Today we added an output to OM3 from the ASC model, and recalculated the DC centering control in HAM6 so that three degrees of freedom are controlled by the three tip-tilt actuators.  The DOFs we chose to control are two from the OMC (POS and ANG) and the spot position on AS_A.  Initially we went with AS_B, but this scheme led to a worrisome amount of beam jitter on AS_A and we decided to switch.

The AS_A spot position is controlled through the DC3 filter bank in the ASC model.  The 3x3 control matrix for {DC3, POS, ANG} --> {OM1, OM2, OM3} was calculated using a measurement of the sensing matrix from last September.  (This was done for both pitch and yaw, of course.)  The loop gains are set very roughly to generate only a modest impulse when the input switches are turned on.  We'll measure these loops using a single bounce later this week.

The Guardian has been updated to use this new topology.  The OMC QPDs loops are now enabled as part of the AS DC centering shortly after DRMI lock acquisition.  Note that all three loops need to be closed to maintain the correct spot position on AS_B!

With this new centering we've turned on all the ASC loops while on resonance and things seem ok.  Since we're not directly controlling the spot position on the WFS that is used for MICH and SRC1 we should check that unsuppressed beam jitter doesn't couple into those error signals.

Attached is a screenshot that records the control matrices.  Note that we're only using DC3, not DC4, in the ASC output matrices.