The Small Lunar Lander for Investigating Moon (SLIM) successfully performed a soft landing on the Moon's surface on January 20, 2024 (JST), marking Japan's first-ever soft landing on the Moon. Its landing performance was evaluated as being within 10 meters or better, marking the world's first successful high-precision landing. By accurately landing near the target landing site, the multi-band camera successfully observed the composition of olivine, which is thought to originate from deep lunar interior. Additionally, the separation of two ultra-small rovers was successfully achieved just before landing. The rovers subsequently photographed the SLIM on the Moon and transmitted this valuable image to us. Furthermore, communication was established with the lander after it had endured three lunar nights, confirming its functionality. This special issue includes 14 papers detailing these achievements. The authors sincerely hope that this special issue will contribute to future mission planning.

Smart Lander for Investigating Moon (SLIM), a small spacecraft with a dry mass of 200kg, was launched on September 7, 2023 by the H-IIA rocket and made a pinpoint Moon landing on January 19, 2024 (UTC). Precise landing performance was evaluated to be approximately 10 meters or less, much better that the target landing accuracy of 100 meters, realizing the world's first pinpoint landing. This paper describes the design and manufacturing results including its compact and lightweight technology, and operational results of the SLIM.

This paper explains the outline of ground segment systems for the operation of Smart Lander for Investigating Moon (SLIM). The ground system consists of seven functional subsystems which are (1) operation planning, (2) tracking, (3) control and operation, (4) orbit determination, (5) data archive and analysis, (6) operation training, and (7) spacecraft ground test. The functions of subsystems have relation to the requests for operations. These subsystems have been integrated by connecting the interfaces between them and testing the conformation to the designs. Various tools involved in each subsystem are introduced. Furthermore, among these tools we focus on some crucial functions for the success of precise landing on gravitational celestial bodies. Additionally, we present the preparation for solving contingencies of both the spacecraft and ground system.

This paper presents a precise powered landing mission design and the results of flight operations for the small lunar lander SLIM. Achieving a successful and accurate landing requires a highly constrained trajectory plan from launch to landing. Additionally, SLIM, being a small spacecraft, must minimize the fuel needed for orbital control, as most of its fuel is used for powered descent and landing. This necessitates energy-efficient transfer using ballistic capture trajectory to lunar orbit with lunar gravity assists. Moreover, the resulting trajectory corrections must be planned efficiently.

The Smart Lander for Investigating Moon (SLIM), developed by the Japan Aerospace Exploration Agency (JAXA), was launched from the Tanegashima Space Center on September 7, 2023 (JST), and successfully achieved Japan's first lunar soft landing and the world's first pinpoint landing on January 20, 2024. SLIM, a 700-kg class small lander launched as a secondary payload with the X-ray Imaging and Spectroscopy Mission (XRISM), represents a shift from landing at easy-to-reach locations to precise landings at desired spots. Achieving high-precision landings on gravitational celestial bodies requires accurate orbit determination and lander control. SLIM utilized sophisticated techniques to enhance its landing precision, including real-time Doppler data modulation removal, onboard optical navigation for orbit determination, and machine learning models to optimize prediction accuracy. Post-landing, the location was confirmed to match images from the Lunar Reconnaissance Orbiter (LRO). This paper discusses SLIM's orbit determination and landing precision improvements and their implications for future lunar exploration.

Smart Lander for Investigating Moon (SLIM) was JAXA's spacecraft designed to demonstrate precision lunar landing technology. SLIM was launched on September 7, 2023 (JST), from the Tanegashima Space Center by H-IIA Rocket No. 47 and achieved a successful pinpoint landing on the Moon on January 20, 2024 (JST). To meet the stringent mass constraints of a small lunar lander, extensive weight reduction was implemented through the development of a lightweight solar array panel (SAP). The SAP incorporated newly developed inverted metamorphic InGaP/GaAs/InGaAs triple-junction (IMM3J) solar cells, featuring an ultra-thin flexible structure of only 13µm with initial efficiency exceeding 32%. These cells achieved more than five times the power-to-mass ratio compared to conventional InGaP/GaAs/Ge triple-junction solar cells, significantly contributing to SLIM's mass reduction goals. The SAP demonstrated exceptional performance throughout the mission, maintaining predicted power output while traversing the harsh radiation environment of the Van Allen belts. This paper describes comprehensive analysis of the SAP's development, on-orbit performance, and operational results, providing valuable insights for future lightweight space power systems.

This paper reports on the operational results of the stainless steel laminated lithium-ion battery cells developed for JAXA's SLIM lunar lander. These innovative batteries were designed to share structural strength between the cell casing and spacecraft structure, achieving high specific energy to support SLIM's goal of a lightweight lunar exploration system. The batteries performed as designed throughout the mission, contributing to Japan's first successful lunar landing. Key operational data is presented, including discharge profiles during launch, the longest eclipse period, maximum discharge rate events, and the lunar descent and landing sequence. The batteries maintained higher than expected state of charge during the descent phase, allowing extended surface operations after landing despite an anomaly in the propulsion system. Post-landing analysis estimated 14% capacity degradation. Overall, the batteries demonstrated reliable performance in the space environment, validating the novel design approach and supporting SLIM's mission objectives.

The Smart Lander for Investigating Moon (SLIM) is a Japanese technology demonstration mission aimed at achieving pinpoint lunar landing and developing lightweight spacecraft systems. The Integrated Power Control Unit (IPCU) in SLIM, utilizing digital control, provides enhanced functionality and reduced weight compared to conventional analog systems. This paper focuses on the IPCU, presenting ground verification activities and in-orbit operational results, along with a discussion on the design of the power controller.

The Small Lunar Landing Demonstration spacecraft, SLIM, planned to land using a new method called the two-step landing. On January 20, 2024 (JST), SLIM successfully achieved a soft landing while maintaining functionality. However, the attitude and speed before touchdown deviated from expectations, leading to the postponement of the two-step landing method demonstration to a future mission. This method is particularly effective for landing on gravitational bodies using elongated spacecraft that fully utilize the rocket's fairing envelope, especially on sloped terrain or for small exploratory spacecraft with strict mass reduction requirements. This paper presents an analysis based on the landing dynamics simulations conducted for SLIM, focusing on factors such as the forces acting on the shock absorbers and the spacecraft during landing, as well as trends in attitude and terrain that contribute to stabilizing the two-step landing.

Japan Aerospace Exploration Agency (JAXA) achieved a significant milestone with its Smart Lander for Investigating Moon (SLIM) on January 19th, 2024 (UT). SLIM succeeded in landing on the moon and achieved overnight three times after landing, contributing to data acquisition for future lunar exploration. This paper reports on the thermal design results and operational results of the SLIM thermal control system.

SLIM is a small lunar lander developed by JAXA/ISAS. It was launched on September 7, 2023 (JST) from Tanegashima Space Center by H-IIA Launch Vehicle and achieved pinpoint lunar landing on January 20, 2024. SLIM was designed to demonstrate pinpoint landing technology and to contribute to future lunar and planetary exploration by developing a lightweight spacecraft system. SLIM propulsion system required not only capability of high Delta-V and enough thrust for orbit transfer and lunar landing, but also high controllability of thrusters required for pinpoint landings, as well as a stronger weight reduction than that of conventional spacecraft. To achieve these requirements, we constructed and operated a unique propulsion system that has never been seen on a conventional spacecraft, including a bipropellant propulsion system with a blowdown system, pulse injection operation using 500 N-class thrusters, adoption of a shape memory alloy valve, and a newly developed integrated fuel/oxidizer tank. This paper describes the development and operational results of SLIM propulsion system in detail.

This paper discusses the landing and descent sequence design applied to the Smart Lander for Investigating Moon (SLIM) mission that achieved a pinpoint lunar landing in January 2024. The main outcome of the SLIM landing and descent sequence design is the derivation of an elaborate landing and descent reference trajectory to achieve the SLIM mission objective of a pinpoint lunar landing. The landing and descent reference trajectory is derived by solving an optimal control problem that considers a variety of environmental conditions, including the orbital sequence from launch, vision-based navigation, obstacle avoidance, characteristics of navigation sensors, high-precision guidance laws, translational and rotational control performance, propellant consumption, propulsion system conditions, and lunar surface conditions for landing. The derived results are reflected in the parameters of the landing and descent sequences and the guidance laws. The SLIM landing and descent sequence design applies the framework of multi-disciplinary system design optimization, a design method in which the entire system is mathematically modeled as a set of interacting subsystems and optimized in an integrated manner. This framework enables the design of efficient landing and descent sequences even when mission conditions change. This paper presents the results of the landing and descent sequence design applied to actual SLIM mission operations. It also presents several landing and descent sequence design examples studied to prepare for changes in mission conditions.

The Smart Lander for Investigating Moon (SLIM) lander made a pinpoint Moon landing in January 2024. Its key technologies were a vision-based navigation and autonomous guidance, navigation, and control (GN&C). This paper focuses on autonomous GN&C for the SLIM's pinpoint landing. The onboard GN&C algorithm can correct a large initial state dispersion for a pinpoint Moon landing, in addition to considering thrust pointing constraint and subsurface flight avoidance for its terminal descent. The developed GN&C architecture successfully orchestrated the lander effectively to achieve the soft pinpoint Moon landing.

SLIM was developed by JAXA/ISAS and demonstrated a pinpoint landing on the Moon on January 20, 2024 (JST). SLIM employs vision-based navigation (VBN), a terrain relative navigation method using an optical camera, and VBN was performed a total of 14 times in seven areas during lunar landing operations. The vision-based navigation system has onboard reference crater maps. The crater maps were created based on high-resolution topographic data obtained by multiple lunar orbit satellites. This paper describes the selection of the crater map area, the method of creating the terrain digital elevation model and reflectance map, the evaluation of crater reproducibility by comparison with orbiting satellite images, and the results of comparison with actual images obtained in lunar landing operations.

The Multi-Band Camera (MBC) on board the Smart Lander for Investigating Moon (SLIM) was designed for high-resolution near-infrared imaging of lunar rocks, achieving a spatial resolution of 1.1mm per pixel from a distance of 10 meters. A standout feature of MBC is its capacity to estimate the olivine Mg♯ (Mg/(Mg+Fe)) using 10 band-pass filters covering wavelengths from 750 to 1650nm. The instrument incorporates an auto-focus system, a movable mirror mechanism, and a specialized spectral observation framework, representing a substantial advancement in lunar surface exploration. Despite the unanticipated landing attitude of SLIM, MBC successfully performed numerous scans, acquiring near-infrared images with unprecedented spatial resolution. These observations represent a significant breakthrough in lunar exploration technology, marking a major advancement in surface analysis capabilities. The techniques and knowledge gained will serve as valuable resources for future endeavors, such as the forthcoming LUPEX mission.