The legendary “Meng Rabbit”-Yutu 2 lunar rover awoke again. On March 18, after 14 days of extremely cold moonlight, Yutu No. 2 awakened on its own initiative and “returned to work” again, welcoming the 16th day of the moon exploration journey. So far, Yutu-2 has survived for more than 400 days on the back of the moon, with a cumulative mileage of 405.44 meters.

“It’s been over 400 days?” Some netizens expressed their stubbornness in the vitality of Yutu No.2 when they praised it. As a matter of fact, as early as December 2019, when Yutu 2 had been operating for more than 340 days on the back of the moon, it has become the world’s longest human detector working on the moon. Previously, this record was set by the world’s first lunar rover, Soviet Lunar Rover 1, and it has been maintained for nearly half a century.

  People who follow the lunar exploration often hear the news: “Yutu 2 wakes up again”, “Chang’e 4 enters lunch break again”, and so on. Then, in the more than 400 days on the back of the moon, what are the two closely-watched Chinese probes, Chang’e 4 and Yutu 2, doing nothing but “walking”, “sleeping” and “lunch break and summer heat”?

  “Moving off the rabbit”: or look back or dance

On January 3, 2020, the NASA Lunar Exploration and Space Engineering Center released a photo called “Yutu Rondo Dance”, which aroused attention. Judging from the photos, Yutu No. 2 “drawn a circle” in situ, and performed a “step on point” of 360 ° on the selected place on the moon.

More precisely, this is the in-situ steering detection of Yutu II: first travel to a predetermined detection area, and then rotate in turn at 8 yaw angles. Under different heading angles, the infrared spectrometer and neutral atom detection Devices and other equipment “online”-start detection, obstacle avoidance camera imaging, after detection, the detection data is transmitted back to earth.

In addition, Yutu No. 2 has its own “Yutu Looking Back”-rut detection. The “Yutu Pilot” of Beijing Aerospace Flight Control Center calculated the steering angle in advance to ensure that the infrared field of view covered the rut of Yutu II. According to the instructions sent from the ground, the “head” of Yutu No. 2 turned about 180 °, and the infrared spectrometer “looked back” to detect the lunar soil that was rolled out by the rut.

Yutu No. 2 is also a dedicated “rabbit”-fixed-point detection. This is the study of the influence of the change of the sun’s height angle on the reflection spectrum of a certain point of the moon in the “standing” state of Yutu-2.

According to researchers from NASA ’s Lunar Exploration and Space Engineering Center, when Yutu-2 traveled to a predetermined location, it turned to the selected course, and then carried out infrared detection every two hours, performing infrared calibration and neutral atom detection in a timely manner. , End the fixed-point detection work before the dawn of the moon, and find the dormant point.

Regardless of whether it is “Yutu Rondo” or “Yutu Looking Back”, if it is summarized in one sentence, in the past year or more, Chang’e 4 lander has carried out fixed-point detection, “Just a Virgin”, and Yutu 2 lunar rover has conducted patrol detection , It is “moving away from the rabbit.” With one motion and one motion, a “diligent and pioneering” landscape is staged on the far side of the moon.

The data and pictures obtained from these pioneering works have been analyzed and processed by ground-level scientific researchers and transformed into scientific results, which has expanded the human understanding of the moon.

The statement from the NASA Lunar Exploration and Aerospace Engineering Center is that the new crown pneumonia epidemic will hit in 2020, but this did not let Yutu 2 and the research team behind it press the “pause button”: on January 3, 2020 On the first anniversary of the landing of Sun Chang’e-4 on the back of the moon, the center released more than 210GB of scientific data at various levels, and a team of Chinese and foreign scientists made a series of important scientific discoveries based on these data.

On February 27, a scientific research team led by Li Chunlai, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, obtained in-situ detection data through the lunar radar mounted on Yutu-2. After research, it was found that the underground material on the back of the moon is composed of low-loss lunar soil matter and Made up of a large number of stones of different sizes. This is the first time that humans have unveiled the mystery of the underground structure on the back of the moon.

For Li Chun, from this achievement, we can see “some things that humans have never seen before”: from the surface of the moon to 12 meters below the ground, the layer is a fine-grained lunar soil with a small number of stones embedded in it. The spatters of the impact craters are weathered; from 12 meters to 24 meters underground, there are a large number of stones inside, forming a gravel layer and gravel piles, which are contained in fine-grained lunar soil; Meters to 40 meters are the products of different periods and older sputter deposits and weathering, which have greatly expanded the scope of human cognition.

Above the moon, the wise “Chang’e” and the hard-working “rabbit” are working hard to go further, work longer, and provide more scientific data for human beings.

A day on the moon: “sleeping” half the time

In the news about Yutu II, people often hear the words “dormant” and “wake”, and literally understand the biological instincts of life. Yutu II is a precise lunar probe, so how do you need it? Such an operation?

This also starts from the objective environment of the moon. A day on the moon is equivalent to about 27 days on the earth, half of which is daytime, called moon day, and the other half is night, so-called moon night. During the moonlight night, the lunar surface temperature will drop to minus 190 ° C. Working at excessively low temperatures will cause damage to the lunar rover and its scientific equipment.

Therefore, before the moonlight arrived, Yutu No. 2 drove to the dormant point according to the predetermined strategy, turned the front of the car to the south, and the fixed-side solar sail faced east. As the altitude angle of the sun decreases and the temperature gradually decreases, the “yutu driver” on the earth controls Yutu 2 to open a heating device and connect to “heating”.

When the moonlight came, Yutu No. 2 began to dormant, set up the mast and one side of the windsurfing board, use nuclear source to keep warm, and use a safe posture to enter “dreamland”.

Fourteen days later, the sun rose, the day of the moon came, and a new moon day began.

When the sun shines on Yutu No.2, the fixed-side solar windsurfing board reaches a certain power generation level, and it will automatically wake up and start-the power is turned on, the central computer is turned on, the active-side solar wing and the mast are sequentially deployed, and they actively take the “Bridge Bridge” The relay star sent a communication signal to tell the “Jade Rabbit Driver” on the earth: “I got up!”

After receiving the signal, the “Yutu driver” on the ground sends the latest instructions to Yutu No. 2 to set the parameters, and Yutu No. 2 enters the working mode of day and month.

Of course, even in the “day” of the moon, this “rabbit” is not a “workaholic” plunging into scientific exploration. When the “noon” of the day came, the temperature on the surface of the moon reached the highest, and Yutu No. 2 turned its head west. Correspondingly, the “Yutu driver” on the ground set the Yutu No. 2 to enter the minimum working mode, so that it can better enter the “no summer heat” at noon.

As the altitude angle of the sun decreases, the temperature gradually decreases, and after the temperature reaches a suitable working temperature, the “Yutu driver” on the ground sets the Yutu 2 to exit the minimum working mode and start the work in the “morning” of the moon and day.

In order to live longer, sufficient “sleep” and “rest” are necessary. In this sense, “Moon Night Break” and “Month Day Lunch Break” are all part of the work of Yutu II.

“Long-lived rabbit”: detection results are more important

According to data previously released by NASA, the design life of Yutu-2 is 3 months. Today, the survival time of Yutu II has already exceeded this number, even surpassing the “predecessors” of the Soviet Union, becoming the “longevity rabbit” with the longest working hours.

However, in the view of Liu Dianfu, chief designer of the mobile sub-system of Yutu No. 2 of the Eighth Academy of China Aerospace Science and Technology Corporation, neither the length of Yutu No. 2’s life nor the distance of its walking distance are currently the most important indicators. In his view, the more important question is whether Yutu II can detect more scientific results.

He said that 3 months is just the “bottom line of life” designed by scientific researchers. Under the premise of meeting the requirements of the bottom line, the scientific research team certainly hopes that Yutu 2 can work for one year or more. In fact, the design life of China ’s first lunar rover Yutu was only 3 months, but it eventually worked on the moon for 972 days.

According to Liu Dianfu, the so-called “design life” is based on the engineering goals: on January 3, 2019, the Chang’e-4 probe successfully landed on the von Carmen impact crater in the Antarctic-Aitken Basin on the back of the moon; January On the 4th, the Yutu 2 lunar rover was successfully separated from the lander, and scientific detection was carried out respectively. On January 11, the two vehicles completed mutual imaging, and the Chinese and foreign scientific payloads were working normally, reaching the project’s stated goals, marking the successful completion of the Chang’e 4 project mission. success.

“The completion of these engineering goals has achieved the planned plan. Scientific researchers have designed the lifespan of Yutu No. 2 based on these goals.” Liu Dianfu said that the next detection, to a certain extent, was “prescribed actions.” “.

Six years ago, Yutu No. 2’s “sister” Yutu No.2, after walking 114.8 meters on the moon’s Rainbow Bay, suddenly had a cable short circuit and could no longer walk. This was the most memorable thing of Zhang Yuhua, deputy chief commander and deputy chief designer of Chang’e 4 of the Eighth Academy of China Aerospace Science and Technology Group. “I thought at the time, if you could send me to the moon and bandage it, it might be a ‘Jade Rabbit’. Enough!”

Since then, Zhang Yuhua led the team to continuously optimize the design and repeatedly evaluate and verify. They spent 5 years to ensure that the follow-up tasks are foolproof. She said: “When I saw the ‘Jade Rabbit’ standing on the barren moon, I felt it was like a silver swan, which is more beautiful than anything. Now our Jade Rabbit 2 goes to the back of the moon, and we hope it is beautiful and brave. ,Go all the way.”

Shen Zhenrong, the chief designer of the Chang’e-4 inspector of the Fifth Academy of China Aerospace Science and Technology Group, said that compared with the Yutu, Yutu-2 is more “sturdy” and more capable of coping with difficulties. “If it is likened to a child, Although the appearance does not seem to have changed much, it is more mature and the internal strength is stronger. “From this perspective, the future performance of Yutu II is also more worth looking forward to.

On the previous day of the month, at the request of the scientist team, Yutu No. 2 approached an impact crater on the south side of the route. Because the surrounding terrain was too complicated, the “rabbit” had to “sigh with regret”. But in the end, it still detected the spattered gravel in front of the pit, and took a panoramic photo of the impact pit, which is not a bad trip.

Subsequently, Yutu No. 2 turned around and resolutely bid farewell to the deep pit on the south side and continued to explore. Waiting for it will be the next lunar day.

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