Its descent speed is said to be 6,400 km/h, which is seven times faster than an airplane.

In the early hours of the 20th, JAXA (Japan Aerospace Exploration Agency)'s unmanned spacecraft ``SLIM'' will attempt to land on the moon, which requires precise control.

Last year, a Japanese venture company's lander attempted to do so, but it fell to the moon's surface and failed.

If successful this time, it will be the first time in Japan.

We have summarized how to land on the moon and this mission.

The landing schedule is


SLIM is an unmanned spacecraft operated by JAXA (Japan Aerospace Exploration Agency) whose main purpose is to demonstrate precise landing technology on the lunar surface.

The height is approximately 2.4 meters and the weight excluding fuel is approximately 200 kg.

By applying image recognition technology, which is used to recognize people's faces with digital cameras, the aim is to identify topographical information such as craters on the moon and land at the target location within 100 meters. ing.

It was launched from the Tanegashima Space Center in Kagoshima Prefecture in September last year, and has been flying toward the moon, about 380,000 kilometers away, over a period of about four months.

After changing its orbital altitude at around 10:40 pm on the 19th of this month, it plans to begin its descent for landing at around midnight on the 20th, taking approximately 20 minutes to land.

7 times faster than an airplane

The speed of ``SLIM'' when it begins its descent is approximately 6,400 km/h, which is seven times that of an aircraft.

By injecting in the opposite direction to the direction of travel, it rapidly decelerates and aims for a landing site approximately 800 kilometers away.

Until the landing site, the onboard camera takes images of the moon's surface, extracts the shapes of craters, etc., and compares them with map data.

It estimates the aircraft's position, corrects any deviations, and approaches the aircraft while controlling it using image matching navigation to land more accurately.

As it approached the landing site, it descended further from an altitude of approximately 3.5 km while checking the altitude and obstacles.

The plan is to separate the two small robots as they approach the moon's surface before landing.

Pinpoint landing using new technology

The moon's surface has craters and other areas, and the topography is complex in some places.

Landing is more difficult on sloping or uneven terrain, so until now it has been common practice to land on flat areas with few obstacles.

The planned landing site for SLIM this time is near a crater called SHIOLI, on a slope of approximately 15 degrees.

When landing on a slope, the team plans to use a new technique called a ``two-stage landing method,'' which involves landing while falling down.

Simulation of “two-stage landing method”

The "two-stage landing method" uses five short landing legs equipped with shock absorbing materials, and the main landing gear touches down on the lunar surface while tilting the aircraft forward, then it falls down and uses the auxiliary landing gear to stabilize the landing. This allows the aircraft to land safely even on slopes.

``SLIM'' Project Shinichiro Sakai Project Manager

``In the past, the image of landing is to stand and spread your legs to avoid falling, but in ``SLIM,'' you purposely fall down and land on your knees or hands to avoid falling. There's no other example like this that I know of, so it's a pretty unique method."

Furthermore, this time, the aim is to make a "pinpoint" landing, keeping the difference in distance between the planned landing point and the landing place within 100 meters.

Previous probes from various countries had errors on the order of several kilometers, so this will be a much more accurate landing.

According to JAXA, the success or failure of the moon landing will be known by dawn on the 20th, but whether or not the "pinpoint landing" was successful within 100 meters will not be determined until about a month after carefully examining the data. It will be announced.

"I feel that 'pinpoint' landing is a technology that will definitely be needed in the exploration of the moon and other celestial bodies in the future. We have been thinking about it through simulations and other methods, but I am not sure if we have really overlooked anything. But I think, the last 20 minutes before landing will be a long 20 minutes and a short 20 minutes for us."

Mission after landing “Exploring the origin of the moon”

After landing, SLIM will conduct an exploration to discover the origin of the moon.

The key to exploration is a special camera weighing about 4 kg called a ``multiband camera'' developed by a team including JAXA, Ritsumeikan University, and the University of Aizu.

multiband camera

The ``multiband camera'' installed in ``SLIM'' is equipped with 10 types of special filters, and by analyzing the wavelength of the reflected light, the type and composition of minerals can be determined.

Regarding the birth of the Moon, the ``Giant Impact Theory'' is considered to be most likely, which states that it was formed approximately 4.6 billion years ago when another celestial body collided with the Earth. It is believed that the moon was created by scattering the moon.

In the area where we plan to land this time, olivine, a type of mineral that once existed inside the moon, is thought to be exposed on the surface, confirming that the composition of the moon's mantle is similar to that of Earth. If this happens, it will be one piece of evidence supporting the "giant impact theory."

The camera will no longer be usable if the moon's surface temperature rises due to the sun's heat, so it is expected that measurements will only be possible for a few days after landing.

Last November training session

Since smooth operation within a limited time is the key, a training exercise simulating camera operation was held in Shiga Prefecture last November.

During the training, participants learned how to move the same type of camera and change the area it captures, as well as how to remotely adjust brightness and other settings based on the data captured by the camera.

Kazuto Saeki, director of the Ritsumeikan University Space and Earth Exploration Research Center, said

, ``Although there are various theories regarding the origin of the moon, humans have never observed the moon's mantle, and much remains unknown. The exploration results will have a major impact on the models of many researchers who consider the origins of the Moon and Earth."

SLIM is also equipped with two small robots, which will separate just before landing and use their respective wide-angle cameras to take pictures of the lunar surface. .

Competition heats up over “moon water”

During the Cold War between East and West, exploration of the moon was actively conducted from the end of the 1950s to the mid-1970s, with the former Soviet Union's Luna program and the United States' Apollo program.

After that, in response to a series of papers published in recent years showing that there is a high probability that water exists in the form of ice in places where sunlight does not shine, such as the north and south poles of the moon, Exploration efforts are intensifying in each country to make it a base for space exploration.

Last August, India landed its lunar probe Chandrayaan-3 near the moon's south pole, making it the fourth country in the world to successfully land on the moon, after the former Soviet Union, the United States, and China.

Private companies are also developing a lunar lander, but none of them have succeeded in landing, but an American private company launched a lunar lander on the 8th of this month, and in April last year, a Japanese lunar lander was launched. The venture company ``ispace'' also launched a lunar lander and attempted to land it.

The ``iSpace'' lander had failed to land due to incorrectly recognizing the altitude, and measures such as improving the altitude recognition system were taken to prevent the next launch from occurring. The company aims to become the world's first private company to land on the moon.

In addition, the United States is leading an international project called the Artemis Project, which aims to use the moon as a stepping stone for humankind's expansion into space.

The aim is to carry out manned exploration of the moon's surface for the first time in about half a century since the Apollo program, and the spacecraft Orion, which was launched without any astronauts on board as the first step, will orbit the moon for 25 days. It conducted a test flight and returned safely.

In addition to constructing a new space station called "Gateway" that will orbit the moon as a relay base for future exploration of the moon and Mars, we plan to have astronauts land on the moon by September 2026. The plan is to do so.

JAXA's unmanned spacecraft ``SLIM'' takes on the challenge of landing on the moon as international competition intensifies.

Will Japan be able to demonstrate its presence by successfully landing on the moon with high precision?

A notable challenge looms.

(Science and Culture Department reporter Mizuki Hirata)