Japan became the fifth country in history to reach the moon when its spacecraft landed on the lunar surface early Saturday, officials said. But a power problem means the mission could be at risk.
Officials also said they needed more time to determine whether the spacecraft, which had no astronauts on board, achieved an accurate lunar landing – one of the mission's priorities.
Hitoshi Kuninaka, director of the Institute of Space and Astronautical Sciences, said he believes the rovers were launched from the spacecraft and that data was transmitted to Earth from the Smart Lander for Investigating Moon (SLIM).
But he said the SLIM's solar battery produces no electricity and the ship's battery life would only last a few hours longer. He said the priority now is for the spacecraft to collect as much lunar data as possible from the remaining battery.
Japan therefore follows the United States, the Soviet Union, China and India in their search for the moon.
Mr. Kuninaka believes the Japanese space program has achieved at least “minimal” success.
The SLIM spacecraft landed on the moon at around 12:20 a.m. Tokyo time on Saturday.
The wait for news has been long after the Japanese Space Agency's (JAXA) mission control initially said SLIM was on the lunar surface but was still “checking its status.” No further details were released until a news conference nearly two hours later.
For the mission to be considered fully successful, agency officials must confirm whether SLIM performed a “precise lunar landing.” Mr. Kuninaka said that even if more time were needed, he personally believes that this precise lunar landing was likely successful, based on his observation of the data showing the spacecraft's movement until landing.
SLIM, aimed at a very small target, is a lightweight spacecraft the size of a passenger car. “Precision landing” technology was used, which promises far better control than any previous lunar landing.
While most previous probes used landing zones about 10 kilometers wide, SLIM aimed at a target just 100 meters away. This project is the culmination of two decades of JAXA work in precision technology.
As the spacecraft descended, mission control at the Japan Aerospace Exploration Agency reported that everything was going according to plan and later stated that SLIM was “on the lunar surface.” But it has not been clear since then whether the moon landing was successful.
A “precision moon landing” technique
According to the space agency, SLIM began its descent at midnight on Saturday and was about 10 kilometers above the lunar surface within 15 minutes.
At an altitude of five kilometers, the lander was in vertical descent mode, and at 50 meters SLIM should then make a parallel movement to find a safe landing point, JAXA said. About 30 minutes after the suspected moon landing, JAXA said it was still assessing the condition of the spacecraft.
The mission's main goal is to test new landing technologies that would allow lunar missions to land “where we want them, rather than where it's easier to do so,” JAXA said. If the landing is successful, the space probe will search for clues about the origin of the moon and, among other things, analyze minerals using a special camera.
The SLIM, equipped with a cushion to cushion the impact, was expected to land near Shioli Crater, near a region covered in volcanic rock.
The closely watched mission came just 10 days after a lunar mission led by a private American company failed when the spacecraft developed a fuel leak hours after the rocket's launch.
SLIM was launched in September using a Mitsubishi Heavy H2A rocket. The spacecraft initially orbited the Earth and entered lunar orbit on December 25th.
Japan hopes that success will allow it to regain confidence in its space technology after several failures. A spacecraft designed by a Japanese company crashed during an attempted moon landing in April, and a new flagship rocket failed on its first launch in March.
JAXA has a good record of “difficult landings.” Its Hayabusa2 spacecraft, launched in 2014, landed twice on the 900-meter-long asteroid Ryugu and collected samples that were returned to Earth.
SLIM carries two small autonomous probes: the rover vehicles LEV-1 and LEV-2, which should be released shortly before the spacecraft lands. LEV-1, equipped with an antenna and a camera, was intended to record SLIM's lunar landing. LEV-2, on the other hand, is a spherical rover equipped with two cameras, developed by JAXA in collaboration with Sony, toy maker Tomy and Doshisha University.