SLIM · the upside-down lander

SLIM, the Smart Lander for Investigating Moon, is a small Japanese lander built by JAXA, Japan's space agency. Its nickname was the Moon Sniper, because its goal was a pinpoint landing within 100 m of a chosen spot. On 19 January 2024 it came down near Shioli, a small crater close to the Sea of Nectar, and Japan became the fifth country to make a soft landing on the Moon.

The landing did not go quite to plan. Shortly before touchdown one of its two main engines failed, and SLIM ended up resting on its nose, almost upside down. Even so, it landed about 55 m from its target, so the precision goal was met. A tiny ball-shaped robot it carried, SORA-Q, took the first picture of the tipped-over lander.

The mission

SLIM launched on 6 September 2023 on an H-IIA rocket from Tanegashima, sharing the ride with an X-ray space telescope. Most landers aim for a wide, safe area several kilometres across. SLIM instead used a camera to compare the ground below with maps and steer itself toward an exact point. Engineers hope this kind of pinpoint landing will let future missions set down right next to the rocks and craters scientists most want to study.

The upside-down lander

At about 50 m above the surface, SLIM lost one engine. Its software kept control, but it was moving sideways and tilted too much, so it settled on its nose. Its solar panels then faced west, away from the morning Sun, and the team switched it off to save the battery. About nine days later, sunlight reached the panels and SLIM woke up. It was not built to survive the freezing lunar night, but it still woke up after several of them before going silent in 2024.

The tiny robot photographer

Just before landing, SLIM dropped two little rovers. LEV-1 hopped across the ground and sent data straight to Earth. LEV-2, also called SORA-Q, is about the size of a baseball and weighs about 250 g. It was made by JAXA together with the toy company Tomy, Sony and Doshisha University. It splits open into a shape with two wheels to roll along, and it photographed SLIM resting on its nose.

On the 3D Moon

On the 3D Moon you can see SLIM near Shioli crater, standing on its nose after its engine trouble, with the little ball robot SORA-Q nearby.