Jennie W, Sheila, Gabriele remotely

Summary:  With the ISS second loop open, we were able to move the IMs without loosing lock.  We realized that the BS camera set point is not ideal for power recycling gain, and that is the reason that the IM moves seemed to improve build ups.  After reseting the camera servo set point, we were able to increase power on the ISS array and IM4 by moving IM1 yaw in the opposite direction from past moves ( 76534 and 76607 ). 

Details:

We moved IM1 and 3 with the ISS second loop open (take IMC_LOCK to LOCKED), this allowed us to move the input pointing without loosing lock. 

We believe that the improvements in build ups seen in 76534 and 76607 were due to the spot on the ITMs/BS moving. When Jennie moved the IMs in the same direction as these earlier attempts, the build ups increased in both arms and LSC POP, but once the CAM1 YAW servo converged the build ups where back to where they started (screenshot).  The IM move also decreased the power on the ISS second loop array (in and out of loop sums) and IM4 trans QPD dropped, indicating that this move may have been the wrong direction to reduce any clipping in HAM2.  We then moved the CAM1 YAW set point to where the error signal was at the maximum build up time, and this restored the build ups.  

Jennie moved the IMs back to their starting place, which restored the power on IM4 trans and the ISS array, then we walked the CAM1 YAW offset (BS camera feeds back to PRM) to maximize the POP and arm powers, we found that an offset of -236 counts seemed best.   This is consistent with what Jennie and Camilla found with the stepper scripts in 76770.  In 76695, Camilla looked at how the camera offsets change from lock to lock, when they are set after ADS converges. This gave us a roughly 0.5% more power in the arms. We want to change the guardian to use this set point in every lock, and retune the ITMs A2L gain for this new set point, but we haven't done that today.

Next Jennie moved IM1 yaw in the positive direction, which increased the power on IM4 trans and ISS second loop array PDs screenshot and here.  While she was doing this the sqz team was injecting anti-sqz, but when they were done we had a quick quite time for a DARM comparison, it appears that we might have made the noise worse.  We wll double check as we revert this move after the squeezers are finished.