Japan’s Moon Sniper: JAXA has a bag of clever tricks to ensure SLIM module’s successful landing

In an effort to recover from past challenges and strengthen its space program, Japan launched the “Moon Sniper” mission last Thursday, shortly after India’s remarkable lunar achievement with the Chandrayaan-3 mission.

So far only the United States, Russia, China, and India have had prosperous lunar landings to date. Because of this, Japan’s mission is imbued with great optimism and noteworthy technological progress.

Japan for its part, has really crafted its lunar lander with expertise to give it the best chance of a successful landing. It wouldn’t be far-fetched to say that like ISRO’s Chandrayaan-3, JAXA’s SLIM or Smart Lander for Investigating Moon mission is an engineering marvel

What makes landing on the moon difficult
The Moon shows significantly lower gravitational force compared to Earth. Furthermore, its sparse and delicate atmosphere, coupled with the presence of lunar dust, presents formidable obstacles for any spacecraft, light or heavy, attempting to land.

Even the smallest particle of dust can exert a substantial impact on the regulation of temperature and the optical functionality of equipment situated on the lunar surface. It can cause significant damage to the external instruments such as sensors and cameras when a spacecraft is descending.

Furthermore, because the Moon is at a considerable distance from the Earth, issues always crop up in deep-space communication. The instruments on board, even though they are tested heavily, always have a chance of failing for n number of reasons. Plus, at that distance, radio signals also face an issue because of interference from the Sun’s rays, as well as the atmosphere and gravity of the moon.

Precision Landing
What Japan has done to mitigate all of this, is really clever. They are actually sending a very small probe to the moon. The main objective of the SLIM mission is not to collect a lot of data but to test whether Japan can achieve what is called a precision landing. Hence the mission’s nickname, Moon Sniper.

Precision Landing or Precise Landing is when a module lands on any celestial surface within 100 metres of a predesignated spot.

Most landing modules have a contingent landing spot that is usually about hundreds of kilometres, away, when we consider the Moon. Chandrayaan-3, for example, had a backup landing spot about 400-450 km away from its final Shiv Shakt Point.

Precision landings are important for a number of reasons. In recent years, our understanding of celestial bodies targeted for exploration has grown substantially. The objectives of future missions will become increasingly specific. As a result, it is no longer sufficient to merely land on celestial bodies but to land at very precise spots.

Furthermore, future solar system scientific exploration will need advanced observation equipment. It becomes imperative to reduce the overall weight of the systems and allocate resources efficiently to accommodate newer and more sophisticated observation tools.

How JAXA’s SLIM Module is an engineering marvel
The main objective of the SLIM mission is not to collect too much data, but to test if they can land a module within 100 metres of a very specific spot.

The entire landing module is just slightly bigger than the Pragyan Rover, and considerably smaller than the Vikram Lander module. The SLIM lander module has a mass of less than 120 kg. Compared to that, the Vikram lander, without the Pragyan Rover, had a mass of 1750 kg.

Most spacecraft land where they’re told to and have a very limited ability to survey the terrain beneath them and select a safe spot to touch down. Japan’s SLIM module on the other hand is equipped with state-of-the-art high-resolution cameras. Its onboard computers are already preloaded with detailed models of the Moon’s surface, specifically the near side of the moon close to Mare Nectaris, a lunar basin that is one of the visible dark spots on the moon.

These sophisticated computers are programmed with algorithms that enable them to meticulously analyze data received from the cameras and autonomously determine the most suitable landing site for the spacecraft. Think of it as a smart, driverless car, trying to find a parking spot for itself.

SLIM also includes a pair of rovers that will be released from the lander. The first of these weighs a mere 250 grams and has the unique capability to transform from a spherical shape into a cylinder. This rolling rover, known as the Palm-Sized Lunar Excursion Vehicle 2 or LEV-2, will be deployed as SLIM goes into free fall on its descent to the lunar surface. Throughout its brief operational life of 1 day, it will capture images of the Moon, SLIM, and try to traverse the lunar terrain.

These images will then be transmitted to the Lunar Excursion Vehicle 1 (LEV-1), which possesses the capability to make short hops across the lunar surface. LEV-1 can establish direct communication with Earth, facilitating the relay of valuable data from these lunar probes.