SLIM
SLIM demonstrated high-precision lunar landing technology near Shioli crater.
The mission in three questions
- Can terrain-relative vision reduce lunar landing error from kilometres to the scale of hundreds of metres?
- What happens operationally when precision targeting succeeds but final landing attitude is abnormal?
- How can very small deployable vehicles contribute to surface mission architecture?
Mission purpose and context
JAXA's SLIM mission tested whether a lunar lander could target a small scientifically selected site instead of accepting the broad landing ellipses typical of earlier missions. Precision landing was the primary technology objective.
Spacecraft and mission architecture
SLIM used image-based navigation and terrain matching during descent to target an area near Shioli crater. It also carried a small science camera and deployed two miniature lunar excursion vehicles shortly before touchdown.
Payload and measurement highlights
- A vision-based navigation system compared surface imagery with onboard maps to improve landing accuracy.
- The Multi-Band Camera was designed to examine local rock composition.
- Small deployable LEV-1 and LEV-2 vehicles demonstrated novel surface mobility and imaging concepts.
Flight and surface operations
SLIM landed in January 2024 within roughly 55 metres of its target, meeting JAXA's precision-landing objective. An unexpected spacecraft attitude left its solar panels poorly illuminated, but changing Sun angles later restored power and enabled several operational periods beyond the initial landing phase.
Mission sequence
- 6 September 2023: launched with Japan's XRISM observatory.
- Entered lunar orbit in December and attempted a precision landing on 20 January 2024 Japan time.
- The spacecraft landed close to its target but in an unexpected attitude; intermittent operations resumed when illumination conditions supplied solar power.
Science and measurements
The Multi-Band Camera examined rocks around the landing site to investigate their composition and geological context. The mission's principal scientific value, however, was tied to demonstrating access to tightly constrained terrain.
What changed because of this mission
SLIM showed that autonomous image navigation can dramatically reduce lunar landing dispersion. That capability matters when future missions need to reach small geological exposures, resource targets or infrastructure zones rather than broad safe plains.
Mission outcome
Its landing approach targeted a much smaller error ellipse than conventional lunar landers, advancing precision landing capability for scientifically constrained sites.
The outcome should be read against the mission's actual objectives and architecture. Multi-element missions can have different results for an orbiter, lander, rover or sample-return stage, while a shortened mission can still return important science or demonstrate a critical technology.
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Primary reference
JAXA - SLIM. SLIM precision landing mission.