Beidou "Net Collection": 26 Years From Catching Up To Surpassing

In June 23rd, every move of the Xichang satellite launch center was tied up by hundreds of millions of people.

At 9:42 in the morning, the long march three launch vehicle was powered by itself. At 9:43, the rocket was officially launched and the booster was separated. At 10:09, the stars and arrows were separated. At 10:15, Zhang Xueyu, director of the Xichang satellite launch center, confirmed that the fifty-fifth Beidou navigation satellite launched successfully. This has become a historic moment for China's satellite navigation system.

With the success of the last geostationary orbit satellite (GEO), Beidou three global satellite navigation system has completed the global networking. Since then, a group of satellites that have been independently developed by China have been able to cover the global sources of signals and form a "constellation" sea. To achieve this goal, our country has only walked for more than twenty years.

When it comes to navigation, the closest thing to the public is probably mobile phones. A familiar scene is the hint of "weak GPS signal" in the map software. Although it has hit the name of the US global navigation satellite system GPS, in fact, the GPS used in the mobile phone today is the abbreviation of the global positioning system. It is the product of the comprehensive judgement of the four major satellite navigation systems in the world.

In addition to the Chinese Beidou and the US GPS, the core suppliers of the global satellite navigation system (GNSS) are the European Union Galileo and the Russian GLONASS. Based on their respective development processes, deployment of technology placement and spectrum resource differences, the multi-layer large scale network has been co developed at the altitude of the earth's atmosphere. The four systems are compatible with each other and provide a high-precision satellite navigation service for mankind.

In contrast, China's Beidou system started late, but it has an original medium and high orbit hybrid constellation architecture, and has unique function settings in obtaining location information. In a meeting at the end of 2019, Ran Chengqi, director of China's satellite navigation system management office, said, "the Beidou three system we built is entirely independent innovation, independent design, independent construction and independent control. It is a Chinese created product."

But this is far from the end. According to Cao Chong, chief scientist of China satellite navigation and positioning Association, in the next ten years, satellite navigation technology still needs to be overcome, and the wider application market is still limited by human imagination.

The deployment of the next four generation of satellite navigation systems for the next generation of technologies and services has long been open, and it has been selected as a new node around 2035.

Three steps in 26 years

As early as the 70s of last century, our country has proposed the establishment of its own satellite navigation and positioning system -- lighthouse system. According to Li Changjiang, commander in chief of the Beidou two satellite system, because of the lack of support of the national economy at that time, the system finally left the stage of history.

Over the next period of time, China used GPS navigation technology in the United States for many times. But these channels, which represent the precise positioning of personal time and space, are held in the hands of others. It is not only related to the control of independent security, but also faced with the dilemma of "being choking" after a certain historical stage.

The key starting point took place in 1994. After the subjective and objective conditions were relatively mature, China was determined to start the construction of the Beidou satellite navigation system.

This is a process from scratch, but the appeal is becoming more urgent. In that year, the US GPS satellite navigation system was built and put into operation. From the historical nodes, they ran ahead of us and became the most mature satellite navigation system in the world for a long time.

For the early days of China's Beidou, from technical terms to financial support, many are unknown. But China's satellite technology system has sprung up talents, laying the foundation for the uniqueness of the Beidou system.

In 1985, Chen Fangyun, an academician of the Chinese Academy of Sciences and an advocate of the "863 Plan", proposed the idea of using geosynchronous satellites for positioning and communication, that is, the binary star positioning system, also known as the "active location service" technology system, and later became the original theoretical source of the Beidou plan.

This technology route enables the Beidou system to use only two synchronous fixed point satellites and ground elevation databases in the initial stage to achieve location within the target area. In addition, users can send messages and send location messages and other functions in conjunction with location, so far these are unique functions of the Beidou system.

However, there are also short boards. Through active service to achieve location, the terminal needs to interact with the ground control station through the terminal, while the ground control station solves the problem of intermediate algorithm, which leads to a limited number of users accessing the Beidou one system.

In 2000, China launched its first two geostationary orbit satellites for the first time and put into operation immediately. Since then, China has become the third independent satellite navigation system after the United States and Russia.

The Beidou satellite navigation system has achieved the first step, which is mainly aimed at Chinese users, providing location, time service, wide area differential and short message communication services.

In order to move towards wider space and play a greater role, iteration is coming soon. From 2007 to 2012, the Beidou two system launched 14 satellites, forming the high orbit hybrid constellation structure of China's unique geostationary orbit satellite (GEO) + tilting earth orbit satellite (IGSO) + medium earth orbit satellite (MEO), which laid a solid foundation for further development in terms of precision, anti shielding ability and coverage.

In addition, the technology system of BD1 has been retained, and the technology of "passive location service" has been added to provide corresponding services for the Asia Pacific region. Compared with the "active service", the "passive" technology system has no restrictions on the number of users, and is also consistent with the GPS system in the US.

The positioning of Beidou two is almost the same as that of GPS. But at that time, some technical conditions did not reach the most advanced level in the world, such as atomic clock and global measurement and control point, so Beidou two satellite orbit positioning capability and accuracy will face challenges. In an interview with the economic news reporters in twenty-first Century, Haida chairman Liao Dinghai summed up this.

Since the completion of the 30 satellite launching network in 2020, the Beidou three system has been completed. In addition to the technical line over the years, China adopts the Ka intersatellite link frequency band, which can achieve higher secrecy and communication rate. China has formally launched a perfect global satellite navigation application service.

The Big Dipper, a constellation matrix traditionally used to direct the direction of China, is being introduced into other lights through a sophisticated collaborative way to help defend the country.

Inclusive global four systems

From the perspective of the deployment and evolution speed of satellite navigation system, China is undoubtedly the fastest, and because of the different deployment routes, the uniqueness is obvious.

"The US, European Union and Russia's satellite navigation systems are mainly based on dynamic satellites. The strategy is to enable the least number of satellites to move up and guarantee more than 3 satellites in each place. Our Beidou system uses the combination of geostationary orbit satellite and non geostationary orbit satellite, and its principle is called "rear intersection". Liao Dinghai analyzed that the more dispersed the satellite is, the larger the volume of the space cube formed by the satellite will be, and the more precise the positioning accuracy will be for the users.

Non geostationary satellites are divided into medium orbit satellites and inclined earth synchronous orbit satellites. Liao Dinghai believes that the orbit height of a medium orbit satellite is generally around 20 thousand km, and the distance from the ground will lead to poor positioning accuracy. That is, the geometric distribution factor is better. "Beidou system will be more accurate than GPS." He pointed out.

Therefore, in a comprehensive way, Liao Dinghai said that the performance of Beidou three is no less than that of the US GPS system from the aspects of high-precision positioning, frequency and channel numbers, and the speed of deployment and construction of related systems is also very fast. Of course, during the years when the Beidou system is constantly catching up, GPS system is also constantly updating, adding a lot of new satellite channels.

Guo Jin securities also pointed out in the research report that compared to the previous generation, Beidou three applied more advanced new generation of rubidium atomic clock and the world's leading "inter satellite link" mode, which enabled the Beidou three to increase the positioning accuracy by 2-3 times, reaching the service accuracy of about 4 meters, and the frequency stability increased 10 times than before. Even if the ground stations fail, the Beidou system can provide precise positioning and timing for users through intersatellite links.

The agency believes that the Beidou system has realized the integrated layout of the earth and the sky and built up a precise network space-time system. After the completion of the network, it will be the same as the foreign navigation system, and has a unique advantage.

However, the four largest satellite communication systems in the world are by no means completely opposed or independent competitive relations. The technology of these heavy countries has always been a concurrence relationship. It seems that the four systems of "cutting away from one side" are all embracing.

This is due to the fact that the spectrum resources of the communications world will not be inexhaustible, and that the time taken will be more advantageous. The sharing of spectrum resources between the four systems of the world is different. Sharing is the only way.

"In the past, there were claims that the Beidou system would replace and defeat the GPS system in the future. Liao Dinghai pointed out that in fact, for the civilian experience, the four global satellite navigation and positioning systems will work best together.

For companies in the industry, it is open and compatible with more functions at the chip design level, including RF, baseband, signal processing and algorithm, so that it can receive information from the four major global navigation satellite systems.

"Through these four systems, we can get information from dozens of satellites, and the reliability will be much better. This is also the significance of establishing the GNSS global navigation satellite system. Liao Dinghai continued.

Next challenge

On the one hand, from the perspective of self development, the four systems have "delineated" the next "race" runway.

Cao Chong, chief scientist of China satellite navigation and positioning Association, pointed out, "what else should we do in the next ten years? To put it simply, we need to make good use of the big dipper and upgrade it to realize the leaping development of the new space-time system.

It involves two aspects, one is the deepening of technical iteration, and the other is the application of landing expansion. This has become the trend of industrial chain exploration.

Cao Chong explained that in fact, the weakness of satellite navigation is still obvious: the disturbance of geophysical anomalies such as sunspots and geomagnetism in the solar terrestrial space, physical occlusion, shielding and multipath and reflection, as well as intentionally or unintentionally interfering threats and disturbing spoofing attacks, will result in abnormal interruption and failure of GNSS signal reception.

To this end, our country has been promoting a large-scale foundation reinforcement system landing, and on this basis, the accelerated deployment of star based augmentation system is also in the schedule.

In short, these two kinds of technologies are starting from signal enhancement of ground reference stations and signal enhancement between satellites, and the four major systems in the world are actually firmly implementing.

Liao Dinghai told the twenty-first Century economic news reporter, "in addition to the regional augmentation system, the development of integrated navigation technology will become another important direction of satellite navigation technology."

Specifically, on the one hand, satellite navigation technology will continue to develop itself, by upgrading core components, thereby reducing power consumption and reducing costs. Haida has launched the baseband chip research and development based on the launch of RF chip.

On the other hand, satellite navigation and inertial navigation technology can be combined more deeply. Because the satellite navigation system must receive signals from the sky, it can not be located at the location where the signal is interrupted, and the inertial navigation technology can be independently positioned without external influence. However, as time goes on, the errors of inertial navigation and positioning will gradually increase, which requires the real-time positioning of satellite navigation to eliminate the error accumulation. Therefore, the effective integration of the two can solve the key problems in practical application.

Technology and application have always complemented each other. The wave of "new infrastructure" is clearly opening up huge imagination for "Beidou +" and "+ Beidou".

Liao Dinghai thinks that 5G has opened the new industrial ecosystem for the Beidou system. With the gradual loading of the Beidou precise location service, the prospect will be very broad.

The latest Beidou satellite navigation system is brilliant. It is the first time to use the Beidou System in the state's third summit survey of Mount Qomolangma, which is of great significance to the industry.

Based on the unique ability of Beidou three, especially in the process of sudden disasters, its importance is particularly prominent. According to Li Changjiang, during the Wenchuan earthquake in 2008, when the network and communications were completely broken, all the forces could accurately locate through the Beidou user machine, and the first time to feedback the disaster field information to help the public out of danger.

There are also rapidly developing autopilot, robotics, Internet of things, and so on. Huge application scenarios are calling the "National Heavy device" to us.

As Cao Chong described, the application of satellite navigation is so extensive and even infinite that its service is restricted only by people's imagination, and only unexpected, can not be done.

In the near future, when we mention satellite navigation systems and mention the "Big Dipper", we will no longer think about mobile phones, but our antennae will extend to infinity.