Leonard David's INSIDE OUTER SPACE

Credit: New China TV/Inside Outer Space screengrab

China’s Chang’e-5 mission remains on track for dispatching its lunar lander/ascender to descend within the northwest region of Oceanus Procellarum, also known as the Ocean of Storms. The craft is to land near Mons Rümker, a volcanic complex in the northern region of Oceanus Procellarum. 

China’s Chang’e-5 lunar mission will attempt to haul back to Earth samples of the Moon.
Credit: CNSA/CLEP

Within 48 hours, a robotic arm of the lander-ascender will be extended to scoop up rocks and regolith on the Moon’s surface and a drill will bore into the ground.

Credit: CCTV/CNSA/Inside Outer Space screengrab

“We plan to sample 15 times and collect a total of two kilograms of lunar soil,” said Liu Jiangang, chief dispatcher of Chang’e-5 mission Beijing base in a recent interview with

China Central Television (CCTV).

Ascender departs lunar surface with samples. Credit: New China TV/Inside Outer Space screengrab

“In fact, the entire stay on the lunar surface, including sampling, scientific explorations, image formation and the preparation for the take-off, is only 48 hours. The time planned for the sampling alone will be about 20 hours,” Liu said.

Orbiter and ascender rendezvous and dock above the Moon. Credit: New China TV/Inside Outer Space screengrab

Back to Earth

The ascender will depart the lunar surface with its specimens then dock with the orbiter-returner for transfer of the samples. This will be followed by the returner heading back to Earth when the geometric relationship between Earth and the Moon is suitable.

Reentry capsule heads for Earth landing.
Credit: CCTV/Inside Outer Space screengrab

The returner, with the samples on board, will then reenter the atmosphere and land at Siziwang Banner in north China’s Inner Mongolia Autonomous Region in mid-December.

Fiery reentry for capsule carrying lunar samples.
Credit: CCTV/Inside

“In the process of returning, we will make six landing forecasts at different times to grasp the returning situation in real time to ensure the smooth recovery,” said Liu.

Map of Rümker region, target of Chang’E-5 sample return mission. Credit: Y. Qian, et al.

Uncertainties

Chang’e-5’s sampling duties are full of uncertainties, according to Peng Jing, deputy chief designer of the Chang’e-5 probe from the China Academy of Space Technology (CAST) under the China Aerospace Science and Technology Corporation.

“We are not sure whether the landing site is made of hard rock or loose soil, so we have developed sampling instruments for different scenarios,” Peng said in a Xinhua news agency story. “We developed two sampling methods, including drilling underground and collecting samples from the lunar surface, to increase the chance of acquiring more diverse samples.”

Carry moonbeams home in a jar?
Onboard China’s Chang’e-5 probe used to encapsulate lunar soil samples. Source: China Aerospace Tourism

The packaging and sealing of the lunar collectibles also required an elaborate design to prevent leakage and contamination. Special care has been taken to avoid contaminating the lunar samples and limiting their scientific value.

Furthermore, the takeoff from the Moon of the ascender will also be a difficult task. Peng said the lander will act as the “launching pad” of the ascender. But the lander might not be horizontal and stable, possibly landing on a slope or complex terrain. “The spacecraft needs to conduct autonomous positioning and attitude determination during takeoff,” Peng told Xinhua.

The PolyU-developed Surface Sampling and Packing System involves two samplers for collecting samples of lunar regolith in loose and sticky form. Device shown is for collecting sticky lunar sample.
Credit: PolyU

Sampling system

China’s Chang’e-5 mission carries a Surface Sampling and Packing System developed by researchers at The Hong Kong Polytechnic University (PolyU).

The PolyU-developed Surface Sampling and Packing System can collect samples of lunar regolith in loose and sticky form. The device shown is for collecting loose lunar samples.

The packaging and sealing system designed and made by PolyU researchers is for sealing the samples in a container.
Credit: PolyU

The system includes two samplers that can withstand 200 °C for collecting samples of lunar regolith in loose and sticky form, two heat-resistant near-field cameras for vision guidance during sample acquisition, and a packaging and sealing system for sealing the samples in a container, according to a PolyU statement.

Following lunar sample acquisition, a robot arm will, through vision guidance, lift the PolyU designed and made container and place it into the Chang’e-5 ascender. The ascender then heads off into lunar orbit, docks with the orbiter and transfers the sample container to the return vehicle for its journey back to Earth. During the rendezvous and docking, there is only a five-centimeter margin of error when controlling the two spacecraft.

The PolyU Surface Sampling and Packing System team is under the leadership of Yung Kai-leung. Readying the hardware was an effort that took from 2011-2017.

Professor Yung said: “The return of samples from the Moon is technically complex. It takes more than six prototype productions through various stages of space qualification procedures in order to complete the project, not to mention the pre-production research, system design, discussions and meetings in collaboration with the China Academy of Space Technology.”

In addition to the PolyU-provided system itself, a high-precision high-resolution 3D mapping and geomorphologic capability was developed by Professor Bo Wu from PolyU’s Department of Land Surveying and Geo-Informatics. Characterization of the Chang’e-5 mission’s touchdown terrain will be vital in selecting the final landing site.

PolyU researchers have an enviable track record, also developing a “Camera Pointing System” for Chang’e-3 in 2013 and for Chang’e-4’s farside landing in 2019. In addition, they developed a Mars Camera for the now en route Tianwen-1 in 2020. The “Surface Sampling and Packing System” will be used for the Chang’e-6 mission as well.

For a newly-released overview, go to this CCTV video at:

https://youtu.be/eITH7IwH4IE

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