Highlighting work of Shanghai scientists in Chang'e-5 mission

Ti Gong

Ti Gong

The world is now awaiting the return of the first lunar samples in 44 years. In China’s first sample-return attempt, local researchers are putting their shoulders to the wheel.

Traveling 380,000 kilometers in seven days, China’s sixth lunar mission Chang'e-5 landed on the Oceanus Procellarum, or “Ocean of Storms,” a previously unvisited area in a massive lava plain on the near side of the moon, on December 1.

After a 19-hour operation, it finished collecting, packaging and sealing samples of lunar soil and rock. A spacecraft carrying the samples lifted off from the lunar surface on December 3, and is scheduled to return home in mid-late December.

If successful, China will also be the third nation to bring lunar samples to the Earth after the United States and the former Soviet Union. Also, it will be the first to bring lunar samples to the Earth in 44 years after the former Soviet Union’s Luna 24 mission in 1976.

The spectrometer developed by the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences has scanned all  the sampling area, providing useful scientific data for research in lunar science.

It works based on sunlight reflected on the moon. It can tell the distribution of minerals in the sampling area and reveal the mineral composition of samples, according to He Zhiping, a researcher from the institute.

“No man has ever walked on the sampling area," he said. "It’s a virgin land showing the moon in the raw. So, before and after sampling, mineral composition of lunar soil on the surface and sub-surface may show some differences, the spectral data may help us understand evolution of the moon."

Compared with predecessors onboard Chang’e-3 and Chang’e-4, the newest generation is equipped with an extended wavelength range, which enables it to detect hydroxyl in hydrates. 

“It probably provides useful reference to find traces of water and hydroxyl on the moon,” He said. 

Also, it can rotate automatically to detect what it wants to detect in a certain range.

The other state-of-the-art payloads developed by the institute work as “obstacle avoidance laser radars” to ensure the soft landing of the probe, according to Shu Rong, deputy director of the institute.

Chang’e-5 has successfully avoided hitting rocks and craters on the moon surface by shifting parallell 6 meters, and made a stable and soft landing.

When it was about 20 kilometers above the moon, the laser range sensor began its work, mapping the height to the moon’s surface. When it was 2.5 kilometers above, the laser speed sensor started to measure the descending speed of the lander. When it was only 100 meters above, a 3D imaging sensor provided 3D pictures of the landing area, according to Xu Weiming, a researcher from the institute.

“This time, we’ve cut 30 percent of the weight of other payloads to make room for the laser speed sensor," he said. "It’s an emerging technology that can detect very slight speed change, even 0.1 meter per second."

Other Shanghai institutes under CAS have also made their contributions to the probe.

The Shanghai Astronomical Observatory of the CAS is using the Very Long Baseline Interferometry to track and position Chang’e-5 on its 23-day journey.

China’s VLBI system is made up of a VLBI center and four stations in Shanghai, Beijing, Kunming in southwest Yunnan Province and Urumqi in the northwest Xinjiang Uygur Autonomous Region. They form one giant “telescope” with a diameter of more than 3,000 kilometers.

The system allows researchers on the Earth to have immediate access to Chang’e-5’s exact position.

The journey to the moon is tough. Spacecraft are exposed to an extremely tough environment where temperatures can quickly swing from 100 degrees Celsius above zero to 100 degrees below zero.

So, the Shanghai Institute of Organic Chemistry of the CAS has designed thermal control coatings for the spacecraft. The coatings featuring different levels of solar absorption and thermal emittance.