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The Land of the Rising Sun could soon land on the Moon.
Key points:
- JAXA's SLIM spacecraft is set to attempt a Moon landing on January 20
- The spacecraft's autonomous descent is aided by onboard cameras and artificial intelligence
- If successful, SLIM would make Japan the fifth nation to complete a soft landing on the Moon
A spacecraft built by the Japan Aerospace Exploration Agency, or JAXA, has been circling Earth's only natural satellite since Christmas, preparing for a historic touchdown attempt on Saturday, January 20, Japan time.
Smart Lander for Investigating Moon, better known as SLIM, is about the size of a small car and was launched on September 7, 2023. It's the first JAXA-built spacecraft to attempt a soft landing on the Moon.
Like previous Moon landing attempts, SLIM's descent will be fully autonomous but getting to the surface is no easy feat.
The Moon is a wasteland strewn with rocks and boulders, and pockmarked by craters.
To navigate, JAXA has equipped SLIM with a suite of cameras and onboard artificial intelligence designed to pick out hazards and pinpoint a landing.
Recent history shows just how difficult Moon landings can be. Three private companies — Japanese robotics firm ispace, Israel's ILspace and US company Astrobotic — have attempted landings in the past five years. The first two crash landed on the Moon. Astrobotic won't get there at all.
If SLIM can manage to pinpoint a landing, it will make Japan the fifth nation to land on the Moon following the US, the USSR, China and India.
Can we expect it to succeed? And what will scientists learn should SLIM make it to the Moon?
What is SLIM?
SLIM is a multi -legged lander covered in gold and solar panels weighing in at a touch over 200kg (without propellant). Compare that to the Apollo 11 lunar module which clocked in at roughly 4,300kg.
In press materials, it has been dubbed a "Moon sniper", which makes it sound much more menacing than its cute mascot suggests.
But the name fits: SLIM's primary mission is to demonstrate a pinpoint landing technique.
"Scientists no longer want to land somewhere within a wide region, but by a particular rock," sub-project manager of the SLIM mission, Kushiki Kenji, said.
You might think about landing on the Moon like going to the supermarket. You want to park your vehicle close to the supermarket doors, so you can get in, get what you need and get out.
Typically, landing on the Moon has been more like parking two suburbs away.
"When Armstrong landed on the Moon, he had a landing area of about 20 square kilometres," Brad Tucker, an astrophysicist at the Australian National University, said.
"SLIM is aiming for 100 square metres."
In short, the spacecraft is designed to forgo the car park altogether. Instead, it's attempting to land in the right aisle.
If successful, SLIM will take the first giant leap for small, light spacecraft to one day land on the varied surfaces that cover bodies across our Solar System — and will become especially important if crewed missions begin to leave Earth for the Moon or Mars.
"We are going to want to land close by any potential resources to investigate in preparation for a human crew," Dr Kenji said.
Also on board SLIM is SORA-Q, a ball-shaped rover partly developed by Japanese toy giant Tomy.
It will be released during descent and examine the lunar surface near SLIM's landing zone until its batteries run flat, after about two hours.
When is SLIM going to touchdown on the Moon?
The exact timing of touchdown is expected to be at 00:20am on January 20, Japan Standard Time.
For most Australians, that means 2:20am AEDT, or a more palatable 11:20pm on January 19 for those in Western Australia.
Can I watch the SLIM landing attempt?
Unfortunately, SLIM won't have a live, rolling video feed like Apollo 11 did back in 1969, with video footage beamed back from the surface.
However, there is a livestream of the control room operations at JAXA headquarters during the landing operation.
SLIM will be taking still images of the surface via small probes so you can expect to see those beamed back to Earth relatively quickly.
How will the landing work?
On January 19, SLIM's orbit will be lowered to within 15km of the surface before the descent phase starts at midnight on January 20.
The spacecraft will swivel into a vertical position, its "smart eyes" facing the lunar surface, and begin to descend.
There will be no human control over the landing sequence. Like other missions, once engineers send the signal to land, it's up to the spacecraft's onboard computing system to take over.
The onboard AI will ensure it finds a safe landing zone among the Moon's many craters, boulders and rocks.
It's able to do so because our understanding of the lunar surface has been greatly improved by orbiter missions, like NASA's Lunar Reconnaissance Orbiter (LRO) and JAXA's own Kaguya mission, since the Apollo missions.
"SLIM is equipped with 'smart eyes' that use image matching to identify craters on the lunar surface below the spacecraft and match these to onboard maps from Kaguya and LRO to ascertain a precise location, and autonomously navigate to the target landing site," Dr Kenji said.
SLIM will constantly fire its engines to adjust as it tries to safely bring itself to the lunar surface.
To complicate matters, SLIM will land on a region of the Moon with a slight incline. This could be perilous for some spacecraft, but SLIM is designed to make light work of a slope.
As it reaches the surface, it will make first contact with the Moon via its rear leg. Then it will fall onto its two front legs.
All legs are equipped with a lattice-like aluminium shock absorber pad, which should take the brunt of any forceful impact.
In total, the landing should take around 20 minutes. In a statement, Dr Kenji dubbed this, "a breathless, numbing 20 minutes of terror!"
Where is SLIM landing?
The SLIM landing site is near the Shioli crater, just next to Mare Nectaris, or the "Sea of Nectar", a darkened region of the Moon's surface formed by the cooling of volcanic rock.
The rock around Shioli was 1 to 2km below ground before it was brought to the surface by a meteor impact. It holds clues to the Moon's history and its formation.
This region was chosen as a landing site because observations suggest Shioli rocks bear large amounts of olivine, a green mineral containing iron, magnesium, silicon and oxygen.
If landing is successful, SLIM's spectral camera will investigate the chemical composition of these rocks, hoping to determine the ratio of iron and magnesium in olivine.
What are SLIM's chances of success?
The recent failures of private Japanese robotics company ispace, Russia's Luna 25 mission and US company Astrobotic's Peregrine mission highlight the small margin for error when you're operating in space.
"Mostly the secret is testing," Dr Tucker said.
He explained that thorough, repeated testing to ensure the failure points are well understood and planned for will put JAXA in a good position to stick the landing.
According to Dr Kenji, "everything has been smooth up to now.
"Now the feeling is: This is not a drill."
Japan's ambitious interplanetary exploration missions
JAXA doesn't receive the blanket media coverage that its US counterpart in NASA receives, but it has made quite a name for itself in exploring the Solar System. Deputy director general of JAXA's Institute of Space and Astronautical Science, Masaki Fujimoto, said hopes SLIM will build on its success.
"SLIM will demonstrate two key technologies that will open a new horizon in Moon and Mars exploration," he said.
In 2010, it returned scant samples of the asteroid Itokawa to Earth upon completion of the Hayabusa mission. It followed that with the Hayabusa2 probe, which visited the asteroid Ryugu and returned samples to Earth in 2020, landing in a remote part of the South Australian outback, just outside Woomera.
It's likely JAXA will attempt a similar return mission in the next decade. Its Martian Moon eXploration (MMX) mission is headed to Phobos, a potato-shaped rock that orbits the red planet.
Around 2026, MMX will be launched and JAXA expects it to return with samples from Phobos sometime after 2029. The technologies being trialled during the SLIM mission may be used in those future missions, as well as new missions to the lunar south pole.
But now we're getting a few steps ahead of ourselves.
Safely touching down on the Moon is hard. On January 20 — after 20 minutes of terror — Japan will find out if it has succeeded in doing so.
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