The legendary “moe rabbit”-Yutu 2 lunar rover woke up again. On March 18th 2020, after 14 days of extremely cold moon nights, Yutu 2 awakened itself again to “re-work”, ushering in the 16th day of the moon exploration tour. So far, Yutu 2 has survived on the back of the moon for more than 400 days, with a total mileage of 405.44 meters.
“It has been more than 400 days?” Some netizens lamented the tenacity of Yutu 2’s vitality. In fact, as early as December 2019, when Yutu-2 operated for more than 340 days on the back of the moon, it has become the world’s longest human probe working on the moon. Previously, this record was set by the world ’s first lunar rover, the Soviet Union ’s lunar rover No. 1, and maintained for nearly half a century.
People who are concerned about the lunar exploration often hear the news: “Yutu 2 woke up again”, “Chang’e 4 entered the lunch break again”, and so on. So, in the more than 400 days on the back of the moon, Chang’e-4 and Yutu-2, the two Chinese probes that have attracted much attention, have done anything but “walking”, “sleeping”, “lunching and summer vacation”?
“Move the rabbit”: look back or dance
On January 3, 2020, the NASA Lunar Exploration and Aerospace Engineering Center released a photo called “Jade Rabbit Whirling Dance”, which attracted attention. Judging from the photos, Yutu 2 “painted a circle” on the spot, and “stepped on” the 360 ° selected place on the moon.
To be more precise, this is Yutu-2’s in-situ steering detection: first drive to the predetermined detection area, and then turn one turn in turn at 8 yaw angles, under different heading angles, infrared spectrometer, neutral atom detection The instrument and other equipment “go online”-start-up detection, obstacle avoidance camera imaging, after the detection is completed, the detection data is returned to the earth.
In addition, Yutu 2 also has an exclusive “Yutu look back”-rut detection. The “Yutu Pilot” of the Beijing Aerospace Flight Control Center calculated the steering angle in advance to ensure that the infrared field of view covered the ruts of Yutu-2. According to the instructions sent from the ground, Yutu-2’s “head” turned about 180 °, and “looked back” using an infrared spectrometer to detect the lunar soil that had been turned over by the rut.
Yutu 2 is still a dedicated “rabbit”-fixed-point detection. This is the study of the influence of the change of the solar altitude angle on the reflection spectrum of a certain point on the lunar surface when Yutu-2 is in the “standing” state.
According to the scientific research personnel of the Moon Exploration and Aerospace Engineering Center of the National Space Administration, when Yutu-2 traveled to a predetermined location, it turned to the selected course, and then conducted infrared detection every two hours, and conducted infrared calibration and neutral atom detection in due course. , End the fixed-point detection work before the moon night, and find the sleeping point.
Regardless of whether it is “Jade Rabbit Whirling Dance” or “Jade Rabbit Look Back”, if summed up in one sentence, in the past year, Chang’e 4 lander carried out fixed-point detection “Jing Ruo Zizi”, and Yutu 2 lunar rover launched patrol detection , It is “Ruo Ruo Tu Hao”. Quietly, a scene of “industrious development” was played on the back of the distant moon.
The data and pictures obtained by these pioneers have been analyzed and processed by ground researchers, and transformed into scientific achievements, which has expanded the boundaries of human understanding of the moon.
The statement from the Moon Exploration and Aerospace Engineering Center of the National Space Administration is that the new coronary pneumonia epidemic will hit in 2020, but this has not caused Yutu 2 and the research team behind it to press the “pause button”: on January 3, 2020 On the first anniversary of the landing of 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 research team led by Li Chunlai, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, obtained the 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 consists of low-loss lunar soil materials A large number of stones of different sizes. This is the first time that mankind has uncovered the mystery of the underground structure on the back of the moon.
Li Chun said that from this result, “some things that humans have never seen before” can be seen: from the surface of the moon to 12 meters below the ground, the stratum is a fine-grained moon soil with a small number of stones embedded in it. The splashes of the collision craters are weathered; from 12 meters to 24 meters underground, there are a large number of stones inside, forming a gravel layer and a pile of gravel, mixed in the fine-grained moon soil; and from the underground 24 Meters to 40 meters are the deposits and weathering products of older spatters in different periods, which greatly expand the scope of human cognition.
Above the moon, the clever “Chang’e” and the hard-working “rabbit” are striving to go further, work longer hours, and provide more scientific data for humans.
A day on the moon: “sleeping” half the time
In the news about Yutu II, people often hear the words “sleep” and “wake up”, which literally understands as if it is the biological instinct of living beings, and Yutu 2 is a sophisticated lunar probe, how can it be needed? Such an operation?
This also starts with the objective environment of the moon. A day on the moon is equivalent to about 27 days on earth. Half of it is daytime, called moon day, and the other half is night, called moon night. During the moonlit night, the lunar surface temperature will drop to around minus 190 ° C. Working at too low a temperature will cause damage to the lunar rover and the scientific equipment it carries.
Therefore, before the moonlight arrived, Yutu 2 drove to the dormant point according to a predetermined strategy, turned the front of the car to the south, and the fixed side solar panel was facing east. As the sun’s altitude decreases and the temperature gradually decreases, the “Yutu Pilot” on the earth controls Yutu-2 to turn on the heating device and connect it to “heating”.
When the moon night came, Yutu 2 began to sleep, gathered the mast and one side of the solar panel, used a nuclear source for heat preservation, and entered the “dreamland” in a safe posture.
After 14 days, the sun rises, the day of the moon comes, and a new moon day begins.
When the sun shines on Yutu-2 and the fixed-side solar panel reaches a certain power generation level, it will automatically wake up and start-the power is turned on, the central computer is turned on, the active side sun wing and the mast are successively deployed, and take the initiative to “Magpie Bridge” The relay star sends a communication signal to tell the “Yutu Pilot” on the earth: “I’m up!”
After receiving the signal, the ground “Yutu Pilot” will send the latest command to Yutu 2 and set the parameters. Yutu 2 will enter the working state of the moon and day.
Of course, even in the “daytime” of the moon, this “rabbit” is not a “workaholic” plunging into scientific exploration. When the “noon” of the moon and the moon came, the temperature on the surface of the moon reached its highest level, and Yutu 2 turned its head westward. Correspondingly, the ground “Yutu Pilot” set Yutu 2 to enter the minimum working mode, so that it can better enter the “noon heat” on the noon.
As the altitude angle of the sun decreases, the temperature gradually decreases, and after falling to a suitable working temperature, the ground “Yutu Pilot” sets Yutu-2 to exit the minimum working mode and start the “afternoon” work on the moon and the day.
To live longer, adequate “sleep” and adequate “rest” are necessary. In this sense, “Moon Night Rest” and “Moon Day Lunch Break” are also part of Yutu II’s work.
“Longevity rabbit”: the detection results are more important
According to data previously released by the National Space Administration, the design life of Yutu 2 is 3 months. Today, the survival time of Yutu-2 has already exceeded this number, and even surpassed the “predecessors” of the Soviet Union, becoming the longest working longevity rabbit.
However, according to Liu Dianfu, the chief designer of Yutu 2 Mobile Subsystem of the Eighth Academy of China Aerospace Science and Technology Corporation, neither the longevity of Yutu 2 nor the distance traveled is the most important indicator at present. In his view, the more important question is whether Yutu-2 can detect more scientific achievements.
He said that 3 months is just the “lifeline bottom line” designed by scientific researchers. Under the premise of meeting the bottom line requirements, 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 finally worked on the moon for 972 days.
According to Liu Dianfu, the so-called “design life” is based on engineering goals: On January 3, 2019, the Chang’e-4 probe successfully landed at the von Carmen 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 exploration was carried out separately; on January 11, the two devices completed the mutual imaging, the scientific load of China and foreign countries worked normally, and reached the project’s established goals, marking the success of the Chang’e-4 project success.
“The completion of these engineering goals has achieved the predetermined plan, and the researchers have designed the life span of Yutu No. 2 according to these goals.” Liu Dianfu said that the subsequent detections are, to some extent, “prescribed actions” “Outside the task.
Six years ago, Yutu 2’s “sister” Yutu, 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 event of Zhang Yuhua, deputy chief commander and deputy chief designer of No. 4 Chang’e 4 of the Eighth Academy of China Aerospace Science and Technology Corporation. Enough!”
Since then, Zhang Yuhua led the team to continuously optimize the design and repeatedly evaluate and verify that they spent 5 years to ensure that the follow-up tasks are foolproof. She said: “When I saw ‘Jade Rabbit’ standing on the barren moon, I thought it was like a silver-white swan, more beautiful than anything. Now our Jade Rabbit 2 is on the back of the moon, we hope it is beautiful and brave ,Go all the way.”
Shen Zhenrong, chief designer of the Chang’e-4 inspector of China Aerospace Science and Technology Corporation No. 5 Academy, said that Yutu 2 is more “sturdy” than Yutu and has a stronger ability to cope with difficulties. “If you compare it to a child, Although the appearance does not seem to have changed much, it is more mature and the internal power is stronger. “From this perspective, the future performance of Yutu 2 is also worth looking forward to.
In the previous month and day, at the request of the team of scientists, Yutu 2 approached an impact crater on the south side of the travel route. Because the surrounding terrain was too complicated, this “rabbit” had to “look at the pit.” But in the end, it still detected the spattered gravel in front of the pit, and took a panoramic photo of the impact crater, which is also worthwhile.
Subsequently, Yutu No. 2 turned around, resolutely bid farewell to the deep pit on the south side, and continued to explore the journey. Waiting for it will be the next lunar day.