The Japanese SLIM lander successfully entered lunar orbit

SLIM (Smart Lander for Investigating Moon) is a small lander launched on September 7 from Japan. Since that day, it headed towards the moon on a long path, covering a distance of 1.5 million kilometers from Earth before returning to the moon. On December 25, the Japanese space agency JAXA announced that the lunar orbit entry maneuver had been successful.

SLIM is therefore in its first orbit around our satellite, which will be adjusted in the coming weeks to get closer to the satelliteThe moon landing, currently scheduled for January 19 15:00 UTC (16:00 in Italian).

SLIM is the third mission for this target launched between July and September, after Luna-25 and Chandrayan-3. The Japanese mission will aim to demonstrate JAXA's techniques and processes for properly landing on the lunar surface, as is the case with the Indian mission.

In fact, even Japan has never been able to descend to the surface of our satellite properly. SLIM carried out a flight similar to that attempted by ispace's own (also Japanese) Hakuto-R lander at the beginning of 2023, whose lunar landing failed due to a problem with the terrain analysis and surveying software in April 2023.

SLIM lunar orbit and next steps

SLIM entered lunar orbit on December 25 at 08:51 Italian time (16:51 in Japan). It is now at the Apollonium point (the farthest point in orbit from the Moon) at a distance of 4,000 km and the Perilonium point (the closest point) at a distance of 600 km. This path is indicated in blue in the following image.

SLIM's next destination, a 600 km circular orbit, is marked in green. From here, all preliminary operations for landing on the moon's surface will be carried out. Once the lander is ready, the beryllonium will be lowered to 15 kilometers (red line), and when SLIM passes this point the lunar landing maneuver will begin.

The whole thing should last 20 minutes, and is expected to take place from 16:00 to 16:20 Italian on January 19. In Japan it will be 00:00 on January 20th.

The main goal of SLIM is to demonstrate a smooth, high-precision landing on the lunar surface. It will use a navigation system based on real-time surface observations, supported by observations of the Japanese satellite SELENE, which has been orbiting the moon since 2007.

Images taken using the navigation camera during, before and after insertion into lunar orbit have been compiled together in a fold-out book. You can see that SLIM is actually moving above the moon's surface.#Moderate build #jaxa #Hazzar pic.twitter.com/nT480PbKCy

– SLIM Small Lunar Landing Demonstration Vehicle (@SLIM_JAXA) December 25, 2023

SLIM carries a multi-band camera (MBC) to evaluate the formation of Xiuli Crater by analyzing the spectra of sunlight reflected from its surface. The goal is to search for the presence of the mineral olivine, which may have been ejected from beneath the moon's surface.

SLIM also carries a pair of small rovers. Lunar Excursion Vehicle 1 (LEV-1) uses a jump mechanism, while LEV-2 is a spherical rover about the size of a baseball. Both are equipped with cameras and scientific instruments.