SB SAT @ AMSAT $ANS-358.01 UOSAT-2 (UO-11) Y MAGNETORQUER FAILURE HR AMSAT NEWS SERVICE BULLETIN 358.01 FROM AMSAT HQ SILVER SPRING, MD, DECEMBER 22, 1996 TO ALL RADIO AMATEURS BT BID: $ANS-358.01 It was recently observed that UoSAT-2 (UO-11) spin period was non-nominal. Ground controllers at the UoSAT control station in Surrey manually checked the magnetorquers that are used to control the spacecraft attitude. Both the X and Z torquers were found to be operating correctly, however the Y torquer appears to have failed. The Y torquer is used for maintaining the spacecraft spin period at approximately 5 minutes per revolution and this failure will therefore prevent the OBC from controlling the spacecraft spin rate. During the afternoon passes over the UoSAT control station on the 22nd December, new flight software was uploaded to the OBC that uses the X magnetorquer for spin control instead of the Y magnetorquer. Ground controllers at Surrey will continue to monitor the spacecraft attitude over the next few days to ensure that the updated software has cured the problem. The magnetorquer on UoSAT-2 is controlled by a relay and when the torquer is commanded on, only a small increase in current is observed. It is assumed that this current is the relay coil operating so the probable failure mode is that the relay contacts have failed or the magnetorquer coil has become open circuit. UoSAT-2 was launched from Vandenburg Air Force Base in the United States in March 1984 and has operated successfully for over 12 years completing over 68000 orbits of the Earth. [ANS thanks Chris Jackson , G7UPN / ZL2TPO ,Groundstation and Operations Manager Surrey Satellite Technology Ltd for this update.] /EX