The spacecraft successfully completed the deceleration process and activated its descent sequence when it reached an altitude of approximately 100 kilometers (62 miles) above the lunar surface.
The software onboard the spacecraft mistakenly estimated its altitude to be zero when it was actually around 5 kilometers (3 miles) above the ground.
As a result, the spacecraft continued descending at a very slow speed near the surface, thinking it had already landed when it hadn't.
The altitude estimation issue occurred because the spacecraft passed over a large cliff, which was the rim of a crater, during its flight to the landing site.
The onboard sensor recorded an altitude reading of 3 kilometers when it passed over the elevated terrain, which was higher than the estimated altitude value set by the Hakuto-R team.
The spacecraft's software incorrectly identified this reading as abnormal and filtered out subsequent altitude measurements.
ispace had built in the ability to reject abnormal altitude measurements as a safety measure for hardware issues with the sensor, but it backfired in this case.
The simulations of the landing sequence had failed to incorporate the lunar environment on the spacecraft's route, which led to the altitude estimation issue.
ispace made the decision to change Hakuto-R's landing site after the critical design review was completed in 2021.
The spacecraft ultimately went into a free fall and crashed on the moon as its propulsion system ran out of fuel.