The first operation rehearsal for the first touchdown of Hayabusa2 began on September 10 and during September 11, the spacecraft descended towards Ryugu. Today (September 12), the spacecraft was approaching the planned lowest altitude in the descent when the spacecraft autonomously stopped descending at about 600 m, and started to rise. The cause was that the laser altimeter (LIDAR) became unable to measure the distance between the spacecraft and surface of the asteroid. LIDAR measures distance by reflecting a laser from the asteroid surface. A probable reason for this measurement becoming impossible is the low reflectance of the surface of Ryugu.
The condition of the spacecraft is normal and is today returning to the home position (about 20 km from the asteroid center). From tomorrow, we plan to revise the descent procedure, including a review of the LIDAR settings.