- Written by Jonathan Amos
- Science match
Artwork: JAXA becomes the fifth national space agency to land on the moon
A Japanese robot has successfully landed on the moon, but problems with its solar power system mean the mission may only last a few hours.
The Intelligent Lunar Examination Lander (Slim) gently positions itself on the lunar surface near an equatorial volcanic crater.
This achievement made the Asian country the fifth country to land smoothly on the Earth's natural satellite, after the United States, the Soviet Union, China and India.
But engineers are now struggling to save the mission.
For reasons that are not yet fully understood, the vehicle's solar cells will not be able to generate electricity.
This leaves the Slim fully connected to its batteries and they will eventually discharge. When they do this, the vehicle will become silent. He will not receive orders and will not be able to talk to Earth.
Engineers are currently prioritizing activities.
They have turned off the heaters and are pulling photos from the vehicle. They're also retrieving data that will tell them how successful the landing program has been.
JAXA officials would not immediately abandon Slim if he remained silent. It's always possible that the solar cells are somehow oriented in a way that prevents them from seeing the sun.
Officials said that with the changing angles of light on the moon, it is possible that Slim will return to life.
The Japanese public celebrated the country's soft landing
Asked at a news conference whether Japan could justifiably demand a soft landing, Hitoshi Kuninaka, vice president of JAXA, said it was possible.
“If the automated landing had not been successful, there would have been a collision with the surface at a very high speed and the function of the spacecraft would have been completely lost,” he told reporters.
“But it still sent the data back to us correctly, which means our original goal of a soft landing was successful.”
Slim was carrying two small rovers and telemetry indicates that he was able to eject them as planned just before landing.
The rover, carrying an infrared camera, was scheduled to spend the next two weeks studying the local geology. How much of this investigation can be accomplished in the time available is uncertain.
Artwork for the two deployed rovers: a hopper (L) and a shape-shifting roller (R)
Statistically, it has proven very difficult to land on the Moon. Only about half of the attempts succeeded.
JAXA has placed its trust in new precision navigation technologies.
The lander's on-board computer used rapid image processing and crater mapping to avoid hazards reaching the landing point.
The engineers wanted to get within 100 meters (330 feet) of their target location and will now study the data to see how well the Slim performed. But early indications are that the technologies worked as designed.
“Looking at the tracking data, I think Slim definitely achieved an accurate landing with an accuracy of 100 metres. Of course, as we previously informed you, it will take about a month to accurately analyze the information,” Kuninaka said.
Slim began his descent maneuvers from an altitude of 15 kilometers (9 miles) at midnight on Saturday, Japanese standard time (15:00 GMT, Friday). The landing occurred just after 15:20 GMT.
The landing site, near Shiuli Crater, is currently bathed in sunlight, but the darkness of the lunar night will return there at the end of the month.
When this happens, temperatures will drop to levels that are very capable of breaking circuit boards.
The target landing site was on the slopes near Xiuli Crater, which is located just south of the Moon's equator.
JAXA has successfully landed robots on asteroids twice, so landing on the moon is another feather in its cap.
They will play important roles in NASA's Artemis programme, which seeks to return humans to the moon's surface after a gap of more than half a century.
Last year, a private Japanese company, iSpace, tried to land. The Hakuto-R crashed when the onboard computer became confused about its altitude above the moon.
The private American company Astrobotic on Thursday jettisoned the Peregrine lander into the Earth's atmosphere. A propulsion error prevented her from attempting a landing.
Dr Simon Barber of the Open University in the UK had tools for Peregrine.
He praised the Japanese efforts.
He told the BBC: “For me, it was all about the precise landing. This is a huge success. I would be really happy if I were in their shoes.”
“We're in an era where there's a lot of lunar missions happening with a lot of different players. If we bring together all this knowledge, which all these players are gaining through these attempts — whether they're successful or not — we learn as a society how to put missions together more successfully in the future.”
Likewise, Dr. Emma Gatti, of digital magazine SpaceWatch Global, said Japan had a lot to celebrate: “It's historic for them; it's a matter of prestige. It's important for Japan as a country; it's important for all the investments they have.” This is evidence that it can be done by a country not the size of China or the United States.”
