Japan soft-landed a probe on the Moon today - a first for the nation - though its spacecraft is struggling to generate power from its solar arrays.

Launched into space on September 6, the Smart Lander for Investigating the Moon - aka SLIM aka the Moon Sniper - reached lunar orbit on Christmas Day. After circling our natural satellite for a few weeks, it finally touched down on its surface at 1520 UTC Friday. SLIM successfully made contact with its mission control, and initial checks showed its temperature and pressure were looking good. 

There is one problem: the lander is struggling to generate any electricity from its solar panels. In a press conference officials at Japan's space agency JAXA confirmed SLIM is right now operating from its batteries and only has a few hours of power left. Engineers are trying to gather as much data as possible to figure out why the panels aren't working as expected, down to the root cause.

It's possible SLIM may have landed with its solar panels covered, masked, or damaged in some way, preventing it from receiving or using sunlight and charging its batteries. In an attempt to keep the mission going, JAXA said it may turn off the batteries to reserve the probe's supplies, and switch them back on when sunlight is hitting the vehicle at a different angle. At that point, the solar panels maybe able to generate enough power to top up the batteries and allow the fault to be further diagnosed. 

"First and foremost, a landing was made and communication was established," JAXA president Hiroshi Yamakawa said. "So minimum success was made in my view. As for the details, a detailed data assessment will take place in the future." The agency will, among other things, be looking for signs that its spacecraft landed at its predicted spot, give or take 100 metres.

SLIM carried two payloads aboard: the imaginatively named Lunar Excursion Vehicle 1 (LEV-1) and Lunar Excursion Vehicle 2 (LEV-2). Both appear to have successfully separated from the lander and are being used to inspect the landing vehicle.

Even if the probe doesn't last beyond the first day, JAXA says it has successfully executed the agency's first-ever soft landing, which is arguably the most difficult part of exploring the lunar surface. Japan is now the fifth nation to achieve this feat after the Soviet Union, the US, China, and India. Japan's first attempt ended in failure when ispace, a private company headquartered in Tokyo, crashed its Hakuto-R lunar lander last year in April. 

Meanwhile, the first private, unmanned American Moon landing mission launched by Astrobotic on January 8 suffered a propellant leak as it was flying towards the natural satellite. Without enough fuel to keep it going, the privateers have sent the craft back toward Earth, where it will disintegrate in our planet's atmosphere.

The ultimate goal of the SLIM mission was to test the accuracy of its lunar landing technology, and see whether it's possible to study the Moon in detail using smaller and lighter hardware. In that regard, it hasn't completely failed.

When asked to rate the mission's success, the space agency's Office of the Director General Hitoshi Kuninaka smiled awkwardly and said "60," presumably out of 100. ®

https://www.theregister.com//2024/01/19/japan_moon_landing/