Thrilling 690 seconds: Experts explain the fourth landing on the back of the moon


The first photo of the moon on the back is coming!

Xinhua News Agency, Beijing, January 3 (Reporter Yu Fei, Hu Wei, Quan Xiaoshu) 嫦娥 4th on the 3rd landed in the Moon's Antarctic – Aitken Basin Feng Yukamen crater, became the first human to land softly on the back of the moon detector. The entire landing process can be described as thrilling, and the lunar exploration experts detailed the process.

Wu Weiren, the chief designer of the Chinese lunar exploration project, is in Sichuan. He said in a metaphor: The No. 3 landed in the Great Plains of North China, and the No. 4 landed in the mountains of southwest China.

He said that the landing area of ​​the No. 4 landing area is equivalent to one-eighth of the landing area of ​​the No. 3, and there is a mountain 10 kilometers above sea level. The elevation of the Fengqi Kamen crater in the Aitken Basin is minus 6 kilometers. Unlike the smooth parabolic trajectory of the 嫦娥3, the 嫦娥4 is close to vertical landing.

“Short landing time, difficulty, and high risk are a big test for us.” Wu Weiren said.

He said that during the process of the moon, most of the No. 4 inherited the soft landing technique of the No. 3 lunar surface. The whole process was about 700 seconds, all relying on the detector to complete itself, and the ground could see the landing process through the relay star. But no intervention is implemented.

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On January 3, at the Beijing Aerospace Flight Control Center, researchers celebrated the success of the landing. Xinhua News Agency reporter Jin Liwang photo

Sun Zezhou, chief designer of the No. 4 Detector of the Fifth Academy of Aerospace Science and Technology Group, said: “Our information on the lunar topography mainly comes from the remote sensing data of the previous month, including the remote sensing data of Chang'e-1, Chang'e II and some foreign satellites. But these Data can't provide us with accurate terrain information. We can't know where there are big stones, more of the overall macro information and statistical probability. Finally, landing depends on the detector to identify obstacles and obstacles.”

Zhang Wei, director of the No. 4 Detector Project of the Fifth Institute, said that the No. 4 system has considered how to improve the accuracy of the landing. The track correction was added at the end of the month, and the power reduction control strategy was adjusted. The detector should reach above the landing zone when it is relatively high from the moon, and then descend vertically, so that the complex and rugged terrain on the track will not affect the landing.

Li Fei, the chief designer of the No. 4 Landing Device of the Fifth Institute, introduced that the moon will first decelerate the detector by changing the thrust engine, reducing the speed of the detector from the 1.7 km per hour to nearly zero, just like the car brake. Then adjust the attitude of the detector and drop vertically.

Wu Xueying, deputy chief designer of the No. 4 detector of the Fifth Hospital, said that when the detector is about two kilometers from the moon, a rough obstacle avoidance is first implemented. Through optical imaging, the projection of the terrain caused by sunlight is used to identify obstacles. Large craters and large rocks can be identified.

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The image taken by the camera after the soft landing on the back of the Moon 4 detector (photo taken on January 3). Xinhua News Agency (for the National Space Agency)

After that, the No. 4 hovered at a distance of 100 meters from the lunar surface, using laser scanning to achieve a fine obstacle avoidance. At this time, it can identify smaller obstacles, and at the same time can recognize the slope of the ground, and find a safer by calculation. The location serves as the landing site.

Then the detector drops again. Finally, the engine stops working 2 meters away from the moon. The detector falls in a free fall. The four legs on the lander buffer the impact energy of the landing, allowing the lander to land stably on the moon. .


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