Overview

The Smart Lander for Investigating Moon (SLIM) mission aims to attempt a ‘pinpoint landing’ on the Moon which is necessary for future lunar and planetary exploration. The lander was launched on 2023-09-07 (JST) and landed on the moon on 2024-01-19 15:20. Then after three overnights, the operation was ended on 2024-08-23.

Lander and Observation Instruments

SLIM

The Smart Lander for Investigating Moon (SLIM) lander, developed by JAXA to achieve a pinpoint landing within a 100-meter ellipse, was launched from the Tanegashima Space Center on September 7, 2023. On January 20 at 00:20 JST, SLIM successfully landed approximately 60 meters from the target site. The designated landing area was located east of Shioli crater (25.2 degrees east, 13.3 degrees south). During the landing sequence, two small rovers, Lunar Excursion Vehicle 1 (LEV-1) and Lunar Excursion Vehicle- 2 (LEV-2) which is also known as SORA-Q, were deployed. After touchdown, ejecta from Shioli crater were observed using the Multi-Band Camera (MBC). The SLIM lander consists of several sub-systems, including a telecommunications system, a power system, and an Attitude and Orbit Control System (AOCS). The telecommunications system includes three S-band antennas. The lander also hosts two navigation cameras (CAM-PX and CAM-MZ), the Multi-Band Camera (MBC), two small rovers (LEV-1 and LEV-2), and a Laser Retro-reflector Array (LRA) provided by NASA.

MBC

The Multi-Band Camera (MBC) is a compact VIS-NIR camera onboard the SLIM lander. The MBC consists of a VIS-NIR imaging sensor, a filter wheel with ten band-pass filters, a telephoto focusable optical system, and a movable mirror for panning and tilting. The sensor is sensitive to wavelengths ranging from 750 to 1650 nm.

The planned landing site is located near Shioli crater (25.2 degrees east, 13.3 degrees south), to the west of Mare Nectaris. Based on observations from the Kaguya (SELENE) spacecraft, there is a high possibility that mantle materials are exposed around Shioli crater. Therefore, we aim to estimate the Mg# (i.e., the atomic ratio of Mg / (Mg + Fe)) of lunar mantle materials, which is crucial for understanding the early history of the Earth-Moon system.

CAM

SLIM has two small navigation cameras for vision-based navigation. One is CAM-PX and the other is CAM-MZ, which have field of views in +X axis and -Z axis of the lander’s frame, respectively.

LRA

LRA (Laser Retroreflector Array) is a small, passive optical instrument designed to provide a target for precision laser ranging from a spacecraft in lunar orbit, enabling geolocation of the lander and its instrument suite and establishing a fiducial marker on the lunar surface. LRA contains eight 1.27-cm-diameter corner cube retroreflectors mounted on a dome-shaped aluminum structure. The LRA unit on SLIM is mounted adjacent to the solar arrays, designed to nominally be facing up from the lunar surface.

LEV-1

Lunar Excursion Vehicle 1 (LEV-1) is a tiny rover developed by JAXA, Tokyo University of Agriculture and Technology, and Chuo University. It’s equipped with a camera and a 3-channel wide range accelerometer. It can explore autonomously based on image, and communicate with the ground stations directly, and also relay communications from the Lunar Excursion Vehicle 2 (LEV-2) to the ground station.

LEV-2 (SORA-Q)

Lunar Excursion Vehicle 2 (LEV-2) is a tiny rover developed by JAXA, TOMY Company, Ltd, Sony Group Corporation, and Doshisha University which has a nickname, SORA-Q. It’s equipped with two visible-range cameras with CMOS detectors and weighs only 228g. It can move on the moon using two wheels.

Achievements

The SLIM mission achieved a successful lunar landing and a demonstration of ‘pinpoint landing’ performance, even though it experienced a trouble of its thruster system for the last minute just before the landing.
The tiny rovers LEV-1 and LEV-2 achieved autonomous, cooperative operation of multiple robots on the moon.