Japan’s SLIM moon lander enters lunar orbit

The Japan Aerospace Exploration Agency (JAXA) has announced that its ‘Smart Lander for Investigating Moon’ (SLIM) successfully entered the moon’s orbit on Monday. This accomplishment marks a pivotal advancement toward Japan’s historic and impending lunar landing, anticipated to take place next month.

“On Monday, SLIM successfully entered the moon’s orbit at 04:51 p.m. Japan time (0751 GMT),” JAXA said in a statement released Monday evening.

The SLIM is nicknamed the “Moon Sniper” because it is designed to land within 100 meters (328 feet) of a specific target on the lunar surface.

If successful, the touchdown would make Japan only the fifth country to have successfully landed a probe on the moon, after the United States, Russia, China and India.

“Its trajectory shift was achieved as originally planned, and there is nothing out of the ordinary about the probe’s conditions,” JAXA said.

The lander’s descent toward the moon is expected to start around 12:00 a.m. Japan time on January 20, with its landing on the surface scheduled for 20 minutes later, JAXA said.

The H-IIA rocket lifted off in September from the southern island of Tanegashima carrying the lander, after three postponements linked to bad weather.

SLIM was inserted into an elliptical lunar orbit connecting the Moon’s south and north poles with a period of about 6.4 hours. Its altitude will be about 600 kilometres at the point closest to the Moon (perilune) and 4,000 kilometres at the point furthest away from the Moon (apolune).

From now until mid-January 2024, the Japanese space agency will lower the apolune point. The perilune point will also be lowered to an altitude of 15 kilometres on January 19. The lander will start descending towards the moon on January 20.

JAXA said this month that the mission would be an “unprecedentedly high precision landing” on the moon.

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The lander is equipped with a spherical probe that was developed by a toy company. Slightly bigger than a tennis ball, it can change its shape to move on the lunar surface.

Compared to previous probes that landed “a few or 10-plus kilometers” away from targets, SLIM’s purported margin of error of under 100 meters suggests a level of accuracy once thought impossible, thanks to the culmination of a 20-year effort by researchers, according to JAXA.

With the advance of technology, demand is growing to pinpoint targets like craters and rocks on the lunar surface, Shinichiro Sakai, JAXA’s SLIM project manager, told reporters this month.

“Gone are the days when merely exploring ‘somewhere on the moon’ was desired,” he said.

Hopes are also high that SLIM’s exactitude will make sampling of the lunar permafrost easier, bringing scientists a step closer to uncovering the mystery around water resources on the moon, Sakai added.

Japanese missions have failed twice—one public and one private.

Last year, the country unsuccessfully sent a lunar probe named OMOTENASHI (outstanding moon exploration technologies demonstrated by a nano-semi-hard impactor) as part of the United States’ Artemis 1 mission.

In April, Japanese startup iSpace tried in vain to become the first private company to land on the moon, losing communication with its craft after what it described as a “hard landing.”