ISS CMG2 is Offline

Editor’s note: ISS CMG 2 (Control Moment Gyroscope), one of three aboard the ISS, is off-line because a RPCM (Remote Power Controller Module) opened, thus removing power to the CMG. This is the same RPCM that was installed last year during an EVA to replace another RPCM which had failed, also taking CMG 2 offline.

NASA Space Station On-Orbit Status 16 March 2005

“Early this morning, the external Remote Power Controller switch #17 (RPC-17) tripped open, shutting down CMG-2 (control moment gyroscope #2). Automatic software reconfigured the steering law for the two remaining gyros, CMG-3 & CMG-4. Assessment of the anomaly is underway. [After a similar “Failed Open” trip of RPC-17 on 4/21/2004, CMG-3 & CMG-4 performed nominally for two months, with the Russian ACS (attitude control system) thrusters ready to take over at any moment, until the power switch was replaced on 6/30/04 by Padalka and Fincke on EVA-9B.]”