The Chang'e 4 mission is the third lunar day. Rover "Yutu-2" in search of ... stones

Yutu-2 lunar rover drove 43 meters in the third lunar day, adding them to the 44 (44.185) meters passed on the first lunar day and 76 meters (75.815) on the second lunar day. Total covered 163 meters in three lunar days. Is it a lot or a little? And why is such a short distance the lunar rover travels in this mission?


The third lunar day for the Chang'e-4 mission is the period from February 27, 2019 to March 13, 2019:





Currently, from March 13, 2019, the equipment of the Chang'e-4 landing module and the Yutu-2 rover have been put to sleep mode before the end of the third moonlit night to survive a period of extremely low-temperature environment on the far side of the moon.

What is the surface on the far side of the moon?



Since the reverse side of the Moon also has a more complex relief than the side visible from the Earth, in the process of moving along the surface, the Yutu-2 rover encountered more serious motor problems and interference, compared with those that its rover predecessor had previously encountered " Yutu, "sent to the lunar surface in 2013.

Unfortunately, the first Yutu rover of the Chang'e-3 mission, on January 25, 2014, was technically immobilized (damage to elements as a result of a collision) after overcoming 114.8 meters on a complex lunar surface.

The lunar surface in the landing zone of the Chang'e-4 landing module is replete with folds, numerous pebbles and small craters, after making each of its small movements, the Yutu-2 rover should stop, photograph the surface around and send this data back to Earth via satellite repeater.



Scientists, operators at the MCC and engineers on Earth then process this data and chart a further route along which the Yutu-2 rover will follow.

Yutu-2 rover antennas must be configured so that they point to a repeater satellite to correctly send and receive control signals, while rover solar panels should be optimally tilted to receive a lot of sunlight to maximize output electricity at the time of the data transfer.



Six-wheeled rover "Yutu-2":

- the total mass of the rover is about 140 kg (310 pounds);
- carrying capacity - about 20 kg (44 lbs);
- can move along slopes and has automatic sensors that prevent collision with other objects;
- the rover is provided with electricity using two solar panels, allowing the rover to work during a lunar day;
- the maximum speed of 200 meters per hour (this speed on the Moon can still not be reached - since the elements on the surface will not allow to accelerate and disable the rover earlier);
- maximum research area - 3 square meters. km;
- Estimated working time - 3 months (2160 hours);
- The maximum estimated distance is 10 km.



At the moment, 70 days (1680 hours) have passed since the Yutu-2 rover landed on the Lunar surface and 97 days (2328 hours) after the Yutu-2 rover launched from the Sichan cosmodrome as part of the Chang'e-4 mission to the Moon.

In fact, the Yutu-2 rover has already worked out its estimated working life, but in case of a successful “wake-up” after sleep on March 27, 2019, it is planned that it will continue to conduct surface research on its fourth lunar day.

But how much its capabilities in terms of working capacity is enough is already beyond the design norm and problems or breakdowns in components and systems will begin, as large temperature drops, radiation, pollution and other lunar external factors will affect its characteristics more strongly every hour.

The trajectory of the movement of the Yutu-2 rover on the first lunar day and part of the second lunar day:



You can check the photo of the landing site that the NASA LRO probe took from a height of 82 kilometers, a resolution of 0.85 meters (33 inches) per 1 pixel:



At this moment, the Yutu-2 rover is located at a distance of more than 80 meters diagonally from the Chang'e-4 landing module and has traveled 163 meters after its landing.



Why did the Yutu-2 rover drive so little?

Firstly, it is a “fear” of immobilizing the Yuta-2 rover (and not repeating the fate of the first Yuta rover), therefore, the Yuta-2 rover must move around the surface of the Moon, carefully avoiding obstacles. Each centimeter of his movement must be done carefully and correctly. In the MCC of the Chang'e-4 mission, they try to avoid a situation in which the Yutu-2 rover rolls over, which means that it will not be able to return to its working position again. The solar panels on the sides of the Yutu-2 lunar rover are very fragile, they can crack or become dusty after falling, which will render them unusable.

Secondly, the far side of the Moon is more likely to fall in meteorites, therefore the terrain there is very complicated, on the Lunar surface in the landing zone there are a lot of small craters and indentations that need to be circled as far as possible, but still need to move on in search of the ones you need to study surface elements - large stones and formations. And their search and research of different formations are also necessary forced stops to conduct research in one place with a long stop time.



Thus, on the first and second lunar day, using the data from the on-board cameras of the Yutu-2 rover, a detailed map of the landing site area and the possible further route of the rover was also finalized, which turned out to be much more winding than the previously planned direct route.

On the third lunar day, the Yutu-2 rover reached a place with interesting formations on the lunar surface — sharp peaks on the surface, medium and large detached stones.

Landscape elements on the back of the lunar surface may be older than those on the visible side, so studying the soil and stones on the back can shed more light on the origin and evolution of the moon.

Who controls the Yutu-2 rover?

Telemetry, data from cameras and scientific equipment, control teams and around-the-clock monitoring of the parameters of the Yutu-2 rover are the prerogative of the engineers of the aerospace control center of the Chinese Academy of Space Technology.

In China, the moon is traditionally associated with women, the Chinese moon exploration program is also named after the moon goddess Chang'e, which emphasizes the contribution of female scientists and engineers to the development of space research.

In a Chinese legend, a girl named Changye flew to the moon and became a goddess there, but she cannot return to Earth to reunite with her husband.

The girls-engineers of the aerospace control center of the Chinese Academy of Space Technology are more fortunate - many of them have the opportunity to fly "virtually" to the moon and be simultaneously on Earth with their loved ones.

It turns out that women from the engineering team for the management and control of the Yutu-2 rover have a stronger sense of responsibility and perseverance than many of their male colleagues, they are more demanding and observant to the smallest details in the process of working with the Yutu-2 rover . Therefore, among the group of engineer-operators of the rover "Yutu-2", they can show the maximum scientific and engineering talents in their work.

Verification of telemetry data with a colleague:



Workplace of the operator of the rover "Yutu-2":



And now back to the rover "Yutu-2".

More than three billion years ago, the back of the moon was bombarded by large asteroids and meteorites, which caused a global change on its surface, traces of this process are being studied by the Yutu-2 rover.

The on-board cameras of the Yutu-2 rover are stationary, to obtain the necessary images, it is necessary to perform precise movement and adjustment of the horizontal position, as well as compensation of the tilt angle of the rover itself, which takes a lot of time for operators at the MCC. After all, the surface in the landing zone of the Yutu-2 rover is littered with craters of different sizes, which makes it very difficult to move safely.

It turns out that the Yutu-2 rover is able to automatically bypass some obstacles, if there is a large stone or crater in front of it, it can stop on its own and plan a new route to bypass this place, in this case the operator in the MCC can register this situation and rebuild the planned route to a new one.

The Yutu-2 rover can also climb small slopes and cross a rocky surface. But the main front of his work is movement on a flat horizontal surface and lunar soil.

So what kind of device is this “VNIS spectrometer” installed on board the Yutu-2 rover?

The VNIS lunar infrared spectrometer (The Visible and Near-Infrared Imaging Spectrometer) was developed at the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences.

The spectrometer uses noncollinear acousto-optic tunable filters, it consists of a VIS / NIR video spectrometer (0.45–0.95 μm) and a short-wave infrared spectrometer (0.9–2.4 μm), and it also includes a calibration unit with protection from dust and pollution.

The spectrometer is installed in front on board the Yutu-2 rover, has the following restrictions on positioning and working with lunar material:



Minerals, such as pyroxene, plagioclase, olivine and ilmenite, which make up most of the lunar surface rocks, have distinctive spectral characteristics:



Structural diagram operation of the spectrometer:



Main technical characteristics of the spectrometer:



Appearance of the spectrometer:



Geometric dimensions of the detection window:



Data obtained by the spectrometer:



On the third lunar day, the Yutu-2 rover was engaged in obtaining scientific data using the VNIS onboard stationary spectrometer (Visible and Near-Infrared Imaging Spectrometer), whose sensor field of view is only a few centimeters wide, so the rover must be very accurately and accurately positioned " Yut-2 ”so that the spectrometer's“ eye ”can be brought out to the desired area of ​​the lunar surface to receive the correct data from the optimal distance.

After a short walk on the moon, the Yut-2 rover reached an interesting stone glade, in the center of which a large stone with a diameter of 20 centimeters was discovered. Scientists were immediately interested in this find, its origin (meteorite, lunar formation) and the process of education.

General view of the surface panorama during the search for stones:



The rocky surface, to a large rock (its diameter is 20 centimeters) is a distance of 120 centimeters:



An enlarged image of a large rock:





Work with a spectrometer:





Further, data with a Yutu-2 rover spectrometer are transmitted to the aerospace control center of the Chinese Academy of Space Technologies, where they are analyzed, stored and will be open to the scientific community.

The Chinese portal “System for publishing and collecting scientific data and research of the lunar and deep space”, on which the received data and images from Chang'e-4 (and earlier missions) will be published, also worked.
Path to the portal :
http://202.106.152.98:8081/moondata/

The data volume is also an interesting point, for example, the Yut-2 rover, after taking measurements using a spectrometer at four different points on the lunar surface, transmitted a total data volume of 350 MB.

Scientific measurements of the elements of the lunar surface and data transmission from the rover "Yutu-2" are planned to continue on the fourth lunar day.