Amid the accelerating space race, leading space exploration nations strive to develop advanced technologies to enhance landing efficiency on various celestial bodies, aiming for more precise and cost-effective exploration.
Among these efforts, the Japan Aerospace Exploration Agency (JAXA) launched an ambitious project called SLIM (Smart Lander for Investigating Moon), a smart lander designed to test precision landing technologies on the Moon’s surface, paving the way for more complex space missions in the future.
SLIM’s development is part of Japan’s vision to strengthen its lunar exploration capabilities—not only by sending spacecraft but also by improving navigation and autonomous guidance technologies. These advancements allow spacecraft to reach targeted areas with unprecedented accuracy.
While conventional landers rely on low-precision landing systems that may deviate by several kilometers, SLIM aims for a landing accuracy within less than 100 meters of its target, a revolutionary technological feat that could reshape the future of space exploration missions.
This level of landing precision is crucial, especially as interest grows in exploring natural resources on the Moon, such as water ice in permanently shadowed craters. Future spacecraft tasked with mining operations or lunar soil analysis will require highly accurate landing systems to reach these sensitive areas safely.
This is where SLIM’s significance lies—it represents a major leap toward enabling safe landings in rough terrains, allowing scientists to study previously inaccessible environments.
Since Japan has not been a primary player in lunar exploration over past decades, the launch of SLIM serves as a real test of JAXA’s ability to develop technologies that compete with major space agencies like NASA, ESA, and CNSA.
Thus, the importance of this mission goes beyond mere technology testing; it demonstrates the feasibility of new strategies that could reshape how landing and exploration missions are conducted in the coming decades.
However, like any space mission, the challenges and risks were significant. Once SLIM left Earth’s orbit on its journey to the Moon, it became subject to various factors, including orbital corrections, harsh space conditions, and critical moments during landing.
Image-1. SLIM spacecraft LEV modules separation. (Image Credit: JAXA).
While the mission’s core objective was to test new technologies rather than merely achieving a successful landing, any failure at this stage could affect the viability of the technologies Japan aims to develop for future space exploration.
- So, what were the true objectives of SLIM?
- What happened to the spacecraft?
- Did the mission fail?
- And how could this mission impact the future of lunar and planetary exploration?
The True Objectives Behind SLIM
Primary Objective: The Japanese spacecraft Smart Lander for Investigating Moon (SLIM) aims to revolutionize lunar landing technologies by developing and demonstrating a high-precision landing system.
Traditionally, lunar landing zones have spanned several kilometers to tens of kilometers, limiting the ability to select specific scientifically or technically significant landing sites. In contrast, SLIM seeks to achieve a landing accuracy within just 100 meters, a groundbreaking advancement in lunar landing technology.
Key Technologies Enabling These Goals:
Vision-Based Navigation:
SLIM utilizes an advanced technology known as vision-based navigation, enabling the lander to identify lunar surface landmarks using onboard cameras and integrated sensors.
This allows it to determine its precise location during descent. This system is not only used for trajectory correction but also for avoiding hazardous terrain features such as craters and rocky slopes.
Navigation, Guidance, and Control Systems (NGC):
These integrated systems ensure the spacecraft’s stability throughout its journey, from entering lunar orbit to the final landing phase. The system reacts in real-time to navigation data from sensors and cameras, ensuring precise and efficient guidance.
Compact, High-Performance Chemical Propulsion System:
To achieve precision landing, SLIM relies on an innovative small, lightweight chemical propulsion system that provides fine control over speed and direction during descent, minimizing the risk of deviating from the intended landing site.
Weight Reduction Technologies:
SLIM is a prime example of lightweight spacecraft design, incorporating advanced materials and technologies to minimize the weight of essential components such as onboard computers and power supply systems. This not only enhances performance efficiency but also makes the spacecraft more suitable for future missions by reducing launch costs.
These technological advancements align with a broader objective:
Making lunar and planetary exploration missions more frequent and cost-effective. By reducing spacecraft weight and improving landing precision, space agencies can conduct more missions with fewer resources, paving the way for exploring a greater variety of scientifically valuable sites.
Key Components Contributing to SLIM’s Objectives
Propulsion System (RCS):
- Main Engine (OME):
- A 500 Newton bipropellant thruster designed for orbital control and speed adjustments during lunar descent.
- Features a locally developed ceramic combustion chamber, providing an advanced combination of pulsed and broad thrust.
- The lightweight design significantly reduces the overall propulsion system mass.
- 22N Thruster:
- A small 22-Newton bipropellant thruster, consisting of 12 units working together to generate precise directional and rotational forces.
- Enables attitude control, orbital maneuvers, and precision landing.
- Propellant Tank:
- Stores the fuel and oxidizer used by the main engine.
- Lightweight design incorporating a PTFE membrane to minimize mass.
Integrated Control System (ISC):
- Landing Radar:
- A sensor that measures altitude and velocity during descent.
- Utilizes Doppler technology and multiple pulse modes for high-precision altitude measurement.
- Laser Range Finder:
- An optical sensor measuring altitude just before landing.
- Compact and lightweight, enhancing functional accuracy.
- Navigation Camera:
- A small, lightweight camera used during the landing phase.
- Provides compressed images to support navigation and vision-based systems.
Communication System (COM):
- Integrated Computer (SMU):
- Handles all computational tasks for spacecraft control.
- Features high-precision data processing, integrating navigation and vision functions into a single processing unit (MPU).
- S-Band Transmitter (STRX):
- Enables communication between SLIM and the ground station using advanced signal conversion technology.
Power System (EPS):
- Integrated Power Control Unit (IPCU):
- An innovative device managing power distribution and battery charging.
- Thin-Film Solar Cells:
- A lightweight, high-efficiency solar cell design that optimizes power generation while minimizing mass.
- Lithium-Ion Batteries (LICM):
- Provides essential power and withstands vibrations and shocks during launch.
Shock Absorption System (ABS):
- Shock Absorber:
- Equipped with a 3D-printed aluminum mesh structure designed to absorb impact forces during landing.
Payload System (PLD):
- Multispectral Camera (MBC):
- Analyzes the composition of surrounding rocks after landing.
- Lunar Exploration Vehicle (LEV):
- A small rover designed to collect samples and capture surface images.
Image-2. Landing zone and final situation. (Image Credit: JAXA).
Fate of SLIM: Was the Mission a Failure?
The Japan Aerospace Exploration Agency (JAXA) launched the SLIM (Smart Lander for Investigating Moon) spacecraft on September 6, 2023, at 23:42:11 UTC.
It was launched as a shared payload alongside the XRISM mission aboard the Japanese H2A rocket from the Tanegashima Space Center. After successfully separating from the rocket’s upper stage, SLIM embarked on a four-month journey to reach lunar orbit.
On October 4, 2023, at 06:47 UTC, the spacecraft made its first approach to the Moon at an altitude of 5,000 km before entering an elliptical orbit.
After a series of orbital maneuvers, SLIM reached its final orbit around the Moon on December 25, 2023, where its trajectory was gradually adjusted until it stabilized in a polar orbit at 600 × 4,000 km with an orbital period of 6.4 hours.
Over the following month, the spacecraft continued to lower its orbit until it reached 600 × 600 km, then further reduced it to 15 km in preparation for the landing phase.
On January 20, 2024, at 12:00 AM Japan Standard Time (JST) (January 19, 15:00 UTC), SLIM initiated its guided descent toward the lunar surface.
At an altitude of 3.5 km, it relied on its navigation systems to precisely determine its position using onboard cameras, which compared real-time data with reference maps to ensure accurate positioning before transitioning to a vertical descent.
As it neared the surface, the lander activated its hazard detection system to ensure a safe landing away from dangerous terrain.
At 3 meters above the surface, the main thrusters were shut off, leading to a short free fall before touching down on the Moon at 12:20 AM JST (15:20 UTC).
SLIM landed at coordinates 25.2510°E, 13.3160°S, achieving its target of landing within 100 meters of the designated site near Shioli Crater. Despite this unprecedented landing accuracy, SLIM encountered an unexpected issue immediately after touchdown.
Although communication was successfully established after landing, the JAXA team discovered that the spacecraft’s solar panels were unable to charge its batteries.
After analyzing the data, it was determined that one of the thrusters malfunctioned at an altitude of 50 meters, causing the spacecraft to land at an incorrect angle.
As a result, SLIM came to rest with its solar panels facing west, while the Sun was positioned in the east at that time, preventing it from generating the necessary power for continued operations.
With limited battery capacity, SLIM was able to function for only a few hours before its battery charge dropped to 12%, prompting the team to shut it down at 17:57 UTC to conserve energy.
Despite this setback, the spacecraft had already deployed its two small rovers, Lunar Excursion Vehicle (LEV-1) and Lunar Excursion Vehicle (LEV-2), which successfully carried out their missions, exploring the lunar terrain near the landing site.
On January 28, 2024, more than a week after landing, the Sun’s angle shifted, allowing its rays to reach SLIM’s solar panels, which reactivated the spacecraft.
SLIM resumed transmitting new data and conducted short-term operations until the Sun set again, plunging the lander into the long lunar night, which resulted in another communication blackout.
However, SLIM managed to survive the harsh lunar night and was reactivated on February 25, 2024, resuming data transmission.
As the Moon approached another cycle, SLIM entered hibernation again on March 1, 2024, due to the lack of sunlight, but it demonstrated remarkable resilience when it successfully reactivated on March 26, 2024.
During this period, it transmitted valuable images and data about the lunar surface environment, helping researchers study the behavior of electronic systems under extreme lunar conditions.
After surviving three consecutive lunar nights, SLIM continued operating until April 28, 2024, when it transmitted its final data before losing contact permanently.
Following multiple unsuccessful attempts to restore communication, JAXA officially declared the mission’s end on August 23, 2024, confirming that all efforts to reestablish contact had failed, marking the conclusion of SLIM’s historic mission.
Mission Outcome: Success or Failure?
While SLIM’s long-term survival was compromised, the mission was not a failure. It successfully demonstrated precision landing technology, achieved its scientific objectives, and provided valuable data for future missions.
The unexpected landing orientation poses a new challenge for JAXA, but the data collected before loss of contact will aid in improving future spacecraft designs, making SLIM an important milestone in Japan’s lunar exploration efforts.
Image-3: SLIM team. (Image Credit: JAXA).
How Can This Mission Influence the Future of Lunar and Planetary Exploration?
Despite the uncertainty surrounding the fate of the SLIM spacecraft after its launch, the concepts and technologies developed by the Japan Aerospace Exploration Agency (JAXA) for this mission represent a potential turning point in the future of lunar and planetary exploration.
Even if the mission’s success is not entirely clear, the technological advancements achieved will have a significant impact on the design and execution of future space missions.
Enhancing Landing Accuracy and Targeting Difficult Locations :The SLIM mission aims to achieve unprecedented landing precision, with an accuracy of less than 100 meters from the target location, compared to the kilometer-scale accuracy in traditional missions.
This capability allows for the exploration of more challenging lunar regions, such as polar craters, which may contain water resources or terrain of high scientific value.
Advancing Technology for Planetary Exploration:
Even if the mission faced obstacles, the technologies developed—such as vision-based navigation—serve as a foundation for future lunar and planetary missions.
These innovations could be applied to Mars missions, asteroid landings, and explorations of Jupiter’s icy moons, where precise navigation is essential.
Reducing Costs and Enhancing Efficiency :
The focus on lightweight and efficient design in SLIM represents a major step toward lowering the costs of space exploration.
These advancements will help increase the frequency of small spacecraft launches, making deep-space exploration more feasible and cost-effective.
In Conclusion
Despite the challenges and uncertainty surrounding SLIM’s fate, it highlights Japan’s commitment to contributing to space exploration through new and innovative technologies.
Whether the mission fully achieved its objectives or not, SLIM’s legacy will continue to influence future research and developments that will shape the future of space exploration for decades to come.
The SLIM (Smart Lander for Investigating Moon) project represents a bold and pioneering step in the journey of space exploration, not only for Japan but for the global scientific community as a whole.
It is not merely an attempt at precise lunar landing; it is a symbol of humanity’s ambition to explore the unknown, foster innovation, and push the boundaries of scientific knowledge to new horizons.
SLIM’s significance lies in the advanced technologies developed specifically for this mission, such as vision-based navigation and precise guidance and control systems.
These innovations are not just tools for the current mission but a foundation for future transformations in lunar and planetary exploration, reshaping our understanding of how to achieve accurate landings and target challenging, unexplored regions.
Despite the uncertainties surrounding the mission’s outcome, the technical and scientific advancements introduced by SLIM open the door to countless opportunities.
Its technologies could contribute to a sustainable future for lunar resource exploration, the realization of permanent bases on the Moon, and even the expansion of our exploration efforts to other planets like Mars or the icy moons of giant gas planets.
Historically, such space missions have always been a source of inspiration for humanity, reminding us that space remains the vast frontier that we strive toward with ambition and creativity.
SLIM proves that nations, regardless of their geographic size or economic standing, can play a crucial role in shaping the future of space through bold innovation and design.
