Japan’s SLIM successfully enters lunar orbit, gears up for precision moon landing
HELSINKI — Japan’s SLIM robotic spacecraft has entered lunar orbit, marking a significant milestone in its mission to achieve a precision moon landing. The Japan Aerospace Exploration Agency (JAXA) announced on Christmas Day that SLIM completed a successful lunar orbit insertion burn, positioning itself for a landing attempt scheduled for January 19.
SLIM is now in a polar lunar orbit measuring 600 x 4,000 kilometers, as planned. JAXA confirmed that the spacecraft is operating normally and will soon begin the process of gradually lowering its orbit in preparation for the upcoming landing.
The scheduled landing is set to take place on January 19 at 10:00 a.m. Eastern Time, with the spacecraft expected to touch down approximately 20 minutes later. The aim is for SLIM to land within 100 meters of its target point on the sloped rim of the mid-latitude Shioli crater.
The journey towards lunar orbit began on September 6 when SLIM was launched alongside the XRISM space telescope on a H-2A rocket from Japan’s Tanegashima Space Center. Following its launch, SLIM entered a low Earth orbit and underwent a series of orbit-raising maneuvers in order to navigate to the moon.
After a translunar injection burn on September 30, SLIM conducted a lunar flyby on October 4, which set the spacecraft on its propellant-saving trajectory towards the moon. This ultimately led to the successful lunar orbit insertion on Christmas Day.
According to JAXA, SLIM’s next step will be to gradually lower its farthest point from the moon, known as apolune, until it reaches a circular orbit at an altitude of approximately 600 kilometers by mid-January. The spacecraft will then continue to decrease its orbit, reaching a perilune altitude of 15 kilometers on January 19, as it prepares for the landing. At this point, SLIM will decelerate from a speed of around 1,700 meters per second.
To ensure a safe landing, SLIM is equipped with five crushable, 3D-printed aluminum lattice landing legs that will absorb the impact of touch down on the sloped rim of the Shioli crater, measuring 300 meters in diameter.
If the mission is successful, Japan will become the fifth country to achieve a soft landing on the moon. India accomplished this milestone in August with its Chandrayaan-3 mission.
The main objective of SLIM is to demonstrate a highly-accurate lunar soft-landing using a lightweight architecture. It employs a vision-based navigation system and carries observational data from Japan’s SELENE orbiter, which was launched in 2007. This system will play a crucial role in identifying the landing zone during SLIM’s autonomous descent and landing. Additionally, a laser range finder will assist in the final stages of descent.
Beyond the landing itself, SLIM is designed to conduct experiments on the lunar surface during the remainder of the lunar day. It is equipped with a Multi-Band Camera (MBC) that will analyze the composition of the Shioli crater by studying the spectra of sunlight reflected from its surface. One of the key objectives is to identify the presence of olivine, a mineral that may have originated from beneath the moon’s crust.
SLIM is accompanied by two small, innovative rovers. Lunar Excursion Vehicle 1 (LEV-1) utilizes a hopping mechanism, while LEV-2 is a baseball-sized, spherical rover. Both rovers are equipped with cameras and science payloads.
JAXA believes that the mission’s success could lead to cost-effective exploration efforts in the future. The ability to land with high accuracy will facilitate access to scientifically significant areas instead of relying solely on safer landing zones.
With a dry mass of 200 kilograms and a wet mass of 700-730 kilograms at launch, SLIM had an expected development cost of 18 billion yen ($120 million).
As Japan’s SLIM spacecraft prepares for its historic landing on the moon, the world eagerly awaits the outcome of this ambitious mission, which could have far-reaching implications for lunar exploration and our understanding of Earth’s nearest neighbor.
