China's next moon mission is nearly ready to fly

China’s next lunar landing is coming together on the ground. On 13 July, the Long March 5 rocket assigned to the Chang’e-7 mission arrived at the Wenchang spaceport on Hainan, joining the spacecraft itself, which had been trucked and flown to the island in April. With the launch set for later this year, the pieces of the mission are now being stacked and tested in the hangars, and the flight, when it comes, will be the most ambitious lunar landing China has attempted, in a category of its own even by the standards of the Chang’e series.

The mission’s target is the lunar south pole, and its objective is the region’s defining mystery: water. The pole is where the Moon keeps its shadowed craters, places where the Sun never rises above the rim and where temperatures stay cold enough to preserve ice, possibly for billions of years. No spacecraft has ever explored one of these permanently shadowed craters from the surface. Chang’e-7 is designed to be the first, and its plan of attack is built around mobility: the mission uses a combined orbiter, lander, rover and a flying probe, a small hopping vehicle that can leave the lander, fly over the crater wall and descend into the darkness to touch the ice directly.

The engineering is where the mission shows its character. Landing on the south pole means landing on terrain unlike the mare plains where previous missions set down, with steep slopes, boulders and lighting that changes only slightly over the lunar day. The lander has to touch down precisely, the rover has to survive the cold, and the hopper has to navigate and land without the sunlight that every previous lander has relied on for power and navigation. The mission also carries instruments for resource surveys and environment monitoring, and it will test key technologies that the crewed programme will need, including the ability to operate in the poles’ extreme conditions.

The date being watched is not just for the launch. Chang’e-7 is the lead mission in a sequence: Chang’e-8, expected in the next few years, will test in-situ resource use and the building blocks of a research station, and the two are designed as a pair that lays the groundwork for a permanent lunar base in the 2030s. The south pole is the chosen location for that base, partly for its water and partly for its near-constant sunlight on the crater rims, so every success and failure at the pole this decade is practice for the larger structure to come.

The international angle is present but quieter than in some earlier missions. Chang’e-7 carries international payloads and is being described in the context of China’s plans for a shared lunar research station, with several countries already signed on to future elements. The mission itself, though, is a domestic engineering achievement, and its success or failure will be judged at home first. The programme has landed on the Moon four times in this decade without a failure, and the expectation, fairly or not, is that the streak continues.

What the flight represents is the difference between visiting the Moon and living on it. The previous Chang’e missions proved that China can reach, land on and sample the near side and the far side of the Moon. Chang’e-7 is the first one built around the question of how to operate where the conditions are hostile in a new way, and how to extract what a future base would need. A successful hop into a shadowed crater would be the first time any nation has touched a piece of the Moon that has never seen the Sun, and that, more than the landing itself, is the milestone to watch when the Long March 5 lifts off later this year.