Interesting facts about the history of the Chinese lunar program and the Chang'e-4 space mission

Much is hidden behind the fences of the polygons and the walls of the laboratories of the Chinese Academy of Space Technology during the implementation of lunar research space programs, but some of the information is still kindly made available to the public.

In continuation of this publication.





Brief Chinese history of the Moon:

1991: Chinese space industry experts offered to launch their own (including independent from other countries) moon exploration program.

1998: Chinese scientists begin planning the lunar program, discuss the details of research and confirm the feasibility of the space mission on their own, overcome the first scientific and technical problems that have arisen at the initial stage.

January 2004: The Chinese lunar exploration program, named “Chang'e” (in honor of the Chinese goddess of the moon), was officially launched. The first automatic satellite, which is planned to be put into orbit of the Moon, was named “Chang'e-1”. The country's ambitious lunar project includes three phases: unmanned exploration of the moon, sending people to the moon, and creating a base on the moon.

October 24, 2007: The Changzheng-3A launch vehicle with the Chang'e-1 satellite was successfully launched from the Xichang Chinese Cosmodrome.

November 7, 2007: the Chang'e-1 satellite successfully entered the 127th minute lunar orbit at an altitude of 200 km.

October 2008: the start of the second phase of the Chang'e-2 program was officially approved by the State Council of the People's Republic of China.

November 12, 2008: China releases its first complete map of the Moon's surface, created on the basis of data obtained from Chang'e-1.

March 1, 2009: The pioneer of the Chinese lunar mission, the satellite Chang'e-1, which made its orbital flight for 16 months, completed its work with a controlled fall on the lunar surface.

October 1, 2010: The Changzheng-3S carrier rocket with the Chang'e-2 satellite was successfully launched from the Xichang Chinese cosmodrome, then the Chang'e-2 satellite entered the 118-minute Lunar orbit at an altitude of 100 km.

July 9, 2011: the Chang'e-2 satellite left the lunar orbit to Lagrange point L2 of the Sun-Earth system (1.5 million kilometers from the Earth) to conduct scientific experiments.

August 25, 2011: After a 77-day voyage, the Chang'e-2 satellite went into orbit around the L2 point.

February 6, 2012: China released an updated, more detailed lunar map based on data from the Chang'e-2 satellite.

July 14, 2013: the satellite "Chang'e-2", becoming an artificial asteroid of the solar system, was distant by 50 million kilometers from Earth.

December 3, 2013: The Changzheng-3V launch vehicle with the Chang'e-3 station was successfully launched from the Xichang Chinese cosmodrome.

December 14, 2013: the Chang'e-3 descent vehicle lands in the crater of the Rainbow Bay on the visible side of the moon. As part of the landing device "Chang'e-3" is the first Chinese lunar rover "Yuytu".

January 25, 2014: the “Yutu” rover was technically immobilized (elements crashed as a result of a collision) after overcoming 114.8 meters on a complex lunar surface.

October 23, 2014: The Chang'e-5T1 automatic lunar station was launched with the help of the Changzheng-3C launch vehicle from the Sichan space center. The purpose of the project is to test the return to Earth of the descent vehicle for the further use of this technology in the Chang'e-5 mission.

October 31, 2014: the descent vehicle of the Chang'e-5T1 project separated from the service module, entered the atmosphere of the Earth, and made a soft landing in the Hoshune of Syzzyan Autonomous Region of Inner Mongolia.

February 18, 2016: the Chang'e-3 landing module continues to operate normally after 28 lunar days, exceeding the estimated and designed hardware lifetime.

December 14, 2016: The landing module "Chang'e-3" worked on the lunar surface for three years, which is a record period for the work of the descent vehicle on the lunar surface.

May 21, 2018: The Tseuqiao repeater satellite (forty-bridge) was launched from the Xichang Cosmodrome Chinese Cosmodrome, it is necessary for organizing the connection between the Earth and the far side of the Moon.

June 14, 2018: The Tseutsyao satellite relay went into halo orbit around the Earth-Luna Lagrange point L2, approximately 65,000 km from the Moon, becoming the world's first communications satellite operating in this orbit.

December 8, 2018: The Changzheng-3B launch vehicle with the Chang'e-4 station was successfully launched from the Xichang Chinese cosmodrome.

January 3, 2019: the Chang'e-4 descent vehicle lands in the Karman crater on the far side of the Moon. The Chang'e-4 landing gear contains the second Chinese moon rover, Yuytu-2, a modernized analogue of the Yuytu rover. The missions of the Chang'e-4 mission continue to operate normally.

2019-2020 year: The implementation of the Chang'e-5 mission is expected, the apotheosis of which is the delivery of at least two kilograms of lunar samples to Earth.



The lander of the mission "Chang'e-5T1" November 1, 2014 after landing in the autonomous region of Inner Mongolia:



The Chinese automatic interplanetary station for the study of the Moon and outer space “Chang'e-4” was successfully launched from Earth on December 7, 2018 (at 21:00 Moscow time, on December 8 at about 02:00 local time) by the “Changzheng 3B "from the Sichan Cosmodrome.

Photo launch "Chang'e-4":











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Thus, more than 60 years have passed since the first launch of the spacecraft on the Moon - the Soviet station Luna-1 in 1959.



Libration points of the Earth-Moon system:



Here are some interesting facts about the space lunar history and the Chang'e-4 mission from the mouths of the Chang'e project participants and the creators of its modules, gathered from three conversations of journalists from China Pictorial with scientists and engineers involved in the China Moon research program.

Ye Peijian is a research manager at the Chinese Academy of Space Technologies, a consultant to the chief designer and project manager of Chang'e.



Ye Peijian: “Having lived for more than 70 years, I have seen many ups and downs. But now I am very excited and proud. People have finally planted a spaceship on the far side of the moon. I was very lucky. Among the 7.5 billion people on Earth, the main team of the Chang'e-4 project consists of only a few hundred people. The opportunity to get into it is one of ten million. And we (my colleagues and I) got it. ”

Q: Were there any obstacles in the implementation of the three-year plan from 2001 to 2004, carried out according to the feasibility studies of the China lunar research program? What was the basis for the discussion and implementation of this program?

Ye Peijian: It was a rather complicated process. Due to limited funding, we had to achieve scientific goals and progress in developing elements of the lunar space research program with a minimum number of launches. Thus, we planned to divide the project of an unmanned exploration of the Moon into three stages - going into orbit, landing on the surface and returning to Earth. While developing this three-stage plan, there were no obstacles, but there were certain differences as to how to start the implementation of the first part.

Several options were presented and analyzed, but the research program proposed by the specialists of the Chinese Academy of Space Technologies was ultimately chosen for two main reasons.

Firstly, we could not borrow and use too many new technologies in our developments, which would be very risky, so we basically inherited the technologies of the two previous space programs and platforms - Dongfanghong-3 (Dongfang Hung-3) and the China Earth Resource Satellite-2.

Secondly, China was late in mastering the moon, so we needed to use advanced methods to speed up the project’s implementation and ensure its continued continuation after the completion of each stage. In general, in this project we have achieved a fairly good balance between inherited technologies and innovations.

An important lesson that China has learned from manned space flight and the Moon exploration program is the need to significantly think through every element of the project at the highest level. Throughout all three phases of our lunar explorations, we will stick to the plan and maintain the cohesion of our team.

We all adopted this philosophy: working on one stage, we consider how to use the technology used in the previous stage, as well as how to use the current accumulated experience in the next stage. This ensures that we continue to move forward, no matter how hard it is.

Question: After the start of the Chang'e project was launched in 2004, it took your team three years to complete the creation of the first Chang'e-1 satellite, which tasks were the most difficult in these three years?

Ye Peijian: When I took on the role of the chief designer of Chang'e-1, I took a huge responsibility because I was also the chief designer and developer of another satellite - China Earth Resources Satellite-2, the first Chinese satellite to observe the Earth's surface. As you know, Chang'e-1 was the first Chinese satellite to explore the moon, and for the first time we encountered many unprecedented technical problems, the solution of which was very difficult and difficult for us.

For example, how can a satellite accomplish a rapprochement with the Moon without attracting it to the surface under the action of gravity? We could not experiment on Earth to answer this question.

And how should we ensure communication with a satellite in the Moon orbit at a distance of almost 400,000 kilometers from Earth?

The organization of positioning on the moon requires UV sensors, but at that time in China there was no such technology, so we had to start developing them ourselves.

The satellite orbiting the Earth requires for its positioning data on the coordinates of two bodies, while the satellite of the Moon requires for its positioning data on the coordinates of three bodies, including the Earth, the Sun and the Moon, therefore its antenna must rotate. How could we implement this?

The temperature difference in the orbit of the moon can exceed 300 degrees Celsius, so how can satellite equipment survive this temperature gradient when the moon orbits?

There were many more questions. As a result, we summarized seven key technical problems and solved them one by one.

Question: What was your most stressful moment in the process of implementing the lunar research program?

Ye Peijian: I continue to think that we all deserve this success after all our efforts. If we did not succeed, perhaps we missed something. Our work on the Chang'e project was very scrupulous.

We have worked and taken into account the hundreds of emergency plans that may arise for the Chang'e-4 mission. We took into account all the problematic moments that we could imagine, and we have special procedures for certain actions for those employees who are in the monitoring post and make decisions when technical problems arise. However, there is no one hundred percent guarantee of success in any scientific experiment.

I witnessed the launch of each spacecraft of the Chang'e mission personally. As a key participant in the project, I always try to keep calm, so no one around and do not panic. If I look worried, people can expect trouble from this situation. At such a moment, I prefer a way of hanging out, like specialists in the mission control center, when they drink coffee and calmly communicate, and in fact nothing remains.

Question: How do you monitor the progress of the lunar research program and prevent potential risks?

Ye Peijian: Despite the success of the Chang'e-1 mission, the start of the second phase of the program (the launch of the Chang'e-2 mission) met with serious resistance. But should the Chang'e-1 satellite be China’s only successful attempt to reach the moon?

The development of the second satellite has already been completed, and there was little reason not to launch it in order to gain more experience in the future. Satellite Chang'e-2 successfully reached the Lagrange point L2 of the Earth-Sun system, which is 1.5 million kilometers from Earth, and also circled around the asteroid 4179 Tautatis and sent this photo:



Before the fourth lunar mission, some objected to the idea of ​​landing the Chang'e-4 on the opposite side of the moon. While the Chinese lunar exploration program continues, the far side of the moon will always remain the key to innovation.

If a chance comes, why waste it and spend more time and money in the future to do the same?

In the process of implementing the “Chang'e-4” mission, we faced many problems arising from the technical limitations that appear on the far side of the Moon. The most serious problem was the organization of communication. Therefore, we have previously launched a satellite relay.

The surface of the far side of the moon is replete with stones and craters, so the landing required the use of an array of special sensors to analyze the terrain and choose a safe landing site, which we also successfully completed.

Question: One of the goals of the Chang'e-4 mission is international cooperation in the field of scientific research, which was eventually provided by four international partners. What is your opinion about such cooperation?

E. Peijian: The moon is still far away and only a limited number of landings have been made on it, and scientists all over the world take every opportunity to conduct research there.

International cooperation fosters human development by demonstrating China’s openness to research.

Unfortunately, some international projects on the study of the Moon exclude the participation of China, but we do not seek to exclude anyone. All countries can take part in the construction of our lunar space station and in conducting lunar explorations.

American scientists have proposed to increase the operating time of the Chinese lunar satellite transceiver "Tseyutsyao" to five years. They hope to use this satellite, and we also welcome it.

Question: What are the goals of studying the moon?

Ye Peijian: Was the moon a part of the earth? Or did it originate simultaneously with the Earth? Tips for answering this question have not yet been found.

Exploring the moon can improve our understanding of the formation of the universe. The moon is also rich in resources. For example, the regolithic helium-3 deposits on the moon can be used to generate energy.

According to calculations, the supply of helium-3 on the moon could be enough for humanity for 10,000 years. The difficulty is in how to use its reserves on the moon or ship to earth. At the moment, this may seem technically difficult, but what about a century or two? It is not available now, but it will not necessarily be available in the future.

Q: Tell us about the dynamics of China’s deep space exploration programs compared to other countries?

E Peijian: Moon exploration restored the popularity of space programs in the 21st century. But we do not expect China to achieve remarkable new results in a short time. Our efforts have paid off, but overall we are still lagging behind other countries in this area.

Our goal is to deliver samples from the moon back to Earth this year or the beginning of the next.

We are also developing a project to send our Taikonauts to the Moon, and plan to visit the South and North Lunar Poles. In the foreseeable future we will lead in the exploration of the moon.

According to our plan, the Mars-1 station will be launched in 2020. Its goal will be not only the entry into the orbit of Mars, but also the landing of the 240-pound rover. In September 2018, Chinese engineers carried out successful parachute statosphere tests, which will be used to quench the landing speed of the Martian descent vehicle.

If the plan succeeds, then China will be one step ahead in exploring Mars. We also plan to explore asteroids and reach Jupiter by the 100th anniversary of the founding of the People's Republic of China. Only after these steps are completed, will China take a leading position in the development of deep space.

Temperature tests of the Chang'e-4 descent vehicle:



The most important work is the installation of the “national flag” element:



Zhang He - executive director of the Chang'e-4 project: This part of the picture and icons on monitors is



interesting : Zhang He: “The study of the far side of the moon has always been a dream for scientists around the world. Pictures sent by the descent vehicle "Chang'e-4" and the rover "Yuytu-2" represent a completely different picture of the far side of the moon than we imagined. In addition, the analysis of the results of lunar studies of the visible and reverse sides of the moon can lead to new scientific discoveries, which will be of great importance to scientists and engineers around the world.

Question: From takeoff to landing, when were you most nervous? What do you think was the most important factor in the success of the Chang'e-4 mission?

Zhang He: Three things made my heart stop. The first point was the launch of the rocket, the launch of the device into the correct orbit and the deployment of solar panels for energy supply.

The second point was the phase of space braking. If "Chang'e-4" had not slowed down when approaching the Moon, then it would have flown past it and carried off into space. Thus, its speed and position should have been precisely controlled. Otherwise, he would not even be able to rotate around the moon in the required orbit.

The last but most nervous moment was the slow descent process and landing procedure. Unlike the control of the Chang'e-3 modules, the telemetry from the Chang'e-4 comes from the Tseuqiao satellite transponder, which results in a delay of two to three minutes. This eliminates any possibility of quickly changing the direction of motion from the Earth. Thus, the entire landing process was automated and it was not possible to remotely control this procedure.

Each landing support of the “Chang'e-4” descent module has a sensor for touching the surface. When we saw that all four sensors worked off the touch, and also received the first image from the camera of the descent module, we realized that Chang'e-4 had finally landed on the Moon. The next task was to automatically open the solar panels. After its completion, we realized that we had avoided the most dangerous problems at this stage of the mission, and felt relieved.

Very dug in comparison with the visible side, the reverse side of the moon is full of craters. Therefore, in contrast to the Chang'e-3, we adjusted the landing procedure and made many changes to the software of the Chang'e-4 landing gear for automatic control. The descending module "Chang'e-3" was decreasing in an arc when landing on the moon. The landing module "Chang'e-4" first moved horizontally, at the same time slowing down, and then, having reached a height of six kilometers above the planned landing platform, descended to the landing site almost vertically to avoid possible obstacles.

Operators on Earth could follow the landing of the Chang'e-3 with a very short time delay. Communication with the landing module "Chang'e-4" required much more time, so we could not quickly respond to possible failures during landing in real time. Thus, the landing module "Chang'e-4" worked in the automatic mode, controlling the modes of the engines and receiving data from the onboard sensors.

Question: Tell us about possible problems and obstacles during scientific research that the Chang'e-4 lander and the Yuuta-2 rover on the far side of the Moon may encounter? What are the biggest discoveries they can make?

Zhang He: Since the evolution of the reverse and visible sides of the moon is quite different, we hope that the Chang'e-4 project will help make new discoveries based on the analysis of surface material (soil) on the back of the moon, which is carried out using an infrared spectrometer installed on a rover Yuytu-2.

Also, the Yuuta-2 rover is equipped with an electromagnetic radar. This radar sends electromagnetic pulses that pass through the lunar soil and are reflected from the formations under the lunar surface, allowing you to gather information about the layered structure of the lunar crust. We hope that the “Yuytu-2” rover will move further, scanning as much space as possible.

The most difficult part of the project at this stage is to conduct low-frequency radio astronomical observations of the Universe, the Sun and other celestial bodies. These observations are complicated by the fact that the Chang'e-4 modules also emit many low-frequency electromagnetic signals.

According to the data we have already received, there is still a lot of work to be done to remove interference from them and to emit low-frequency radio signals from the Universe, especially from the Sun.

Question: What is the biggest difference between the modules of the Chang'e-3 and Chang'e-4 projects?

Zhang He: The two lander apparatus Chang'e-3 "and" Chang'e-4 "look the same, but in the filling they are completely different.

Firstly, since the Chang'e-4 guided landing navigation strategy is different from the Chang'e-3 landing procedure strategy, all navigation sensors, distance measuring sensors and speed sensors have been specially modified for use when landing on the far side of the Moon.

The second difference is the collection of data on surface and ground temperatures during the moonlit night, which was not possible in the Chang'e-3 project.

In the Chang'e-4 project, modern technological advances are used to solve the problem of continuous powering the device for measuring temperature during a moonlit night, when the main components of the modules are in "sleep mode".

The Chang'e-4 descent module is capable of measuring the temperature of the soil beneath it at several points, as well as receiving other data.

Question: What is your most vivid memory of the work on the Chang'e-4 project?

Zhang He: Participating in the lunar research program gave me more courage to solve complex problems, I became more competent in many technical issues.

When I first started working in the Chang'e project, I once participated in engine testing. At some instant, the sound of engine elements squeaking became very loud, this situation put me off balance, and I began to get very nervous. My colleagues reassured me, saying: "It will take some time, and you will get used to it." The time has passed, and now I am used to much.

On another occasion, during a mechanical experiment, I again encountered an amplifying sound, as if the entire satellite began to resonate in a different frequency band. When this huge noise surrounded me, I stopped being nervous and worried that something had gone wrong with the project.
It was a tough exercise on my mental stamina. By performing more of these exercises, I tend to believe that any problem can be solved no matter how difficult it is.

I was obsessed with the love of the stars since childhood, and took many photos of celestial bodies. I dream to develop further and see more extraterrestrial celestial bodies. Therefore, I am very lucky that my work is directly related to comic research and I am a member of the Chinese team of lunar researchers.

Jia Yang , Deputy Chief Designer of the Lander Chang'e-4 and designer of the Chinese Lunar Rover Yuytu.

Question: It is true that the Chang'e-4 mission was originally planned as a backup for the Chang'e-3 mission. Why, then, “Chang'e-4” was sent to a dangerous solitary mission on the far side of the moon, and not “united” with its predecessor according to the scenario already worked out?

Jia Yang: Several possible routes were planned for the Chang'e-4 mission, including landing near the Chang'e-3 landing site. But in the end we decided to land the Chang'e-4 on the far side of the moon. The reason this decision was made was simple: although humanity explored the moon many times, an automatic landing on the far side of the moon would be an unprecedented feat.

Question: If there is no evidence of aliens or alien spacecraft on the far side of the moon, what then is there that attracts scientists so much?

Jia Yang: The moon is an ancient celestial body. She was active three billion years ago, but now there is calm. Landing on the back of the moon gives us clues about its evolution, which greatly contributes to the study of the early history of the moon and the earth.

Question: The moonlit night lasts two weeks, how in this period does the Chang'e-4 lander and the Yuytu-2 lunar rover function in complete darkness?

Jia Yang: Without a solar energy on a cold moonlit night, the landing gear and rover lose their energy and go to sleep. In this cold time, the special internal elements of the modules emit heat, which helps them survive the night.

Question: Why was the Yuuta-2 rover designed as a six-wheeled all-terrain vehicle, and the tracks were not used? If the “Yuuta-2” rover falls over, can it restore its position?

Jia Yang: The wheel elements of the Yuuta-2 rover are indeed its complex design feature, which had to be refined for a long time at the design stage. We refused to use the tracks because they were less maintainable and vulnerable on tests.

For example, if a small stone gets inside the caterpillar's mechanism, the rover can get stuck and lose its course. Unlike wheeled sales, which is more reliable and has an increased resource, and can safely move stones up to 20 centimeters high.

However, if the “Yuuta-2” rover turns over, it will not be able to return to the working position again. The solar panels on the sides of the lunar rover are very fragile, they can crack or become covered with dust after a fall, which will make them unusable.

Thus, we focused on maximally keeping the position of the “Yuuta-2” rover in a stable condition and not allowing it to fall when moving over the surface.

Question: Is it possible to transmit a live broadcast from the surface of the back side of the moon with the help of the Tieuqiao satellite transponder?

Jia Yang: This is theoretically possible, but the current communication channels cannot meet the requirements for streaming live video.

Question: How long will the Yuuta-2 rover work on the moon? How far can he get?

Jia Yang: His estimated life expectancy is about three months, the range of up to 10 km. He already drove more than his predecessor rover "Yuytu".

It is difficult to say how long he will travel in two months, but for a lunar day he now travels no more than 50-80 meters, it makes no sense to drive him across the surface, since the surface of the moon is not a highway, but a place for scientific research. But we hope that his resource will last for another few months.

Question: Are the tracks of the “Yuytu-2” rover forever on the moon?

Jia Yang: It depends on what you mean by "forever." For example, marks on the surface of the moon from its wheels will remain at least hundreds of thousands of years.

Question: What data can the Yuuta-2 rover send back to Earth from the far side of the moon?

Jia Yang: the Yuytu-2 rover is equipped with scientific tools for geophysical study of the lunar surface, including soil stratification, soil temperature, analysis of mineral elements, and so on.

Question: How far apart are the two Chinese moon rovers? Is it possible for them to meet? Will new rovers be sent to the "Yuytu" on the moon?

Jia Yang: Two lunar rovers "Yuytu" and "Yuytu-2" are respectively on the visible and reverse sides of the moon, at a very large distance from each other. They are not destined to meet in any way. I very much hope that in the future there will be more Yuytu rovers on the Moon and on other celestial bodies.

Assembling elements of the “Yuytu-2” rover at the Chinese Academy of Space Technologies:



Rover “Yuuta-2” in testing at the Chinese Academy of Space Technologies:



Workers are checking the elements of the “Yuuta-2” rover in the assembly hall:



Photo of the lunar surface near the rover:



Rover presentation in Beijing August 15, 2018: