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CCTV News (Focus Interview): At 14:07 on June 25, the Chang'e-6 returner carried lunar samples from the back of the moon and landed safely in the predetermined area of the Siziwang Banner in Inner Mongolia. Xi Jinping, General Secretary of the CPC Central Committee, President of the People's Republic of China, and Chairman of the Central Military Commission, sent a congratulatory message, on behalf of the CPC Central Committee, the State Council, and the Central Military Commission, to extend warm congratulations and sincere greetings to the Chang'e-6 mission headquarters of the lunar exploration project and all comrades participating in the mission. In his congratulatory message, Xi Jinping pointed out that Chang'e-6 achieved the return of samples from the far side of the moon for the first time in human history, which is another landmark achievement of the mainland in building a space power and a science and technology power. Over the past 20 years, all the comrades involved in the development and construction of the lunar exploration project have carried forward the spirit of lunar exploration, bravely scaled the peak of science and technology, made major achievements that have attracted worldwide attention, and embarked on a high-quality and high-efficiency road of lunar exploration. Next, let's take a look at the challenges that Chang'e-6 has experienced in this lunar exploration trip.
On June 25, 2024, the Siziwangqi Space Landing Site in Inner Mongolia welcomed a special "guest", and after 53 days of space odyssey, the Chang'e-6 returner successfully landed. Chang'e-6 brought back a generous gift to Earth - a lunar sample from the back of the moon, which is also the first time that humans have achieved sampling and return from the back of the moon.
This morning (June 26), the Chang'e-6 returner has been airlifted to Beijing, and follow-up sample storage, analysis and research will also be carried out. From its launch on May 3 to its return on June 25, the Chang'e-6 probe successfully completed its mission, once again leaving China's lunar footprints on the moon. And in these 53 days, behind the moon, which is invisible to the naked eye, Chang'e-6 has experienced one challenge after another. Among these challenges, the most notable is the landing on the moon.
At about 6 o'clock on June 2, the Chang'e-6 probe is about to land on the far side of the moon. The mission's pre-selected landing area, the South Pole on the far side of the moon and the Aitken Basin, has a drop of more than 10 kilometers, which is like landing a small truck into a lofty mountain, which requires not only precise obstacle avoidance, but also advanced guidance, navigation and control systems to ensure a safe landing.
At 6:09, the Chang'e-6 lander and ascender assembly began to implement power descent, and then the main engine was turned on. In the meantime, the combination performs rapid attitude adjustment and automatic obstacle detection, and selects the approximate safety point according to the light and darkness of the lunar surface. Chang'e-6 hovers at an altitude of 100 meters from the landing site, and the three seconds of hovering are particularly critical for landing on the moon.
Guan Yifeng of China Aerospace Science and Technology Corporation: "Imaging and obstacle identification when hovering, and then avoiding it, is equivalent to two parts, first eye confirmation, a glance at what is relatively flat, remember that place, and then transmit that place to the brain, know that it is flat and then move over, and then descend above the flat area." ”
When experts say eye, they mean a three-dimensional imaging sensor. Before landing on the moon, the 3D imaging sensor uses laser 3D scanning to take precise pictures to detect obstacles on the lunar surface, and finally select a landing site to complete the landing. At a test site at Tongji University, large and small planks are used to verify the accuracy of laser imaging technology by simulating the undulations of the ground seen from the air at different heights and angles.
Xie Huan, Dean of the School of Surveying, Mapping and Geoinformatics of Tongji University: "For landing and obstacle avoidance, the main concern is whether the ground is flat. To avoid craters and rocks larger than 20 centimeters, we simulated different scenarios in the site, large and small craters and rocks of different sizes, to replicate as much as possible the scenes on the surface of the moon that may threaten a safe landing. ”
However, no matter how accurate the stationary experiment on the ground is, it cannot cope with the shaking of the detector during actual operation. It's like taking a picture on a bumpy car, and the imaging is very poor. The response that the research team came up with was one word: fast. The sensor can perform a detailed survey of a certain range of the moon's topography in 0.25 seconds. And in just 3 seconds of hovering, the autonomous obstacle avoidance system has only three chances to make a judgment to complete all the measurement and calculation work.
Chang'e-6's autonomous obstacle avoidance capability helped it stay away from dangerous areas and successfully land on the far side of the moon. The successful landing is only the first critical step in completing the lunar surface mission, and the next sampling mission is even more daunting. Limited by the long relay communication time on the far side of the moon, Chang'e-6 uses fast intelligent sampling technology to shorten the effective working time of lunar surface sampling to less than 20 hours, and collects lunar samples through drilling tools and robotic arm surface sampling.
Shi Wei of China Aerospace Science and Technology Corporation: "After the moon falls, the camera must first image the entire sampling area. The approximate fluctuation of the sampling area, whether there are stones or not, to avoid the risk area, so we must first restore the environment of the entire lunar surface in the infield. ”
At the "pre-training ground" known as Chang'e-6, researchers quickly restored the landform around the landing site according to the image of the landing area taken by Chang'e-6 and transmitted back to the ground laboratory of the Fifth Academy of China Aerospace Science and Technology Corporation. After landing on the moon, Chang'e-6 did not start sampling directly, but first carried out experimental verification here and uploaded the operation instructions to the moon before starting actual sampling.
The drilling process lasted about 3 hours, and lunar samples of different depths were obtained from the far side of the moon. In addition to borehole sampling, lunar samples were also collected by surface shoveling of the robotic arm to achieve automatic sampling at multiple points. To this end, the researchers designed more than 10 surface sampling collection points. Compared with Chang'e-5, Chang'e-6 has been greatly improved in terms of intelligence and autonomy.
Ma Ruqi of China Aerospace Science and Technology Corporation: "As long as one command is issued, it will connect the entire task, such as touching the moon, sampling, and then lofting, and only one instruction is needed to connect it all in the whole process, which improves efficiency." ”
To the surprise of the astronauts, after the surface sampling was completed, the word "medium" appeared on the lunar surface.
Jia Xiaoyu of China Aerospace Science and Technology Corporation: "At the beginning, the sampling point was selected only according to the graphics seen on the surface, and we will dynamically adjust the position of the sampling point according to the sample turned out. Originally, we might have shoveled a few more shovels in addition to the word '中', but in the end we found that after the last stroke of the word '中' was formed, the sample container was almost full. All kinds of accidents have led to the creation of the word 'China', which may be destined for China to leave its mark on the moon. ”
The Chinese imprint left on the back of the moon may be just a beautiful coincidence, but this imprint not only records the work trajectory of the Chang'e-6 probe, but also witnesses the firm determination and unremitting efforts of the Chinese for lunar exploration. After the sampling work was completed, the five-star red flag carried by the Chang'e-6 lander was successfully deployed on the far side of the moon.
Throughout the history of the world's aerospace industry, before Chang'e-6, all human lunar samples were located on the front side of the moon. Therefore, scientists all over the world are paying attention to the lunar back samples brought back by Chang'e-6 for the first time.
Chang'e-6 carried four international payloads from ESA, France, Italy and Pakistan, among which the laser corner reflector developed by the Italian National Institute of Nuclear Physics for ranging and positioning is an instrument capable of ranging and positioning with millimeter accuracy. In the laboratory, one of the main tasks of the researchers is to simulate the space environment through the vacuum chamber, constantly testing the accuracy of the laser corner reflector. The official said that China's openness and cooperation in the field of space exploration is impressive.
At the Institute of Geology and Geophysics of the Chinese Academy of Sciences, laboratories are already ready for the return of Chang'e-6. In 2021, the research team revealed that magmatic activity still existed on the moon 2 billion years ago through the study of Chang'e-5 lunar samples, refreshing mankind's understanding of the moon's magmatic activity and evolutionary history. Scientists hope that the study of Chang'e-6 samples will lead to more new discoveries.
Li Xianhua, academician of the Chinese Academy of Sciences and researcher of the Institute of Geology and Geophysics of the Chinese Academy of Sciences: "The Antarctica-Aitken Basin is the oldest impact crater on the Moon, the largest impact crater, and even the largest impact crater in the entire inner solar system. This impact is of great significance for the evolutionary history of the late Moon, and we naturally ask when it hit? This time we went to this place to take samples, and it is very likely that we have taken some records related to this impact, and we have measured its age. Second, the front and back sides of the moon are different, and how they are different requires samples to analyze. ”
The first step after the research team obtained the lunar soil was sample preparation, and the selection work should be carried out under the microscope, and any extra shaking of the hand would cause the particles to be unable to be effectively selected, and follow-up research would be impossible.
Experts said that the precious lunar samples collected by Chang'e-6 will provide more valuable data and information about the moon for mankind, and are expected to deepen the study of the origin and evolution history of the moon.
Wu Fuyuan, academician of the Chinese Academy of Sciences and researcher at the Institute of Geology and Geophysics of the Chinese Academy of Sciences: "We used to think that the moon died 3 billion years ago, but the samples of Chang'e-5 found that there was magmatic activity 2 billion years ago, and whether there was any later, we are not sure that there must be no more, so human understanding of the moon is very limited." It has been 20 years since the Chang'e project, and it has only been a few years since we returned a few samples, so we must turn our aerospace superiority into a scientific superiority and concentrate our efforts on scientific output and breakthroughs. ”
From the launch on May 3, the journey of 380,000 kilometers to the moon to the accurate implementation of near-moon braking. From the successful landing on the far side of the moon, intelligent sampling on the lunar surface, to the ascent from the lunar surface, on-orbit rendezvous and docking, sample transfer, to today's return to the earth's homeland and the successful completion of the mission, Chang'e-6's lunar exploration journey has lasted 53 days, and every step has included the efforts of countless scientific researchers. After completing the necessary ground processing work, the recovered Chang'e-6 returner will be airlifted to Beijing to open the cabin and remove the sample container and carry. The China National Space Administration will hold a handover ceremony at the right time to officially hand over lunar samples to the ground application system, and then carry out sample storage, analysis and research. We look forward to the good news from scientists and believe that the work of Chang'e-6 will help us unravel more mysteries about the Moon and the solar system.