Japan became the fifth country to land a spacecraft on the moon, after the US, the Soviet Union, China and India, when its Smart Lander for Investigating Moon (SLIM) probe touched down near the Shioli crater on January 15, 2024. The mission aimed to demonstrate a new technology for precise lunar landing, which could enable future exploration of potential resources and habitats on the moon. However, the probe encountered some difficulties after landing, as its solar cells failed to generate power and it relied on its batteries for survival.
A historic pinpoint landing
The SLIM probe, nicknamed the “moon sniper”, was launched by Japan’s space agency JAXA on December 2, 2023, from the Tanegashima Space Center. It reached lunar orbit on December 23 and began to adjust its trajectory for landing. The probe was designed to land within 100 meters of a location near the Shioli crater, on the near side of the moon, where volcanic rocks are abundant. This would be an unprecedented feat of accuracy, as previous lunar landers had aimed for much wider landing zones measuring up to 10 kilometers in width.
According to JAXA, the SLIM probe successfully achieved its pinpoint landing goal, landing only 55 meters away from its target site. The probe used a combination of sensors, cameras and artificial intelligence to autonomously navigate and avoid obstacles during its descent. The landing was also broadcast live by JAXA, showing the probe’s view of the lunar surface as it approached its destination.
A close call on the lunar surface
However, the joy of landing was soon overshadowed by technical problems. JAXA officials noticed that the probe’s solar cells were not working properly and were unable to generate electricity. This meant that the probe had to rely on its batteries for power, which had a limited lifespan. JAXA said it was unclear why the solar cells malfunctioned, but speculated that it could be due to dust or damage caused by a hard landing.
The agency said it was trying to fix the solar cells before the batteries ran out, but also prioritized transmitting data and images from the probe while it was still operational. The data included information about the landing performance and the geological features of the landing site. The images showed that the probe was lying at an awkward angle on a slope of a crater, possibly upside down.
JAXA said it hoped that the probe would be able to recharge once the west side of the moon started receiving sunlight in the coming days. However, it also acknowledged that the chances of recovery were slim, as the low temperatures in the lunar night could damage the electronics. The agency said it would not give up on SLIM until it confirmed its status.
A new era of lunar exploration
Despite the difficulties, JAXA officials hailed the mission as a success and a milestone for Japan’s space program. They said that SLIM had proved that it was possible to land precisely on any desired location on the moon, rather than where it was feasible. This would open up new possibilities for exploring regions of scientific interest or potential resources on the moon, such as water ice or minerals.
JAXA also said that SLIM had paved the way for future human missions to the moon, as precise landing technology would be essential for ensuring safety and efficiency. Japan is part of an international consortium led by NASA that plans to send astronauts to the moon by 2028 under the Artemis program. Japan’s contribution includes developing a pressurized rover and a logistics module for a lunar outpost.
SLIM was also seen as a testbed for Japan’s domestic space industry, as it involved several private companies in its development and operation. The probe cost about 14 billion yen ($120 million), which was relatively low compared to other lunar missions. JAXA said it hoped that SLIM would inspire more innovation and collaboration in Japan’s space sector.