Japan Moon Lander Sleeps After Sending Science — Will It Wake Up Again?

After a few days of wakefulness, Japan’s SLIM moon lander has gone dormant once more at the start of a 14-day-long lunar night. The upended robot sent back a stream of data and imagery while its solar cells were in position to soak up sunlight, and its handlers hope they can get SLIM to wake up again and resume its work after lunar sunrise in mid-February.

The car-sized robot accomplished its primary mission on Jan. 20 (Japan time) when it landed within 100 meters of its target point near Shioli Crater. SLIM — which is an acronym standing for “Smart Lander for Investigating Moon” — was designed to demonstrate a precision landing technique that Japan hopes to use for future missions to the moon and Mars.

Unfortunately, the lander ended up in an upside-down position, with its solar cells pointing off to the side. Mission managers were able to get some data and pictures back — including a photo captured by a mini-robot that documented the lander’s predicament. But within hours, the lander’s batteries ran down to the point that SLIM had to go into hibernation. The mission team could only hope that as the sun moved westward in the lunar sky, enough light would eventually hit the panels to allow for a reawakening.

That’s exactly what happened on Jan. 28: The Japan Aerospace Exploration Agency, a.k.a. JAXA, re-established contact with the charged-up SLIM and commanded the lander to transmit a set of multispectral images showing the area around the landing site — including a variety of rocks named after canine breeds, such as Bulldog, Toy Poodle and Aki Inu.

SLIM’s recent science-gathering session was limited to just a few days due to the moon’s day-night cycle. By the time the lander’s solar cells soaked up enough sunlight, it was the equivalent of late afternoon on the moon. Sunset came on Feb. 1, and once again, SLIM went into hibernation.

“We sent a command to switch on SLIM’s communicator again just in case, but with no response, we confirmed SLIM had entered a dormant state,” the mission team at the Japan Aerospace Exploration Agency said in a posting on X / Twitter.

The final image sent back by the lander shows a dark stretch in the foreground, with the sun’s dying rays reflecting off rocks and off the heights of a ridge rising in the background.

Temperatures were expected to fall to somewhere around 200 degrees below zero Fahrenheit (-130 degrees Celsius) during the lunar night. JAXA initially had planned to let the lander go dead when the sun went down — but in light of the unlucky lander’s recent resilience, those plans could change.

“Although SLIM was not designed for the harsh lunar nights, we plan to try to operate again from mid-February, when the sun will shine again on SLIM’s solar cells,” mission managers said.