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BEIJING, June 2 (Xinhua) — China’s Chang’e-6 probe landed on the far side of the moon on Sunday morning and will collect samples from this rare area for the first time in human history, announced the China National Space Administration (CNSA).
With the support of the Queqiao-2 relay satellite, China’s Chang’e-6 probe’s landing and ascent module successfully landed in the designated landing area in the Aitken Basin in Antarctica at 06:23 Beijing time.
Chang’e-6 consists of an orbital module, a return module, a lander and an ascent module. Since its launch on May 3 this year, it has gone through multiple stages, including Earth-Moon transfer, near-moon braking, lunar orbit, and descent to the moon. The lander and lunar module separated from the orbiter and return module combination on May 30, according to the China National Space Administration.
The lunar module and ascent module combination began powered descent at 06:09. The variable thrust main engine was ignited, and the combination quickly adjusted its position and gradually approached the lunar surface.
During the descent, an autonomous visual obstacle avoidance system is used to automatically detect obstacles, and the visible light camera selects a relatively safe landing area based on the brightness conditions of the lunar surface.
The combination then hovered about 100 meters above the safe landing area and used a 3D laser scanner to detect obstacles on the lunar surface to select the final landing site, and then slowly descended vertically. When the combination approached the lunar surface, it shut down the engine and landed in free fall under the protection of the cushioning system.
The Chang’e-6 mission is tasked with collecting and returning samples from the far side of the moon, the first such effort in human lunar exploration history.
The project has made breakthroughs in retrograde lunar orbit design and control technology, aiming to form key technologies for BroadCast Unitedligent rapid sampling and takeoff and ascent from the far side of the moon.
The landing site is an impact crater known as the Apollo Basin, located within the Aitken Basin in the South Pole. Huang Hao, a space expert at the Chinese company Aerospace Science and Technology (CASC), said the choice was made because of the potential value of the Apollo Basin in scientific exploration, as well as the conditions of the landing area, including communication and telemetry conditions and the flatness of the terrain.
Huang added that the terrain on the far side of the moon is steeper than that on the near side, with fewer continuously flat areas. However, the Apollo Basin is relatively flatter than other areas on the far side, making it suitable for lunar landing.
The lander is equipped with a variety of sensors, including microwave, laser and optical imaging sensors, which can measure distance and speed and identify obstacles on the lunar surface, Huang said.
In order to prevent lunar dust from interfering with the optical sensor during landing, the lander is also equipped with a gamma-ray sensor that uses a particle beam to accurately measure the altitude, ensuring that the engine can be shut down in time and the lunar module can land smoothly on the lunar surface, Huang added.
At the same time, the landing legs act as shock absorbers, absorbing the landing impact energy and ensuring the safety of the equipment on the lander.
After landing, the probe plans to complete sampling within two days. It uses two methods to collect lunar samples, one is to use a drill to collect samples from underground, and the other is to use a robotic arm to collect samples from the surface.
Another aerospace expert, Jin Shengyi, introduced that the Chang’e-6 probe development team had previously built a simulation laboratory to ensure the smooth progress of the sampling process.
Team members will build a full-scale replica of the sampling area based on the Chang’e-6 exploration results, the environment around the landing site, rock distribution, and lunar soil conditions. They will use simulations to develop and verify sampling strategies and equipment control procedures to ensure the accuracy of instructions.
Due to the obstruction of the moon itself, even with the help of the Queqiao-2 relay satellite service, the Earth-Moon communication window period with the far side of the moon is shorter than that with the near side. Therefore, the sampling time of Chang’e 6 will be shortened to about 14 hours, while the sampling time of its predecessor Chang’e 5 was 22 hours.
Jin explained that in order to save time and improve efficiency, the development team made the sampling process smarter, allowing Chang’e-6 to autonomously execute instructions and make decisions to reduce interactions between the Earth and the Moon.
For example, after the ground control sends a command, the probe will execute the corresponding program multiple times, and then use the real-time data collected by the sensor to evaluate whether the command is executed well, thereby achieving closed-loop autonomous work without any operation. The ground control must send a command for each action.
Nearly a thousand commands were sent from Earth during the Chang’e-5 sampling process. For Chang’e-6, this number is expected to drop to around 400.
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