IRAC High Precision Photometry
r48072704 1hrs into the observation ~ 2013-07-08T12:55:21.630'
The jumps in position correspond to wheel speed shifts. Wheel speed shifts are expected due to momentum rebalancing events in the wheel speed controller. The goal of this system is to avoid zero crossing disturbances (which would also induce position disturbances in the data) as long as possible. Autonomous momentum rebalancing only occurs when the system momentum grows above a certain threshold. Once this level is breached, the goal changes to balancing the wheels so that we can stretch out the time until the next desat. If the momentum falls back below that threshold, autonomous momentum rebalancing will once again be disabled.
We see different behavior during the PCS anomaly during the summer of 2013 because that anomaly was not allowing the momentum error integrator to compensate for the bearing drag in the wheels. A shift in wheel speed would introduce a different bearing drag torque, and without the integrator to compensate for this, the shift would not be removed.
These images can be used in analysis as long as the gain associated with the different centroids can be appropriately corrected for.