Japan has achieved a historic feat in lunar exploration by becoming the fifth nation to land a spacecraft on the Moon. The Smart Lander for Investigating Moon (SLIM) mission successfully touched down on the lunar surface on January 19, 2024, after four months of journey from Earth. However, the mission faced some technical challenges that might have cut short its operation time.
SLIM: A Moon Sniper
SLIM was designed to demonstrate a new image-based automatic navigation system that could enable a precise landing within 100 metres of its target zone. This is a significant improvement from previous ranges of a few to dozens of kilometres. SLIM used vision-based navigation technology, which imaged the surface as it flew over the Moon, and located itself quickly by matching the images with onboard maps.
The car-sized, 200-kilogram spacecraft aimed to land on a 15-degree slope outside Shioli crater, south of the lunar equator, in a two-step manner. It was supposed to hit the slope first with one leg at the back of the craft before tipping forward and stabilizing on the four front legs. This would allow it to study the geological features of the landing site, which is thought to be rich in volcanic material.
A Bittersweet Success
According to Hitoshi Kuninaka, vice president of Japan Aerospace Exploration Agency (JAXA), SLIM has very likely achieved its primary goal of landing on the Moon with an unprecedented accuracy. Telemetry data showed that SLIM touched down in its target area near Shioli crater and communicated with Earth accurately.
However, it seems that the solar cells on the spacecraft were not generating electricity at this point, and SLIM was operating solely on its battery. “The battery will last several more hours — those hours will be the remaining life of SLIM,” Kuninaka said at a press conference after the landing was completed. He said the agency will continue to monitor the lander, because there is still a chance that the panels could start working again.
SLIM also carried two small rovers that were deployed just before landing. The rovers, named Kikai and Hakuto-R, were designed to conduct experiments on the lunar surface, such as measuring temperature and radiation levels. JAXA officials said both rovers were successfully deployed and were functioning normally.
A Big Win for Asia
Despite the power issue, SLIM’s landing marks a significant achievement for Japan in the field of lunar exploration, showcasing the nation’s commitment to advancing space technology. Japan has previously sent orbiters and impactors to the Moon, but this is its first soft landing.
Japan is also the fifth country to land on the Moon after the former Soviet Union, the United States, China and India. Only China, India and Japan have put a spacecraft on the Moon in the past decade. India successfully landed one last August.
Namrata Goswami, a space-policy researcher at Arizona State University in Phoenix, says the successful landing is “a big win for Asia”. She adds that Japan’s precision landing technology could pave the way for future missions to explore more challenging sites on the Moon, such as craters and caves.