(original title: the first man! Chang'e four why can do this thing on the moon?)
1 11 April afternoon came Herald, lunar exploration, Chang fourth task successfully, for the first time in human history the spacecraft lunar soft landing and lunar exploration, monitoring and communication for the first time on the back of the moon and the earth, unveiled a month old back, leaving the first human lunar exploration lines of footprints in the back of the moon, and opened a new chapter in the human exploration of the mysteries of the universe. This is the China Aerospace Science and technology personnel, in spite of high risk and high difficulty, overcome difficulties, innovative results.
This afternoon, the lander and Rover Yutu II successfully beat each other remarkable Chang fourth detector, and sent back photos, marking the Chang fourth task successfully. In the past week, Chang fourth became the focus of the whole world.
On the back of about 400000 kilometers from the earth's moon, known as the "fam fam", in 2019 before millions of years on the back of the moon first welcomed visitors to earth. Beijing time on January 3rd at 10:26 in the morning, Chinese developed Chang four spacecraft successfully landed on the moon on the back of the von Carmen crater in the intended landing area.
11:40, Chang'e four returns the world's first shot close month back image, the first human close to uncover the mystery of ancient month back.
A smooth landing after more than 11 hours, the goddess of the moon and moon landing No. four No. two Rover successfully isolated rabbit No. two Rover -- lunar rover successfully arrived on back surface. Rabbit No. two is a man on the moon of the seventh lunar rover, is also the first car in the back of the moon of the lunar rover.
Chang'e four landed on the moon on the back of the news release, attracted the attention of the international mainstream media and international aerospace experts. AP, Reuters, AFP and other international mainstream news agency also have to "human first" to describe the Chang fourth successful landing on the moon on the back of the news. The British "Guardian" is defined as "a huge leap in human space exploration of the landing". NASA Administrator Braeden J Tin for the first time published tweets on China Chang'e four landed on the back of the moon, and pointed out that this is the first human, is an impressive achievement "".
Professor at the University of Houston, building space center manager Orika Banova said: "Chinese Chang'e four landed on the moon on the back of the news, absolutely is one of the important achievements of the history of human space, this action will be able to lift the veil on the back of the moon, so this is a very important achievement."
On the back of the moon for humans, there are many unknown waiting for the answer. Because the earth earth strong gravitational tidal locking, let the moon always face toward the earth, so the humans on earth can only see the moon in front, the back is invisible. In order to human detector safe landing on the back of the moon, the biggest challenge is the lunar terrain.The moon on the back of the distribution of a large number of craters, craters, mountains of ups and downs, rugged, flat landing area selection of the ideal is very small. Chang'e four development team according to the requirements of the project, through the research for many months on the back of the terrain analysis, the final choice on the back of the moon in the Antarctic basin Aitken von Carmen crater as scheduled landing site.
Aerospace Science and Technology Group Five Chang'e four lander director general designer Li Fei said: "the No. three in lunar surface, the topography is relatively flat, then choose a 360 km long, 90 km wide area of flat area. To Chang fourth, the final choice in the southeast side of von Carmen crater, choose a relatively flat area in the middle of the pit edge and central peak, selected by a 30 km in the area of 50 square kilometers, far less than the chang'e-3 front landing area."
Von Carmen crater is one of the most ancient crater on the far side of the moon after weathering for billions of years, on the back of the terrain of the moon, is a relatively flat area. Here the latitude and Chang'e three landed area latitude relatively close, because the "Chang'e four" is "the No. three" backup device parameters are basically the same, choose the same latitude for Chang'e four to make a soft landing. At the same time, scientists speculate that the von Carmen crater with a long history, may be retained in the formation of the moon and the origin of the solar system with traces of the scientific exploration of great value.
Chief architect of the lunar exploration program, China Academy of engineering, Wu Weiren said: "the crater is very deep, and large diameter is 180 km, scientists believe that the impact crater, the mantle, inside the shell of things to hit out, this is the most valuable, so decided to go inside the pit detection we need to find the maximum value, the scientific exploration of the."
Chang'e four landing area to Chang'e three landed area 5%, Chang'e four to accurately fly to this small landing area, the biggest difficulty is to improve the accuracy of landing, the key step to control the landing precision, is selected in the initial orbit around the moon began to decline.
Aerospace Science and Technology Group Five Chang'e four lander deputy director general designer Zhou Wenyan said: "the initial decline and Chang'e three, Chang'e three point range is bigger, it allows changes in the range of 10. The Chang'e four landing point precision range is relatively high, for this point is allowed to have only a few tenths of deviation. In order to get the initial points we calculate the tens of thousands of tracks, and choose a suitable track engineering constraint energy from the province, and on it in flight to continuously adjust, make it precisely at this initial point."
The initial point of the distance from the moon back down at an altitude of 15 kilometers from the power down command is issued to the landing, only a short 720 seconds, a number of links to the No. four experience of main reducer, quick adjustment, close, hover, obstacle avoidance, due to high speed flight distance is short, the change of the ground speed cannot follow the instructions to upload Chang'e four speed and position, so this stage of Chang'e four is completely independent of control, avoid obstacles, autonomous landing site selection of ideal. In this stage, the biggest risk of Chang'e four may have hit a peak or falling into the pit. In order to deal with this challenge, Chang'e four development team designed a new autonomous navigation control landing strategy.
Aerospace Science and Technology Group held the No. four guidance navigation and control system of chief designer Guan Yifeng said: "the No. three the landing is a relatively steep descent process, due to the dark side of the moon Chang'e four peaks, in order to protect the lander down process does not hit the moon mountain, so similar to the designated parachute landing. The engine in the 15 km boot deceleration, deceleration process automatically to the von Carmen crater above the level, its speed is basically eliminated, probably after 6 kilometers, the entire vertical down landing detector."
Aerospace Science and Technology Group held the No. four detector system project executive director Zhang He said: "the first one is that, no surveillance inspections like machine C shot, you can see the front not far from there is a pit, the pit about 20 meters from the landing point, that obstacle avoidance has played a good effect. Because if a landing leg stepped to the edge of the pit, may turn over, still feel very proud, we finally found a good landing point."
The No. four to the successful completion of the lunar soft landing and lunar exploration, is also facing one of the biggest obstacles, that is the communication problem. Due to the moon and back to direct communication, must be used to relay satellite relay mode. Therefore, our country launched the world's first lunar satellite relay communication "bridge", undertake the Chang'e four lunar and earth communication task.
Aerospace Science and Technology Group held the No. four relay star general designer Zhang Lihua said: "in the lunar orbit or beyond Earth orbit in addition, Queqiao should be said to be the first dedicated relay communication satellite, it is on the back of the lunar lander and Rover, the distance is far, the farthest reaches nearly 80 thousand kilometers, how to ensure the relay communication performance in such far communication distance, it should be said that we are facing a challenge."
Compared due to the ability to relay satellite receiving signal with large aperture antenna equipment to the ground control station, and the far distance, the received signal is very weak, not to the mobile phone signal 1/10000, the data transmission rate of number is very low. In the process of development, scientific research personnel once faced with problems of poor quality of signal demodulation.
Aerospace Science and Technology Group held the No. four relay load technology manager Zhang Aibing said: "we used the new algorithm to solve this problem, the test should be thousands of times the test."
The moon carrying four spacecraft Rover lunar rover called Yutu No. two, and Chang'e three carrying moon rover compared with a lot of improvement.Moon rover in the fall months to second months after the day when a sudden failure, a total of only traveling more than 110 meters.
Chief architect of the lunar exploration program, China Academy of engineering, Wu Weiren said: "I started in the field of systems, personnel, scientific and technical personnel to do everything possible to rescue, but in the end did not come to the rescue, sorry. The whole project was very successful, but left a flaw, it also reflects our understanding of the lunar environment is not thorough. There are some main cable exposed after high temperature low temperature after surface catalytic cable in the process of moving rub short-circuit."
Aiming at the fault rabbit appeared, the rabbit No. two were targeted improvements. Not only the cable tie is more sophisticated, but also take the design of fault isolation.
Aerospace Science and Technology Group held the No. four detector system designer Sun Zezhou said: "the problem of a point, we need to make effective isolation system. Effective isolation is not to the further expansion of the fault, which affects only control in small area. This system can afford to an area within a range, the equivalent of our electricity at home, not because of a short circuit, causing the system can not be used."
Back due to complex terrain, researchers are most worried about the rabbit No. two lost contact with the ground. To this end, the researchers independently of rabbit No. two has been upgraded, including independent dormancy, independently deal with the light shielding. Low temperature or lost to the state to "sleep", and then work out the sun.
At present, Chang'e four lander and Rover rabbit No. two equipped with scientific instruments are starting to work, including the low-frequency radio spectrometer scientists particularly promising. Because here all the year round back on earth, can shield the interference of radio signals from earth, the universe may provide for the low-frequency radiation study of the sun, planets and solar system objects use.
Aerospace Science and Technology Group held the No. four detector system project executive director Zhang He said: "a detection method of the space frequency radio observations and astronomers have always dreamed of, international Americans sent two satellites, of course not only do low frequency radio observations, but the other sun do observations, funds should be in about 2000000000 yuan. On. We have four back to the moon, the first is better than the low-frequency radio environment test on the track, but also the realization of load in funds is very limited, it should be said is a big innovation."
It is understood that in addition to the development of our own scientific loads, Chang'e four Mission in cooperation with Russia, Holland, Saudi Arabia, Germany and Sweden and other countries, with multiple international load, which is also the first time in China's lunar exploration project. It is especially for NASA, the operation of the United States is the lunar orbit LRO satellite, to observe the Chang'e four landing activities, the Chinese side for cooperation.
The chief designer of lunar exploration project Chinese Academy of Engineering academician Wu Weiren said: "we are working together with the United States, to provide accurate data we track, and accurate landing time and accurate landing site. We also hope that they can carry out more effective cooperation in this regard, we welcome them to observe the Chang fourth lander and rover. I think the lunar exploration project is the cause of peace, is humanity's common cause, we should have this cooperation mind and great gesture."
The No. four in the back of the moon smooth soft landing, marking the Chinese have full ability to reach the moon. The project after a successful mission, Chang'e four will be transferred to the task of scientific exploration stage, the lander and rover will continue to carry out the position detection and lunar exploration. Chinese lunar exploration project, "around, down, back to three, we have successfully out of the first two steps, the next step, Chang'e five will perform the" back "of the task. We expect the Chang'e five smoothly Chinese first lunar automatic sample return mission.
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