How Japan joined the elite by pulling off soft Moon landing

Japan becomes only fifth nation to touch down on lunar surface, following string of recent international failures

An artist's illustration of the Slim landing on the Moon. EPA
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Japan carried out a successful Moon landing this weekend after a string of failed attempts by others in recent years.

Jaxa, its national space agency, lowered its Smart Lander for Investigating the Moon (Slim) on to the lunar surface on Saturday, becoming only the fifth country to achieve the feat.

Similar attempts were made in 2019 by India and Israel, Russia in 2022, by Japanese company ispace last year and an American company this year, but all failed.

Only the US, the former Soviet Union, China, India in 2023 and now Japan have managed to softly touch down on the lunar surface.

“Slim has made it to the Moon’s surface. It has been communicating with our ground station and responding to commands from Earth accurately,” Hitoshi Kuninaka, vice president of Jaxa, said after the landing.

How did Japan do it?

Japan's Slim used precision-landing technology that allowed it to touch down close to the target spot on the surface.

It is a lightweight probe that was sent to the Moon so engineers can improve the technology for exploration missions.

"By creating the Slim lander, humans will make a qualitative shift towards being able to land where we want and not just where it is easy to land, as had been the case before," said Jaxa.

"By achieving this, it will become possible to land on planets even more resource-scarce than the Moon."

The vehicle's solar cells were not working after the landing, leaving Slim relying on battery power, but mission control is still receiving data.

Why are lunar landings difficult?

Moon-landing vehicles cannot use parachutes to slow for a touchdown as they can on Earth and Mars.

Instead, they need to use thrusters to brake and adjust their positioning to land softly on the surface.

Mojtaba Akhavan-Tafti, a space scientist at the University of Michigan, told The National that Moon landings are challenging but computers are "getting smarter now and sensors more reliable".

"For a robot to successfully land, especially if there are no operators in the loop to help make decisions, everything must go right," he said.

"We have to already have a very good understanding of the environment in which the mission will operate, including lunar atmosphere, which determines drag, lunar geophysics, including gravity and terrain."

Lunar terrain is unpredictable, with many craters that can make landing difficult.

Mr Akhavan-Tafti said braking properly during a landing attempt is also important.

"The lander approaches the lunar surface at hundreds of metres per second [2,438 metres per second for Apollo] and then needs to slow down to a fraction of one metre per second [0.3 metres per second in the case of the Apollo lander]," he said.

The Hakuto-R Mission 1 lander by ispace, which was also carrying the UAE's Rashid rover, crashed on the Moon because its software miscalculated its altitude.

Moments before touchdown, the vehicle ran out of fuel, causing a hard landing.

Russia's Luna-25 craft also crash landed on the surface, after a planned manoeuvre did not go as planned.

Updated: January 22, 2024, 12:07 PM