Japan became the fifth nation to land on the moon on Saturday, but its spacecraft ended up in a difficult position, with its engine nozzle facing space.
By design, the Japanese spacecraft, known as the Smart Lander for Investigating Moon, or SLIM, had to land on its side, a strategy to avoid tipping over on the landing site’s sloping terrain.
But about 150 feet above the ground, one of SLIM’s two main engines appears to have malfunctioned, officials from JAXA, the Japanese space agency, said Thursday.
With the on-board computer trying to compensate for the sudden loss of half the thrust, the spacecraft was still able to hit the ground at a moderate vertical speed of about 3 miles per hour. But the SLIM’s horizontal speed and landing orientation were outside of what it was designed to handle.
As a result, the spaceship rolled onto its head. It escaped the fate of some other recent robotic missions, which broke apart on the moon and its systems went haywire, communicating with Earth. But the solar panels ended up facing west, away from the lunar morning sun, and were unable to generate electricity. With the battery mostly depleted, mission controllers on Earth sent an order to shut down the spacecraft less than three hours after landing.
Despite the stumble, the mission accomplished its primary goal: a soft landing on rugged lunar terrain within 100 meters of a target landing site, far more precise than the uncertainty of miles most landers aim for.
“It successfully achieved a controlled landing,” Hitoshi Kuninaka, director general of JAXA’s Institute of Space and Astronautical Science, said in Japanese at a news conference. “We confirmed that the landing position was 55 meters away from the original target. So we came to the conclusion that we achieved the precise landing of 100 meters.”
During its brief run, an instrument on the lander took low-resolution, black-and-white images of the surrounding landscape. SLIM team members gave dog breed nicknames to rocks that caught their interest.
Two small rovers launched from SLIM shortly before landing both circled the surface of the Moon, and one of them took a picture of the overturned craft.
JAXA officials remain optimistic that SLIM could be revived in about a week, when, during the two-week lunar eclipse, the sun will shine from the west, illuminating the solar panels.
“We will try to establish communications as SLIM automatically starts operation when power generation starts,” which could allow operations to resume, Shinichiro Sakai, project manager for SLIM, said during the press conference.
If SLIM comes back to life, the lander’s instrument will make detailed measurements of the rock and soil composition.
Dr Sakai said he had “mixed feelings” about the orientation the spacecraft ended up in. “If the solar cells happened to come face down on the surface, there would be no chance of it receiving sunlight, so I’m so relieved it was left as is,” he said.
Dr Sakai said photographs taken by SLIM during its descent, before and after it partially lost thrust, showed that one of the engine nozzles had fallen off. JAXA officials are investigating what went wrong.
