The HGA has a narrow beam width which needs to be accurately pointed towards the earth. A significant, unplanned roll excursion causes the HGA to be mispointed, with loss of signal as a result. The ESR mode was triggered to ensure low rate telemetry through the low gain antenna which has a much wider beam. Fuel consumption for today is estimated to be around 800 grams. The spacecraft will be returned to Normal Mode at the end of the day, and instrument recovery operations are scheduled for tomorrow and Friday.
Instruments are in safe configuration and appear to be unscathed from the episode.
Spacecraft recovery is proceeding with maneuvers to compensate for a stay of about 21 hours in ESR mode, which has perturbed the angular momentum, orbit and roll of the spacecraft. Instrument recovery operations will take place after SOHO returns to Normal Mode. Three-axis attitude control is accomplished via thrusters and the ground system is required to provide roll axis control. ESR recovery procedures were initiated to retrieve data for analysis and allow open-loop roll control. Roll rate adjustment commands were successfully uplinked and the gyroless ACU flight software patch was successfully reloaded to ACU A in an inactive mode.