short frequency range for equal competition among countries. The rules for use are calculated from the date of application, and satellite launching and signal reception will be completed within 7 years. It is "first use, first served" and "abolished after the expiry date."

This means that Beidou-2, which has just started, must face a race against time.

  In 2005, the development and production of the Beidou-2 satellite has entered the most intense stage, but the domestic rubidium atomic clock that can be used by the satellite still has a gap with the actual demand.

  The on-board atomic clock provides time and frequency reference for navigation satellites. It is an important core component like the "heart", and it is the basis for determining satellite positioning and timing accuracy.

The plan was to introduce the core components of the on-board atomic clock from Europe, but the road to international cooperation has been repeatedly restricted.

This also strengthened the determination of Beidou people to insist on independent and controllable key technologies. Our country organized three units to tackle key problems at the same time, and finally conquered this key technology!

  On April 14, 2007, the first satellite of the Beidou-2 system equipped with the "Chinese Clock" was launched into space.

In order to preserve the frequency band, the satellite must transmit the signal back within 88 hours, and on-orbit debugging usually takes 7 days.

It was not until 8 o'clock in the evening on April 17 that the receiver interface suddenly bounced. After more than 80 hours after launch, Beidou-2 finally returned the first set of clear signals.

At this time, less than 4 hours have passed since the last time limit for the use of frequencies prescribed by the International Telecommunication Union.

China's Beidou squeezed into the global satellite navigation system club almost at the last moment when the door was about to be completely closed.

  At this point, Beidou, which was staggering but bravely moving forward, finally began to burst out a majestic force.

Beginning in November 2017, China has launched 30 Beidou-3 network stars and 2 Beidou-2 backup stars in 32 months with a 100% success rate, creating world navigation at an average rate of one star per month. A new record of satellite network launch.

  Today's Beidou-3 inherits and develops the hybrid constellation design with Beidou characteristics. It has the world's leading inter-satellite link and signal system. It is all equipped with domestic high-precision satellite-borne atomic clocks. The core components are 100% independently controllable and the satellite life is 10%. Over years, the positioning accuracy is better than 10 meters, and the timing accuracy is better than 20 nanoseconds. It can provide positioning, navigation, timing, satellite-based enhancement, ground-based enhancement, short message communication, precise single-point positioning, international search and rescue, etc.化服务.

  Let beautiful imagination become reality

  Beidou has formed a navigation constellation around the earth, composed of 30 Beidou-3 satellites, 15 Beidou-2 satellites, and many test satellites and backup satellites in orbit.

They fly in different altitudes and different angles of space orbits.

In people's daily life, scenes using Beidou navigation are almost everywhere.

  The transportation of gasoline and liquefied natural gas is extremely dangerous.

In my country, more than 400 million tons of dangerous goods are transported by road each year, which accounts for more than 30% of the total annual freight.

The terminal equipment based on Beidou navigation technology monitors the precise position of the vehicle and records the driving trajectory.

When the vehicle deviates from the scheduled route or appears abnormal, the monitoring center will issue an alarm in time.

The weather, road conditions, and operating status of the vehicle can be controlled, and even active intervention and intelligent control can be realized, effectively reducing potential hazards and accident hazards.

  At Shanghai Yangshan Deepwater Port, the newly launched "5G+L4 intelligent driving heavy truck" demonstration operation applied the Beidou system.

Its high-precision navigation and positioning enable heavy-duty trucks to park accurately at one time and automatically line up at short distances, improve the efficiency of Yangshan Port's intelligent transfer and the driving ability of Donghai Bridge, and let people feel the breath of the era of unmanned driving.

  The precise timing function of the Beidou satellite system allows the Chinese to take time, the law of material cycle changes, in their own hands.

  Each Beidou satellite is equipped with a high-precision atomic clock, which is timed by atomic transitions, which represents the ultimate human being's accurate time calculation.

At 6:10 am every day, the Beijing-Zhangjiakou high-speed rail EMU leaves the station on time.

This is China's first smart high-speed rail. Whether the departure, passing and arrival of the train are in line with the train schedule is a test of the precise control of time.

At a maximum speed of 350 kilometers per hour, based on Beidou time service, the Beijing-Zhangjiakou High-speed Railway realizes the time synchronization of operation, failure, communication and automation procedures. The Beidou all-in-one antenna that comes with the train can carry out information such as the time and position of the train. real time monitoring.

  Today, the Beidou system has fully served various industries such as transportation, public safety, disaster relief and mitigation, agriculture, forestry, animal husbandry and fishery, and urban governance. It has integrated into the construction of national core infrastructure such as electricity, finance, and communications. Deep integration of new technologies such as, artificial intelligence, etc., constantly turning beautiful imagination into reality.

  Build Beidou "Circle of Friends"

  From the perspective of all mankind, it is the bounden mission of China's Beidou to watch for peace and security and provide support and guarantee for the development of human society.

  In recent years, with the enhancement of service capabilities, the Beidou system has actively integrated into world affairs, performed international responsibilities, and has entered multiple international organization standards. The International Civil Aviation Organization has recognized Beidou as one of the four core constellations of the global satellite navigation system.

The first mobile communication international standard supporting the new global signal of Beidou-3 has been released. The first Beidou shipborne terminal detection standard has been announced to the world by the International Electrotechnical Commission. The International Maritime Organization has recognized Beidou system as a global radio navigation system. Develop standard documents and test network access to the search and rescue payload carried by Beidou-3...

  Since the 18th National Congress of the Communist Party of China, as a pioneer in the export of aerospace science and technology products, Beidou Systems has actively responded to the "Belt and Road" initiative to go abroad, providing customized services according to the different needs of different countries and industries, and gradually becoming a well-known "world brand." .

  In 2013, Myanmar used more than 500 high-precision Beidou terminals. This is the first time that Beidou high-precision products have been used in batches for agricultural data collection and land fine management in Southeast Asian countries.

In 2015, a high-precision receiver based on the Beidou system was applied to the construction of a 300-meter-high skyscraper at the headquarters of the National Bank of Kuwait, achieving millimeter-level measurement errors in the vertical direction during the construction process.

This is the first time Beidou has been applied to high-rise building monitoring overseas.

In 2018, Beidou System participated in the offshore piling project of Alahe Island in Maldives, providing all-weather, high-precision services, and realizing intelligent monitoring, visual operation and high-precision construction of offshore piling.

The Beidou system entered Russia, and the Siberian power line patrol realized the two-way interaction between on-site personnel and the management center, which can detect equipment defects and hidden dangers that endanger line safety in time, and ensure the safety of transmission and distribution lines and the stability of the power system.

The Beidou "drives" into Europe. On the China-Europe Express, the Beidou terminal is mounted on a container, which can record the trajectory of trains and goods in real time, with a positioning accuracy of less than 10 meters, and achieve seamless transfer throughout the entire track.

  In the new era, as a beautiful business card for our country, China Beidou will live up to its trust and make greater contributions to building a community with a shared future for mankind and promoting the development of human society.

  Today, the Beidou system has fully served various industries such as transportation, public safety, disaster relief and mitigation, agriculture, forestry, animal husbandry and fishery, and urban governance. It has integrated into the construction of national core infrastructure such as electricity, finance, and communications. Deep integration of new technologies such as, artificial intelligence, etc., constantly turning beautiful imagination into reality.