Waiting for the Sun: Solar Cells Face the Wrong Direction, Japanese Slim Lander ‘Put to Sleep’ on the Moon – Sunshine From the West May Salvage Mission

 

The Moon is experiencing a rush of visitors, with many countries sending multiple missions in space missions where, sometimes, success and failure can be found locked in a cosmic embrace, waiting for the Sun.

Take the Japanese Lunar lander SLIM, the ‘moon sniper’ with a technology that allowed it, four months after lifting off from the Japanese Tanegashima Space Centre, to touch down closer to its target landing site than any mission has before – a less than 300 feet radius.

A resounding success that put Japan in the exclusive Lunar Space club with the Soviet Union, the US, China and India.

But not everything went according to plan in SLIM’s arrival. He might have rolled during upon landing, or something else happened, preventing its solar cells from facing the Sun to the east as they were supposed to. 

With batteries rapidly draining and solar cells facing west, the spacecraft was ‘put to sleep’ just three hours after its historic lunar touchdown.

That result would mean a partial failure of the mission – but the Japanese space agency thinks it can still salvage it if sunlight just hits it in the right place.

BBC reported:

“‘If sunlight hits the Moon from the west in the future, we believe there’s a possibility of power generation, and we’re currently preparing for restoration’, the Jaxa statement read.

[…] The battery was disconnected according to our procedures with 12% power remaining, in order to avoid a situation where the restart (of the lander) would be hampered’, Jaxa said.”

Before shutdown, mission control gathered technical data from the spacecraft and images from its descent to the lunar surface.

“Moon missions try to land early in the ‘lunar day’, when the Sun comes up over the eastern horizon. This gives a spacecraft about two ‘Earth weeks’ of illumination before the Sun then sets in the west for two weeks of darkness.

It’s currently ‘morning’ at Slim’s landing location on the slopes of Shioli Crater. If, as suspected, the spacecraft’s solar cells are pointing westward, then it may have to wait until the ‘lunar afternoon’ before those cells catch enough light to start charging the battery system.”

SLIM was the second Moon landing attempt in 2024, after the failed US Peregrine spacecraft.

In late February, US company Intuitive Machines will try to become the first commercial company to land a spacecraft on the Moon.