In January this year, China's lunar exploration program celebrated its 20th anniversary. Time flies, 20 years of time like a white horse, China's lunar explorers continue to work hard and innovate, so far they have successfully completed the three-stage strategic goal of "lunar exploration, lunar exploration, and sample return exploration" (referred to as "orbiting, falling, and returning"), and began to implement the fourth phase of the lunar exploration project.
Each phase of the lunar exploration project is a deepening of the previous stage and lays the foundation for the next stage. Today, we invite Pang Zhihao, the chief science communication expert of the national space exploration technology, to talk about the important achievements of China's lunar exploration and what these scientific research achievements will bring to mankind's future journey to the moon.
Deep space exploration has officially begun.
Chang'e-1: Take a real "image of the whole moon".
The first image of the lunar surface sent back by Chang'e-1 was officially released by the China National Space Administration on November 26, 2007.
On January 23, 2004, China's lunar exploration program was approved and named "Chang'e Project". The first phase of the lunar exploration project was completed through the launch of a probe around the moon, marking the beginning of China's aerospace expedition to deep space exploration.
On October 24, 2007, China's first lunar probe, the Chang'e-1 lunar probe, was sent into space by a Long March-3A rocket. On November 20, 2007, it sent back the first image of the lunar surface, thus setting up the third milestone in China's aerospace industry after the Dongfanghong-1 artificial earth satellite and the Shenzhou-5 manned spacecraft.
On July 1, 2008, Chang'e-1 completed the acquisition of all-lunar image data, and since then has carried out more than 10 verification tests such as orbit change. Chang'e-1 has flown a total of 494 days, including 482 days around the moon, 117 days more than originally planned; 3 lunar eclipses during the flight; Pass back 137TB of valid scientific detection data; A number of scientific research results have been obtained, such as the whole lunar image, the distribution of chemical elements on the lunar surface, the mineral content on the lunar surface, the distribution of lunar soil and the near-moon space environment, which have filled the gap in the field of lunar exploration in China.
Compared with artificial earth satellites, Chang'e-1 uses more new technologies, such as orbit design, three-body orientation, temperature control and ultraviolet sensor. It is equipped with 8 kinds of scientific instruments, including CCD stereo camera, laser altimeter, interferometric imaging spectrometer, ray spectrometer, X-ray spectrometer, etc., and for the first time in the world, a microwave detector is used to measure the microwave radiation characteristics of the moon, invert the thickness of the lunar soil, and estimate its helium-3 distribution and resources. Among them, the CCD stereo camera carried by Chang'e-1 has achieved 100% coverage of the lunar surface for the first time in the world, making the "whole lunar image map" produced by China at the international advanced level in terms of geometric registration accuracy, data integrity and consistency, and image tone.
In order to "explore the path" of the second phase of the lunar exploration project and accumulate experience in the control of the lunar landing process and orbit determination, Chang'e-1 made a controlled impact on the rich sea area of the moon on March 1, 2009, and the lunar journey was successfully completed.
The journey to the moon breaks through key technologies.
Chang'e-3: The first landing was a success.
In December 2013, the Yutu lunar rover photographed the Chang'e-3 lander with a panoramic camera on the lunar surface.
From the point of view of the directness and richness of the acquisition of exploration data, soft landing exploration and patrol survey are irreplaceable by other forms of exploration, so lunar landing exploration is very important.
The main task of the second phase of China's lunar exploration project is to carry out lunar exploration, which was completed by the successive launches of Chang'e-2 and Chang'e-3. Therefore, in order to reduce the risk of lunar exploration, China launched the first lunar probe Chang'e-3 on October 1, 2010 before launching the first lunar probe Chang'e-3. It has carried out high-resolution imaging of the pre-selected landing area of Chang'e-3, and has also obtained richer and more accurate exploration data, deepening the scientific understanding of the moon.
On April 1, 2011, after the expiration of the half-year design life of Chang'e-2, a number of extended experiments were carried out, creating a precedent for China's aerospace to carry out multi-target and multi-mission exploration of the moon, Lagrange 2 points and asteroids through a single launch, making China the third country in the world to visit 2 Lagrange 2 points and the fourth country to explore asteroids.
With Chang'e-2, the successful pioneer, the lunar journey of Chang'e-3, the main mission of the second phase of China's lunar exploration project, will be much smoother. On December 2, 2013, the Chang'e-3 lunar probe was directly sent into the Earth-Moon transfer orbit, and then made a soft landing on the lunar surface on December 14, achieving China's first soft landing on a celestial body outside the Earth. On December 15, the Chang'e-3 lander and the Yutu lunar rover took pictures of each other, and China became the third country in the world to master the technology of lunar exploration.
Chang'e-3 is composed of a lander and a rover (that is, the Yutu lunar rover), so the launch of Chang'e-3 is actually a two-month probe, which can carry out in-situ exploration and roving exploration respectively, which is the first time in the world.
In order to complete the engineering task, Chang'e-3 has passed the landing pass, the patrol pass and the moonlit night survival pass. Especially in the process of landing on the lunar surface, the Chang'e-3 lander carrying the Yutu lunar rover used a 1500-7500 N variable thrust engine (which is a key technology that many countries do not have) and a landing camera to overcome the three major technical difficulties of thrust reverser deceleration, autonomous control and landing buffer, and safely landed in the area east of the moon's Hongwan when landing on the moon. The intelligent landing technology of hovering and obstacle avoidance adopted by it is at the international advanced level. The Chang'e-3 lander carried four payloads, including a topographic camera, a landing camera, an extreme ultraviolet camera, and a moon-based optical telescope. The Yutu lunar rover carries four payloads: a panoramic camera, a lunar radar, an infrared imaging spectrometer, and a particle excitation X-ray spectrometer. Among them, extreme ultraviolet cameras, moon-based optical telescopes, and lunar radars are all used for the first time in the world in lunar surface exploration.
Until now, it is still a difficult problem to carry out lunar exploration, which has led to the failure of many countries, and at that time, China's Chang'e-3 successfully landed on the moon with its excellent technical level, laying a solid foundation for the subsequent landing of Chang'e-4 and Chang'e-5. Today, Chang'e-3 has carried out scientific explorations of "lunar survey", "sky survey" and "earth observation", and has obtained a large amount of scientific data, and its lander is still working on the lunar surface, which is currently the longest working lander on the lunar surface in the world.
Sample returns make history.
Chang'e-5: Four "firsts" to greatly improve space technology.
The main task of China's lunar exploration phase III project is to complete the unmanned lunar sample return mission through Chang'e-5, which is conducive to further understanding the status of the moon, material content and other important information, deepening the understanding of the formation and evolution of lunar soil, lunar crust and lunar base, and providing data for future manned lunar landing and lunar base site selection.
The Chang'e-5 returner needs to re-enter the atmosphere at close to the second cosmic velocity, which is technically complex. Because the reentry speed of the returner is doubled, the reentry heat will be increased by a factor of 8 to 9, so the returner can easily burn out if the reentry is returned directly at a speed of about 11 km/s. In order to reduce the engineering risk, China launched Chang'e-5 T1 on October 24, 2014 to master the technology of ultra-high-speed re-entry and re-entry into the atmosphere. Chang'e-5 T1 consists of two parts: a service module and a returner, and its returner is basically the same as that of Chang'e-5. After liftoff, they first flew near the moon, then automatically returned to Earth, and finally, their returner re-entered the atmosphere at a semi-ballistic jump close to the second cosmic velocity on November 1 of the same year, and successfully landed in a predetermined area of Inner Mongolia.
The so-called "semi-ballistic jump re-entry" means that after entering the atmosphere, the spacecraft relies on lift to rush out of the atmosphere again to slow down and consume energy, and then enters the atmosphere again. In other words, it is to re-enter the atmosphere by "playing the water", and "one out and one in" in the atmosphere, which can extend the trajectory of the returner in the atmosphere, consume part of the energy, and reduce the landing speed. This is the first time that China's spacecraft has re-entered and returned to the earth after flying around the moon, indicating that China has broken through and mastered the ultra-high-speed re-entry and return technology of spacecraft, and has also made China the third country in the world to successfully launch a spacecraft around the moon.
On November 24, 2020, the Chang'e-5 sample returner, which consists of four parts: an ascent, a lander, an orbiter, and a returner, was launched. After overcoming a series of difficulties, the Chang'e-5 returner successfully returned to Earth on December 17 of that year with 1,731 grams of lunar samples, making China the third country in the world to return to Earth with lunar samples, and at the same time, it also drew a successful end to the strategic planning of the three stages of China's lunar exploration project.
From launch to return, Chang'e-5 has undergone a total of 23 major orbital controls and 6 major separation controls, as well as a number of high-risk links such as power descent and lunar takeoff, rendezvous and docking. In order to complete the lunar sample return mission, Chang'e-5 has achieved four "firsts" since China launched space activities, which has greatly improved space technology.
The first is the first automatic sampling on the lunar surface. When collecting samples on the lunar surface, the sampling device on the lander needs to have the ability to drill, shovel and transport in the moon's low-gravity environment, and encapsulate after the sampling is completed, without any contamination in the process. Thanks to the preparation, the task, which would have taken two days, was completed in just 19 hours.
The second is the first take-off from the lunar surface. After the collected samples are encapsulated to the ascent, the ascent will take off from the lander, which is the first time that China's space vehicle has taken off on an extraterrestrial object, which is very difficult. If the flame ejected from the ascent vehicle takes off hits the lander, it can create a distraction factor. However, facts have proved that sufficient preliminary preparations and technical support have enabled the take-off from the lunar surface to be completed smoothly.
Third, for the first time, unmanned rendezvous and docking were carried out in lunar orbit 380,000 kilometers away. For the first time in the world, the ascender carrying lunar samples will enter lunar orbit and dock with the orbiter-returner assembly there for unmanned rendezvous and docking, and transfer the collected samples to the returner. To this end, China has developed a space light and small weak impact docking mechanism called the claw-holding type, which is installed on the orbiter, thus completing this task.
Fourth, for the first time, it returned to Earth with lunar soil at a speed close to the second cosmic speed. Finally, the Chang'e-5 lunar sample returner re-entered the atmosphere at a speed of about 11 kilometers per second, although China has tested it with Chang'e-5 T1, but the Chang'e-5 return is a real combat test, and the results are very satisfactory.
It is worth mentioning that only the Soviet Union had carried out 3 unmanned lunar sample returns in the 70s of the 20th century, but only brought back a total of 330 grams of samples, because the Soviet Union did not master the unmanned rendezvous and docking technology in lunar orbit at that time, and the ascender returned directly to the earth, which needed to overcome the dead weight of the returner and a large amount of fuel.
For the first time, Chinese scientists have stored, analyzed and studied self-taken lunar samples, and have achieved many scientific research results, such as revealing that magmatic activity still existed on the moon 2 billion years ago; A new mineral on the moon was discovered, named "Chang'e", which is also the sixth mineral in the world that is not found on Earth.
The fourth phase of Lunar Exploration is off to a good start.
Chang'e-4: Explore the far side of the moon and trace the history of the planet.
In 2019, the Chang'e-4 lander's topographic camera took a panoramic view (cylindrical projection).
From the perspective of the strategic objectives of the three stages of "orbiting, falling, and returning", they have an obvious progressive relationship: the orbiting exploration mainly conducts a global comprehensive survey of the moon; The lunar landing exploration is mainly a regional detailed investigation near the landing area, including in-situ exploration and roving exploration, which is relatively complex. Sample return exploration is mainly a regional precision survey of the moon, and scientists can conduct detailed studies of the collected lunar samples in the laboratory, which is the most complex and difficult.
At present, China has begun to implement the fourth phase of the lunar exploration project, and takes Chang'e-4 as the first mission of the fourth phase of lunar exploration, that is, to carry out soft landing and roving exploration on the far side of the moon. Because the far side of the moon is more primitive than the front, it is of great value for studying the early history of the moon and the earth. In addition, since the far side of the Moon will never be seen from the Earth, it is possible to detect cosmic low-frequency radio signals that cannot be distinguished from the Earth's orbit due to interference on the far side of the Moon, and it is expected that major astronomical results will be achieved.
However, because the far side of the Moon is never visible from Earth, a probe landing on the far side of the Moon cannot directly communicate with an earth station. To this end, on May 21, 2018, China launched the world's first lunar relay satellite "Queqiao" in the Earth-Moon Lagrange 2-point halo orbit. The "Queqiao" operating in this orbit can "see" the Earth and the far side of the Moon at the same time, thus providing a communication link between Chang'e-4, which will later fall on the far side of the Moon, and the earth station, transmitting TT&C communication signals and scientific data.
On December 8, 2018, China successfully launched the Chang'e-4 lunar landing probe, which completed a soft landing on the far side of the moon von Kármán impact crater on January 3, 2019, which is also the first time in the world.
As a backup to Chang'e-3, Chang'e-4 still consists of a lander and a rover (Yutu-2 lunar rover), but because the scientific objectives of Chang'e-4 and Chang'e-3 are very different, the scientific payload carried by the two has changed significantly. The Chang'e-4 lander is still equipped with a landing camera and a topographic camera, but the newly developed low-frequency radio spectrum analyzer and the German lunar surface neutron and radiation dose detector have been added, and the moon-based optical telescope and extreme ultraviolet camera mounted on Chang'e-3 have been removed. The Yutu-2 lunar rover is still equipped with a panoramic camera, a lunar radar, and an infrared imaging spectrometer, but the Swedish neutral atom detector has been added and the particle excitation X-ray spectrometer has been removed.
Chang'e-4 has also been greatly improved in terms of performance. Since the landing area of Chang'e-3 is equivalent to the relatively flat North China Plain on Earth, and the landing area of Chang'e-4 is equivalent to the Yunnan-Guichuan region with lofty mountains, Chang'e-3 landed slowly in an arc trajectory, while Chang'e-4 landed almost vertically. Chang'e-3 could not work in the environment of Changyueye-180, and Chang'e-4 adopted a new energy supply method - isotope temperature difference power generation and thermoelectric comprehensive utilization technology, which can ensure that it can survive the cold and long moonlit night and carry out normal detection work, so the temperature of shallow lunar soil during the moonlit night was measured.
At present, the Chang'e-4 lander and the Yutu-2 lunar rover are still in "overdue service", of which Yutu-2 is currently the world's longest lunar rover working on the lunar surface.
Work together to build an international lunar research station.
Manned moon landing: from the moon for a thousand years to the moon in one day.
In the future, China will launch Chang'e-6, Chang'e-7 and Chang'e-8, and eventually establish a lunar scientific research station and achieve a manned landing on the moon.
This year, Chang'e-6 will make breakthroughs in key technologies such as the design and control of the moon's retrograde orbit, intelligent sampling on the back of the moon and take-off and ascent on the far side of the moon, carry out automatic sampling and return on the far side of the moon, and carry out scientific exploration and international cooperation in the landing area, and carry out 10 kg international payload. This year, China will also launch the Queqiao-2 lunar relay satellite to replace the "Queqiao" that has been "overdue".
Chang'e-7, which consists of an orbiter, a lander, a rover, and a spacecraft, plans to land at the south pole of the moon in 2026 to conduct a detailed survey of the environment and resources of the south pole of the moon, including the detection of the age of the lunar soil at the south pole of the moon and the isotope composition of hydrogen, carbon, helium and oxygen in the solar wind. Among them, the orbiter will be equipped with five scientific payloads, including a high-resolution stereo camera, a lunar microwave imaging radar, a wide-band infrared spectral imaging analyzer, a lunar neutron gamma spectrometer, and a circumlunar magnetometer. The lander will be equipped with four scientific payloads, including a lunar surface environment detection system, a lunar seismograph, a landing camera, and a terrain and landform camera. The rover will be equipped with five scientific payloads, including Raman spectrometer, lunar radar, lunar surface magnetic field measuring instrument, panoramic camera, and lunar soil volatile matter measuring instrument. The spacecraft will be equipped with a scientific payload lunar soil water molecule analyzer, which will be directly connected to the spacecraft platform.
Chang'e-8 is scheduled to be launched around 2028, and it will be composed of a lander, a spacecraft, a rover, and a lunar surface operation robot, and will land near Chang'e-7 to form a basic lunar scientific research station with it, and test and verify some key technologies for the utilization of lunar resources, such as the use of lunar soil in-situ 3D printing technology. It is expected that by 2040, China will also cooperate with Russia and other countries to build a complete international lunar scientific research station, and then build an applied lunar scientific research station.
The most remarkable thing for the world is that China will implement a manned landing on the moon before 2030. To this end, aerospace experts are carrying out a series of scientific research projects, including the development of a new generation of manned carrier rocket, the Long March 10, a new generation of manned spacecraft, a lunar lander, a manned lunar rover, and a lunar landing suit.
In the past 20 years, from orbiting the lunar racket**, to the world's first spacecraft landing on the far side of the moon, and then to successfully bringing back the moon's "native products", the three-step strategy of "orbiting, falling, and returning" has come to a successful conclusion. Today, the lunar explorers are still walking non-stop, and the Chinese, who have been looking at the moon for thousands of years, will eventually use modern aerospace technology to realize the dream of taking the moon in nine days.
Further reading] Memorabilia of China's 20 years of lunar exploration.
In 2004, China launched the lunar exploration project, which was listed as one of the 16 major projects in the Outline of the National Medium and Long-term Science and Technology Development Plan (2006-2020). According to the principle of step-by-step, distributed implementation and continuous leapfrogging, the project is divided into three development stages of "winding, falling and returning", and will be completed in 2020.
On October 24, 2007, the Long March-3A carrier rocket successfully launched the Chang'e-1 lunar probe from the Xichang Satellite Launch Center.
On November 12, 2008, the "Orthophoto Map of the Whole Moon of China's First Lunar Exploration Project" produced by the data taken by Chang'e-1 was released, which was the most complete image of the moon published in the world at that time.
On October 1, 2010, the Long March-3C carrier rocket successfully launched Chang'e-2. Chang'e-2 is the technical pilot satellite of Chang'e-3 lunar exploration, which is mainly used to test and verify some new technologies and equipment to reduce the risk of subsequent lunar and deep space exploration.
On June 9, 2011, Chang'e-2 left the moon after completing the established six major engineering goals and four major scientific exploration missions, and then arrived at 2 o'clock in the Sun-Earth Lagrange, setting a new record for China's space tracking and control distance, and also becoming the world's first spacecraft to go directly from the Moon to 2 o'clock in the Sun-Earth Lagrange.
On December 2, 2013, the Long March-3B carrier rocket successfully launched the Chang'e-3 lunar probe, the main mission of the second phase of the lunar exploration project. On December 14, the Chang'e-3 lander and China's first lunar rover, Yutu, made a successful soft landing in the Hongwan landing area in the northwest of the Lunar Rain Sea.
On October 24, 2014, China launched Chang'e-5 T1 to master the technology of ultra-high-speed re-entry and re-entry into the atmosphere and prepare for the launch of Chang'e-5.
On May 21, 2018, the Queqiao lunar relay satellite was launched. It is the world's first communication satellite operating at 2 points of the Earth-Moon Lagrange, and undertakes the information relay mission between the Earth and Chang'e-4, which will land on the far side of the Moon.
On December 8, 2018, the Long March-3B carrier rocket successfully launched the Chang'e-4 lunar landing probe to carry out the main mission of the third phase of the lunar exploration project. On January 3, 2019, Chang'e-4 autonomously landed on the far side of the moon, achieving the first soft landing of a human probe on the far side of the moon.
On November 24, 2020, the Chang'e-5 sample returner was launched by a Long March 5 carrier rocket and successfully landed north of the Lumke Mountains in the Lunar Front Storm Ocean on December 1.
On December 17, 2020, the Chang'e-5 returner successfully returned to Earth with 1,731 grams of lunar samples, making China the third country to achieve lunar sample return.
In January 2024, the Chang'e-6 mission probe of the fourth phase of the lunar exploration project was delivered to the Wenchang Cosmodrome, and various pre-launch test preparations will be carried out as planned.
*: Beijing ** client Reporter: Wang Dan.
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