Sunday, February 21, 2010

Second Main Engine Firing Stopped Early by Spacecraft

February 19, 2010

The second Apogee Motor Firing (AMF #2) this evening was autonomously aborted after 30 seconds due to high system momentum. The Observatory is safe, the on-board system detected an unexpectedly high momentum, aborted the burn, and returned the Observatory to sun-pointing. Preliminary investigations do not show any indication of a hardware problem, more likely is that the combination of the settling burn (with the ACS thrusters prior to the main engine firing) immediately followed by the initial main engine burn exceeded the limits that were set (i.e. limits were set too low given this particular timing and fuel tank fill conditions). The plan is to continue reviewing the data to confirm the theory. If all holds, the next AMF burn would be scheduled for Sunday evening.