The Japan Aerospace Exploration Agency (JAXA) would like to provide the latest information about the status of the Optical Inter-orbit Communications Engineering Test Satellite "Kirari" (OICETS) after one of the four onboard reaction wheels(*) was disconnected from the attitude control system at 12:13 p.m. on November 24, 2005 (Japan Standard Time, JST.)
The "Kirari" is designed to be a redundant structure which enables the satellite to control its attitude with the remaining three reaction wheels even though one of them is disconnected; therefore, it has successfully been carrying out a series of optical communication experiments.
In parallel with the implementation of missions, JAXA has been studying the cause of the disconnection. As a result, it is currently estimated that the safety function of the attitude control system disconnected the reaction wheel because its error monitor for the number of revolution indicated an abnormal value.
Based on this investigation result, JAXA started to send a command to reactivate the disconnected reaction wheel from the Masuda Tracking and Communication Station at 1:44 a.m. on April 20 (Thu) (JST), and confirmed that no problem arose in the wheel drive unit as well as the wheel itself. At 2:13 a.m. on April 21 (Fri) (JST), the disconnected reaction wheel was reintegrated into the attitude control system by a command from the Perth ground station. The satellite is now shifted to the attitude control mode with four attitude control reaction wheels. The "Kirari" is now in a stable condition.
* Reaction Wheel:
Equipment that controls the attitude of a satellite through the reaction of the torque generated by changing the number of revolution of a rotating disc (fly wheel) by a motor.
