FLASH REPORT: Zero Gyro Software Sunpoint entry
At 243/23:01:54 UTC Gyro 2 disparity counts exceeded limits during an LOS period and HST entered Zero Gyro Software Sun Point. The vehicle was in M2G mode in orbit night with a vehicle slew in progress when this occurred. Gyro 2's motor current and digital data were zero after telemetry was reestablished.
On Saturday, September 1st at 9am EST a Zero Gyro Entry (Gyro 2 failure) Status Briefing was held with the Mission Operations Team, Science Institute and HST Project. Status of each subsystem was provided. PCS confirmed Gyro 2 failure and that Gyro 6 was powered on at 244/0554 GMT. Other subsystems are performing nominally and as expected. TCS did change yellow limits on the OTA Baffle temperature to the SM limits (w/AD closed). EPS reported a change in the structure current profile following the anomaly. An Ops Note was issued to increase structure current ground limits by 0.4 amps (5.4 to 5.8A). There was an increase of up to 1.5 amps in the structure current profile which EPS is monitoring.
HSTARS: 10983 Loss of Lock - Without Acquisition Failure @ 247/2041z GSAcq (1,2,1) at 247/19:45z was successful. At 247/20:13:57z began flagging in and out of Gyro Control (RGA Only / FGS/RGA). Additionally, Mnemonics FSUBLOL, FGSLOL, FGS_STAT began flagging in and out indicating a possible Loss of Lock. At 247/20:41:56z TERM EXP as scheduled. During this time FGS's maintained SCI INIT / LATCH on acquisition.