Japan on Saturday became the fifth country to land on the moon, but its spacecraft ended up in an awkward position, with its engine tip hurtling toward space.
By design, the Japanese spacecraft, known as the Smart Lander for Lunar Exploration, or SLIM, will land on its side as a strategy to avoid tipping over the landing pad's sloping terrain.
But about 150 feet above the ground, one of SLIM's two main engines appeared to have malfunctioned, Japanese space agency JAXA officials said Thursday.
As the onboard computer attempted to compensate for the sudden loss of half of 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 direction were beyond what it was designed to handle.
As a result, the spacecraft rolled on its head. It escaped the fate of some recent robotic missions that were smashed to pieces on the Moon, and its systems worked in communication with Earth. But the solar panels could not generate electricity because the moon faces west away from the morning sun. With the battery mostly drained, mission controllers on Earth sent a command to shut down the shuttle within three hours of landing.
Despite the setback, the mission accomplished its primary goal: a soft landing on rough lunar terrain, within 100 meters of the target landing site, more precise than the uncertainty of miles most landers aim for.
“It successfully achieved a controlled landing,” General Hitoshi Kuninaga, director of JAXA's Space and Space Science Institute, told a news conference in Japanese. “We confirmed that the landing position was 55 meters away from the initial target. So we concluded that we achieved a 100 meter accurate pinpoint landing.
During its brief mission, an instrument on the lander took low-resolution, black-and-white images of the surrounding terrain. SLIM team members gave dog breeds nicknames for the rocks that caught their interest.
Two small rovers ejected from SLIM just before landing moved around the lunar surface, one of which took a photo of the inverted lander.
JAXA officials are hopeful that SLIM can be revived in a week, when, during the fortnightly lunar afternoon, the sun shines from the west, illuminating the solar panels.
“We will try to establish communications as SLIM automatically starts operating when power generation starts,” which would allow operations to resume, SLIM project manager Shinichiro Sakai said during a news conference.
If SLIM comes back to life, the lander's instrument will measure the composition of rocks and soil in detail.
Dr. Sakai said he had “mixed feelings” about the orientation the spacecraft ended up in. “If the solar cells were on the surface, there would be no chance of getting sunlight, so I feel very relieved. It was like that,” he said.
Dr. Sakai said photographs taken before and after SLIM's partial loss of thrust during descent show that one of the engine nozzles fell off. JAXA officials are investigating what went wrong.
