Li Deren, winner of the highest national science and technology award: above the sky, polish the "Oriental Eye"

Text | "China Science News" reporter Li Sihui

From relying on 85% of satellite data imported from abroad, to achieving 85% self-sufficiency, and then to exporting to other countries, he led the team to make the mainland surveying and mapping remote sensing technology step by step from backward to the forefront of the world, and established a real "Chinese's own global observation system".

He is an academician of the Chinese Academy of Sciences and the Chinese Academy of Sciences and a professor at Wuhan University. On June 24, Li Deren, as the winner of the 2023 National Highest Science and Technology Award, wore a heavy medal at the Great Hall of the People in Beijing.

Courtesy of Wuhan University

"5, 4, 3, 2, 1, ignition!" As the red orange flames burst out in an instant, the Kuaizhou-11 carrier rocket roared all the way into the sky.

At 12:15 on May 21, the "Luojia-3" scientific experiment satellite 02, independently developed by the team of Wuhan University, carried the Kuaizhou-11 carrier rocket, was successfully launched at the Jiuquan Satellite Launch Center and successfully entered the scheduled orbit.

Li Deren, academician of the Chinese Academy of Sciences and academician of the Chinese Academy of Engineering, was very happy to receive the news from Jiuquan. Gong Jianya, an academician of the Chinese Academy of Sciences who served as the satellite's chief scientist, was a student of Li Deren and a member of the surveying, mapping and remote sensing team. Li Deren told China Science Daily that the satellite has 0.5-meter resolution panchromatic imaging and 10-meter resolution hyperspectral imaging, and the data will be more efficient and accurate, and the acquisition will be more convenient.

From backwardness to the forefront

In 1985, Dr. Li Deren returned from Germany and joined the Wuhan Institute of Surveying and Mapping (merged into Wuhan University in 2000) to teach, and was promoted to professor the following year. In 1991 and 1994, he was elected as a member of the Chinese Academy of Sciences and an academician of the Chinese Academy of Engineering.

He told China Science News: "Although the time from my doctoral graduation to being rated as a professor and elected as an academician was relatively short, at that time I had carried out decades of research and practice, laid a very solid foundation, and just caught up with the opportunity of the party's talent policy." ”

After returning to China, he received an important and arduous task of mapping the border between China and a neighboring country in an area with landmines.

The long border line is either hidden in the mountains or in dangerous places, and there may be mines underground. How to quickly find out the situation in a short period of time? Manual mapping alone is certainly not enough. Li Deren proposed to "put GPS on the plane". Using "GPS aerial triangulation" technology, he quickly completed the boundary mapping task without the need for ground control points. This is the first time that the Chinese have mapped the boundary through the on-board GPS system. Since then, he has relied on this technology to complete aerial surveys and maps of Hainan Island, Tiger Leaping Gorge and other places on the mainland.

Faced with the current situation in which the mainland's satellites, aviation, and ground systems lagged behind others, Li Deren was anxious. In 2002, Li Deren, as the leader, put forward a proposal to the state on "building a continental high-resolution earth observation system" (hereinafter referred to as the high-resolution special project). In 2010, the high-score special project was officially launched, and the expert group leader was Wang Liheng, academician of the Chinese Academy of Engineering and China Aerospace Science and Technology Corporation, and Li Deren served as the deputy leader.

More than 10 years have passed, and the high-resolution special project has basically met the major needs of the mainland's economic development, national defense construction, and people's livelihood, and enabled the mainland's satellite remote sensing and application to reach the world's advanced level. "This achievement was created with the wisdom of the Chinese and our mathematical and process control methods in the context of limited components." Li Deren said proudly.

Driven by the driving force of independence and self-reliance, Li Deren also led the team to develop a continental space-air-ground 3S integrated surveying, mapping and remote sensing system, and built an independent and controllable domestic geographic information technology system.

From relying on 85% of satellite data imported from abroad, to achieving a self-sufficiency rate of 85%, and then to exporting to other countries, mainland surveying, mapping and remote sensing technology has gradually moved from backwardness to the forefront of the world, establishing a real "Chinese own global observation system".

Serving the country and the people

There is one thing that Li Deren still can't let go.

In 2008, a major earthquake struck Wenchuan. In the process of earthquake relief, the lack of remote sensing satellites has made it impossible for people to obtain post-disaster information in the first time, and they cannot provide more help to rescuers within the 72-hour golden rescue time. This has become an intractable pain in Li Deren's heart.

He said that at that time, the mainland only had remote sensing satellites with a resolution of 3 meters, and the number was very small, so he could not "see" the situation in Wenchuan, so he could only ask friends all over the world for satellite data. On the third day, Italian scientists sent the relevant data.

During the three days of anxious waiting, Li Deren felt deeply guilty. "We have been doing remote sensing all our lives, but we can't meet the requirements of earthquake relief, we are ashamed!" "If only there were remote sensing satellites with a resolution of 0.5 meters at that time, we could conduct accurate scanning over Wenchuan, find the collapsed houses as soon as possible, and cooperate with officers and soldiers to rescue more people." Fortunately, after more than 10 years of hard work, the mainland remote sensing satellite has reached this accuracy.

In fact, remote sensing technology still played a significant role in the Wenchuan disaster relief at that time. For example, Tangjiashan Mountain was cut in half in the earthquake, forming a hanging lake with a water storage of nearly 300 million cubic meters, and if it collapsed, it would bring great disaster to millions of people in Mianyang and other places. It is difficult for the relevant departments to decide what to do.

At the critical juncture, Li Deren took the initiative to rush to Wenchuan and led the team of the State Key Laboratory of Surveying, Mapping and Remote Sensing Information Engineering of Wuhan University to scan the topography of the dammed lake in Tangjiashan, and used aerial remote sensing to obtain detailed data such as water level, water flow velocity, and pressure of the dammed lake, and completed the most detailed three-dimensional digital elevation model.

According to the results of the data analysis, they believe that although the dammed lake in Tangjiashan is dangerous, it is still stable, and the risk can be eliminated by the method of open channel diversion. The team reported the data to the Earthquake Relief Headquarters, providing a scientific basis for the correct handling of the danger.

It is also disaster relief, and on the occasion of flood control in the summer of 2023, Li Deren's team put forward a shocking suggestion - "Quickly organize an evacuation". It was this suggestion that turned the tide for more than 6,400 people.

At that time, the "Luojia-2" satellite, independently developed by Li Deren's team, obtained radar images over the affected areas in Hebei Province and observed a breach in an embankment. "At first, the breach was not big and not easy to detect, but through the analysis of satellite remote sensing data, combined with the analysis of water flow velocity and pressure, we judged that the breach would soon cause a catastrophe." The team immediately issued an alert to the relevant authorities. This timely warning proved to have avoided a "catastrophe that would have been difficult to prevent" by traditional means. "All-day, all-weather, engineering-level application" is one of the advantages of radar remote sensing.

From supporting the Qinghai-Tibet Railway to participating in the Wenchuan earthquake relief, from the security of the Beijing Olympic Games to the digital Dunhuang project, from assisting the agriculture and forestry departments to find out relevant data to providing technical support for epidemic prevention and control, from the feasibility analysis of the South-to-North Water Diversion Project to the data collection of urban congestion...... In Li Deren's view, the needs of the country and the people are the greatest driving force for scientific research.

As a leading scientist in photogrammetry, remote sensing, and geospatial information science, Li Deren has been highly recognized by the international scientific community. In June 2022, he was awarded the Block Gold Award, one of the most influential awards in the field of international photogrammetry and remote sensing, and was the first person in mainland China to receive this honor.

Find another way to make a breakthrough

At present, there are four major satellite positioning systems in the world: the Global Positioning System (GPS) of the United States, the GLONASS Satellite Navigation System (GLONASS) of Russia, the Galileo Satellite Navigation System (Galileo) of the European Union, and the Beidou Satellite Navigation System (BDS) of China. Under normal circumstances, the construction of a satellite positioning system requires the layout of a reference station on the ground to improve the accuracy of the satellite navigation system to the centimeter or even millimeter level.

At that time, a certain country deployed a satellite navigation system and built thousands of base stations in many countries and regions, including China. In 2020, China deployed Beidou, but the country refused to allow China to build a base station there and blockade the mainland.

In this case, Li Deren organized a team to tackle key problems and creatively researched China's first low-orbit satellite navigation augmentation system and indoor and outdoor integrated sub-meter mobile phone navigation and positioning system. With these systems, China's Beidou satellite has reached the same level of GPS positioning accuracy as a state-built base station, and a number of technical performance surpasses GPS.

This is undoubtedly a major and disruptive innovation. The achievement of this major innovation means that China has led the world in this high-tech technology. At present, some developed countries, including the United States, are struggling to follow up with this technology.

"Sit on the ground and travel 80,000 miles a day, survey the sky and see a thousand rivers from afar." In view of the problems of "high cost, low efficiency, instability, and few applications" in mainland satellite remote sensing, Li Deren led the team to put forward an extremely ambitious plan - the "Oriental Eye" constellation plan for the networking of more than 200 satellites.

In order to polish the "Oriental Eye" more brightly, Li Deren worked the accuracy and quality of the satellite. Satellite remote sensing resolution from 5 meters, 3 meters, 2 meters, 1 meter to 0.5 meters, this series of data intuitively records the whole process of China's satellites from scratch and from existence to good.

The team expects to launch 252 satellites by 2030, including high-resolution optical and radar satellites, hyperspectral satellites and thermal infrared satellites, forming a "satellite network". These satellites will help people see every place on Earth quickly, clearly, accurately, completely, and understandably.

"At that point, the cost of using our satellites will be lower, and everyone will be able to use satellite data easily, from 'playing WeChat' to 'playing satellite'. These satellites will create trillions of new quality productivity for the country and serve the sustainable development of human society. When it comes to the future, Li Deren is full of hope.