Attitude control
JAXA ceased efforts to recover the satellite on 28 April 2016, switching focus to anomaly investigation. It was determined that the chain of events that led to the spacecraft's loss began with its inertial reference unit (IRU) reporting a rotation of 21.7° per hour at 19:10 UTC on 25 March 2016, though the vehicle was actually stable. The attitude control system attempted to use "Hitomi" reaction wheels to counteract the non-existent spin, which caused the spacecraft to rotate in the opposite direction. Because the IRU continued to report faulty data, the reaction wheels began to accumulate excessive momentum, tripping the spacecraft's computer into taking the vehicle into "safe hold" mode. Attitude control then tried to use its thrusters to stabilise the spacecraft; the Sun sensor was unable to lock on to the Sun's position, and continued thruster firings caused "Hitomi" to rotate even faster due to an incorrect software setting. Because of this excessive rotation rate, early on 26 March 2016 several parts of the spacecraft broke away, likely including both solar arrays and the extended optical bench.