Japan became the fifth country to land on the moon on Saturday, but the spacecraft ended up in an awkward position with its engine nozzle pointing into space.
The Japanese spacecraft, known as the Smart Lunar Survey Lander (SLIM), was designed to land on its side to avoid tipping over on the slope of the landing site.
But about 150 feet above the ground, one of SLIM’s two main engines appears to have failed, officials with Japan’s space agency JAXA said Thursday.
The spacecraft was still able to impact the ground at a moderate vertical speed of about 3 miles per hour, as onboard computers tried to compensate for the sudden loss of half its thrust. However, SLIM’s horizontal velocity and landing orientation were not addressed by the design.
As a result, the spaceship flipped over. It escaped the fate of other recent robotic missions that shattered on the moon’s surface, and its systems worked and communicated with Earth. However, the solar panels were oriented westward, away from the moon’s morning sun, and were no longer able to generate electricity. With the batteries nearly depleted, mission controllers on Earth sent a command to shut down the spacecraft less than three hours after landing.
Despite the setbacks, the mission accomplished its main goals. It was far more accurate than the mile-by-mile uncertainty that most landers aim for, and would soft-land on the moon’s rugged terrain within 100 meters of the target landing site.
“The controlled landing was successful,” Hitoshi Kuninaka, director of the JAXA Institute of Space and Astronautical Science, said in Japanese at a press conference. “We confirmed that the landing position was 55 meters from the original target. We therefore concluded that we achieved a pinpoint landing with an accuracy of 100 meters.”
During the brief operation, the lander’s instruments took low-resolution black-and-white images of the surrounding landscape. SLIM team members gave breed nicknames to rocks that interested them.
Two small probes were launched from SLIM shortly before landing, both moving around the lunar surface, one of which took a photo of the lander upside down.
JAXA officials are optimistic that SLIM could be revived within about a week. Then, on a two-week lunar afternoon, the sun will shine from the west and illuminate the solar panels.
SLIM’s project manager, Shinichiro Sakai, said at a press conference, “SLIM will automatically start operating once power generation begins, so we will work to establish communications,” and said that it may be possible to restart operations.
Once SLIM is back up and running, the lander’s instruments will take detailed measurements of rock and soil composition.
Dr. Sakai said he had “mixed feelings” about how the spacecraft was ultimately oriented. “I was very relieved because if the solar cell happened to be facing down on the ground, it wouldn’t have had a chance to receive sunlight,” he said.
Dr. Sakai said photos taken before and after SLIM’s partial loss of thrust during its descent show that one of the engine nozzles fell off. JAXA officials are investigating what went wrong.