Chang'e 6 returns from "digging soil"! Who is on the back of the moon?

At 14:07 on June 25, the Chang'e-6 returner carrying humanity's first sample from the far side of the moon landed precisely in Siziwang Banner, Inner Mongolia, and the mission was a complete success.

The Chang'e-6 mission went through 11 stages, like a carefully planned space adventure.

According to preliminary calculations, the Chang'e-6 mission collected 1,935.3 grams of samples from the far side of the moon. After the samples were safely transported to the lunar sample laboratory of the National Astronomical Observatory of the Chinese Academy of Sciences, researchers from the ground application system will carry out the storage, preparation and processing of the lunar samples as planned and start scientific research.

The 11 phases of the Chang'e-6 mission

The Chang'e-6 mission is the most technologically advanced lunar exploration mission in China's space history to date. It has achieved "three major technological breakthroughs" and "one world first" , namely, breakthroughs in the design and control technology of the lunar retrograde orbit, the intelligent sampling technology on the far side of the moon, and the take-off and ascent technology on the far side of the moon. It has achieved the world's first automatic sampling and return on the far side of the moon , once again setting a world record for China's space program.

What is on the far side of the moon?

Lunar exploration is the first step for humans to step out of the cradle of the Earth and into the vast universe. Did you know that the soil on the front and back sides of the moon are significantly different in terms of geological structure and material composition? So far, humans have returned 10 lunar samples, but all of these samples were from the front side of the moon .

Due to the long-term influence of the Earth's gravity, the geological activities on the front side of the moon are relatively active, forming numerous impact craters and mountains. However, due to the less influence of the Earth's gravity, the geological activities on the back side of the moon are relatively weak, preserving a large amount of ancient geological information.

A handful of lunar soil, a galaxy of thousands of years

The reason why the team chose to land in the South Pole-Aitken Basin on the far side of the moon is that it has rich scientific value. The South Pole-Aitken Basin is the largest, deepest and oldest basin discovered on the moon . Studying the geological structure, material composition and evolution history here will help us understand the geological evolution history of the moon and even the early earth.

By studying lunar samples from this area, scientists hope to uncover the mystery of the early evolution of the moon and even the solar system.

According to information revealed by Hu Hao, chief designer of the Chang'e-6 mission, during the sampling process, Chang'e-6 felt that the lunar soil on the far side of the moon was different from that on the near side. The lunar soil on the near side was more delicate, while the lunar soil on the far side was more viscous and clumpy. This detail once again proves the differentiation of the lunar samples of Chang'e-6, and also shows that they are of high value.

How to "dig soil" on the back of the moon?

In order to fly to the far side of the moon, Chang'e 6 must first enter the Earth-Moon transfer orbit with a perigee of 200 kilometers and an apogee of about 380,000 kilometers. Digging on the far side of the moon faces many difficulties, including communication, terrain and landing, measurement and control, environment and technology .

Difficulty communicating

Since the moon's rotation period and revolution period are the same length, the moon always faces the earth with the same side. Due to the obstruction of the moon itself, the back side of the moon cannot communicate directly with the ground tracking and control station, so relay communication support is required through the Queqiao-2 relay satellite.

Rough terrain

The terrain on the back side of the moon is mainly highlands, covered with impact craters, and the terrain is relatively rugged. There are no large flat areas and terrain, which may cause problems such as lighting and measurement and control obstruction to probes in the landing area.

Harsh environment

The environment on the back of the moon is extremely harsh, with extremely low temperatures and strong radiation, which places extremely high demands on the performance and stability of the probe.

From June 2 to 3, Chang'e-6 successfully completed intelligent rapid sampling in the South Pole-Aitken Basin on the far side of the moon, and packaged the precious lunar far side samples and stored them in the storage device carried by the ascender, completing the "packing and boxing" of this cosmic express .

Chang'e-6 uses rapid and intelligent sampling technology to shorten the effective working time of lunar surface sampling to less than 20 hours. At the same time, the probe has withstood the test of temperature differences on the far side of the moon and overcome difficulties such as measurement and control, lighting, and power supply. It has collected lunar samples through drilling with drilling tools and surface sampling with a robotic arm .

Drilling sampling

Table sampling

The Chang'e-6 lander is equipped with a variety of payloads, including a landing camera, a panoramic camera, a lunar soil structure detector, and a lunar mineral spectrometer, which are all powered on normally, serving the detection and research of the lunar surface morphology and mineral composition, the detection of the lunar shallow structure, and the analysis of the underground lunar soil structure in the sampling area.

This full-body photo of Chang'e-6 on the back of the moon was taken by a camera robot that accompanied the Chang'e-6 on the moon.

After Chang'e-6 completed sampling on the far side of the moon, the small robot autonomously separated to the lunar surface, moved to a suitable shooting position, selected shooting angles and composition, and intelligently optimized the imaging position, ultimately capturing a third-person perspective image of the lander-ascender combination on the far side of the moon.

The ground can tell it instructions through Wi-Fi, but if there is no need, it can be completely autonomous, just like a very independent "child".

How to get home after digging?

Chang'e-6 is about 7.2 meters tall and consists of four parts: an orbiter, a returner, a lander, and an ascender. It weighs more than 8 tons in total, which is 100 kilograms heavier than Chang'e-5.

In the re-entry mission, Chang'e-6 adopted the "high-speed semi-ballistic jumping re-entry technology solution", commonly known as "skipping stones in space."

After Chang'e-6 successfully completed the sampling work on the far side of the moon, the ascender separated from the lander and took off, entering the ascending target orbit with a perigee of 15 km and an apogee of 180 km. After the sub-orbital maneuver, the ascender entered a circumlunar orbit at an altitude of 210 km. When the ascender was about 50 km in front of the orbiter-retrograde assembly and about 10 km above it, the orbiter-retrograde assembly began to actively approach and capture the ascender.

After completing the rendezvous and docking, the ascender will transfer the lunar soil samples to the returner. When flying to an altitude of about 5,000 km above the earth, the returner and the orbiter will unlock and separate, enter the tracking range of the high-speed loading return tracking measurement chain, and the orbiter will perform evasive maneuvers.

At an altitude of 120 km, the returner has reached the second cosmic speed, and it bounces back into the atmosphere and lands at the Siziwang Banner landing site in Inner Mongolia, completing a 53-day round trip from the Earth to the Moon. This process is just like skipping stones by the river when we were kids, hence the name "skipping stones".

This unique motion trajectory greatly reduces the overload that the spacecraft endures during the return process, thereby effectively ensuring the safety of instruments and personnel.

The successful landing and sample return of Chang'e-6 not only marks a new milestone in China's lunar exploration program, but also provides a new perspective and idea for human exploration of the moon and deep space. Let us look forward to more surprises and discoveries from Chang'e-6 and subsequent lunar exploration missions!

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