Japan’s SLIM Moon Lander Lands Upside-Down, But Tiny Rover Saves the Mission
In a dramatic turn for Japan's first lunar landing, the Smart Lander for Investigating Moon (SLIM) touched down on the lunar surface on January 19, 2024—but ended up inverted. The awkward orientation prevented its solar panels from generating adequate power, threatening the mission’s objectives.
However, the story didn’t end there. A tiny, spherical rover named LEV-2 (also called SORA-Q) was deployed from the lander and operated for roughly 100 minutes, capturing critical images of the stricken lander and its surroundings, which were relayed to Earth via the LEV-1 communications rover.
The Rover’s Design and Performance
A paper published in Science Robotics on June 10, 2025, authored by Daichi Hirano of JAXA, details the rover’s innovative design and its performance under challenging conditions.
- Autonomous Navigation: LEV-2 demonstrated autonomous navigation, morphable mobility, and onboard image processing to traverse the rugged lunar terrain.
- Operating Window: The rover functioned for approximately 100 minutes before communication was lost.
Key technical weaknesses were also identified. The post-mission analysis highlighted several areas for improvement:
- Telemetry Gaps: The telemetry recording interval of 32 seconds was too infrequent.
- Communication Dropouts: Significant dropouts occurred in the link between LEV-2 and the LEV-1 relay rover.
- Software Limits: The rover’s software needed a larger number of preloaded states and transitions to handle unexpected scenarios more robustly.
Mission Context & Legacy
Despite the landing orientation issue, SLIM survived three lunar nights (each roughly two weeks long) before finally ceasing communication in late August 2024.
The successful deployment and operation of LEV-2 is considered a major proof of concept for small, distributed robotic systems in future planetary exploration. It transformed what could have been a total loss into a significant data-gathering success.
- National Milestone: SLIM made Japan the fifth nation to achieve a soft landing on the Moon.
- Critical Data: The rover’s images allowed engineers to assess the landing outcome and provided crucial supplementary data about the lander’s inverted state.
The LEV-2 rover successfully imaged the lander in its inverted state and provided critical supplementary data.
The mission underscores the value of deploying multiple, smaller robotic assets to create redundancy and gather richer scientific data, even when the primary lander faces severe difficulties.