Unraveling Chang'e-6: How do China's researchers operate its lunar 'excavator' 380,000 km away?

China's historic lunar sampling mission Chang'e-6 is nearly halfway through, with the ascender entering the lunar orbit on June 4. But before that, the sampling process was a carefully choreographed ballet of science and engineering.

China obtained samples from the near side of the moon during the Chang'e-5 mission in 2020. However, working on the far side of the moon, which is completely invisible from Earth, was particularly tricky. 

According to Jin Shengyi with the China Aerospace Science and Technology Corporation, who knows the process well, the first step was to have exact replicas of the probe's working area, some 380,000 kilometers away. 

Researchers at the ground laboratory used data from the Queqiao-2 relay satellite to simulate a geographic model of the sampling area and the sampling process, providing important support for Chang'e-6 sampling decisions.

Jin and his team on the ground would first analyze the data of the perceptual imaging of the landing location obtained by Chang'e-6 and then build a digital model of the location. After that, they built a physical replica based on the digital model that resembles the lunar surface environment 1:1.

"We place a sample-gathering mechanism in this replica environment, which is also tuned to the same status as the one on the moon," Jin said. "In this reconstructed physical environment, we select sampling points and establish sampling strategies and also verify them in this reconstructed environment."

The team selected more than 10 sampling points and ordered the robotic arm to work on them in just one request, thanks to the intelligent sampling system. The probe also collected lunar samples through drilling, which took three hours.