On January 20, 1994, at 1443 UT, the momentum wheel control circuitry of the Intelsat K spacecraft at geostationary orbit suffered an operational anomaly causing a loss of attitude control. The system was switched to the backup circuitry, and control was reestablished. The same day, at 1735 UT, the Anik E-l spacecraft, also at geostationary orbit, suffered the same kind of operational anomaly in the momentum wheel control circuitry [Rostoker, 1994].
According to newspaper accounts the next day, Telesat Canada operators struggled for 8 hours to regain control of the Anik E-1 satellite. They were able to finally switch to the backup momentum wheel controller and resume reasonably normal operations.