Power drain | Why Japan’s moon mission may hit a speed-breaker

Japan became the fifth country in history to reach the moonwhen its spacecraft landed on the lunar surface early on Saturday (January 20), officials said. Japan follows the United States, the Soviet Union, China, and India in landing a spacecraft on the moon’s surface.

The mission’s total success could however be in jeopardy because of a power supply problem.

Mission objectives

One of the objectives of the mission was to achieve a soft landing on the moon, which it did successfully.

Another priority of the mission was for the Smart Lander for Investigating Moon (SLIM) to make a pinpoint landing, and officials of JAXA (the Japanese space agency) said they needed more time to analyse whether this objective was achieved. For the mission to be considered fully successful, space officials need to confirm whether it made a pinpoint landing.

SLIM, which was aiming to hit a very small target, is a lightweight spacecraft about the size of a passenger vehicle. It was using “pinpoint landing” technology that promises far greater control than any previous moon landing. While most previous probes have used landing zones about 10 kilometres wide, SLIM was aiming at a target of just 100 meters.

Main goal

The mission's main goal is to test new landing technology that would allow moon missions to land “where we want to, rather than where it is easy to land,” JAXA has said.

Hitoshi Kuninaka, head of Japan’s Institute of Space and Astronautical Science, said while more time is needed, he personally thinks it was most likely achieved, based on his observation of data showing the spacecraft's movement until the landing.

JAXA has a track record with difficult landings. Its Hayabusa2 spacecraft, launched in 2014, touched down twice on the 900-metre-long asteroid Ryugu, collecting samples that were returned to Earth. Experts say a success of SLIM's pinpoint landing, especially on the moon, would raise Japan's profile in the global space technology race.

Accuracy of landing

Takeshi Tsuchiya, aeronautics professor at the Graduate School of Engineering at the University of Tokyo, said it was important to confirm the accuracy of landing on a targeted area for the future of moon explorations.

“It is necessary to show the world that Japan has the appropriate technology in order to be able to properly assert Japan's position in lunar development. The moon is important from the perspective of explorations of resources, and it can also be used as a base to go to other planets, like Mars,” he said.

The third objective of the moon mission was to seek clues about the origin of the moon, including analysing minerals with a special camera. The SLIM, nicknamed "the Moon Sniper," is equipped with a pad to cushion impact, and was aiming to land near the Shioli crater, near a region covered in volcanic rock.

Power supply problem

However, the mission could be in jeopardy because of an unfortunate occurrence. The scientists have realised that SLIM’s solar cell is not generating sufficient power and the battery may last only for a few more hours. They are trying to gather as much data as possible before the battery’s remaining power is consumed.

There was a tense wait for news after the Japan space agency's mission control initially said that SLIM was on the lunar surface, but that it was still “checking its status.” No further details were given until a news conference nearly two hours later.

“SLIM has been communicating to the Earth station and it is receiving commands from the Earth accurately and the spacecraft is responding to these in a normal way,” said Kuninaka.

“However, it seems that the solar cell is not generating electricity at this point in time. And since we are not able to generate electricity, operations are relying on battery power,” he added.

Japan’s second attempt

This is Japan’s second attempt to land a spacecraft on the moon. In April 2023, a Japanese company called ispace reportedly failed in its lunar mission, after it lost contact with its lander. It would have been the first private firm to land a spacecraft on the moon’s surface.

Japan is developing a lunar rover with Toyota that would transport astronauts to the moon. The scientists were hoping to use the data collected by the SLIM lander and its probes in preparing for this crucial mission.

The country is also planning to launch a rover to the moon’s south pole next year to discover potential sources of lunar water. This mission is in collaboration with ISRO, which will supply the lander module.