Details of the first touchdown rehearsal

The mission posted a schedule here before the descent operation began. Descent from home position began at 06:25 on 11 September. This, and all other times in this update, are UTC. One thing I am unsure about is whether the reported times are spacecraft event time or Earth received time; one-way light time was about 17.4 minutes.

Updates on Twitter indicated that they’d reached 12 kilometers at 11:50 and 10 kilometers at 13:20. The spacecraft paused as planned below 5 kilometers (a position they refer to as “Gate2”) in order to await approval from the mission controllers to proceed. The team gave approval at 15:32. The spacecraft had reached 2.5 kilometers at 22:50 and 1.5 kilometers at 01:40 on 12 September.

Unfortunately, the operation halted shortly after that. The Hayabusa2 twitter reported: “Hayabusa2 is now rising after stopping its descent. Spacecraft status is normal. At an altitude of about 600m, descent was autonomously stopped, likely due to the distance measurement by the laser altimeter (LIDAR) becoming impossible due to the low reflectance of Ryugu.” And: “The spacecraft is now returning to the home position (about 20km from the centre of Ryugu). From tomorrow, we will revise the descent procedure, including reviewing the LIDAR settings.”

The original plan had Hayabusa2 attempting deployment of the first pair of MINERVA-II microrovers on 20 to 21 September. The mission hasn’t stated yet whether they’re going to proceed for that attempt as planned, or if they will now need to do another touchdown rehearsal. Stay tuned to the Hayabusa2 website and Twitter feed for news!