H1 out of Observe at 01:16:37UTC:

• H1:LSC-POP_A_LF_OUT dropped and attempts to save the lock with alignment of IM2 and PR2 in yaw were unsuccessful
• My theory is that the cumulate drifts in IM1-3 yaw have moved the beam on PR2 and the +51urad change in PR2's yaw alignment are in part due this beam shift.
• IM2 yaw alignment offset was changed from 3428 to 3437, a total of 9urad, however I realize now that that added to IM2's overall O1 change.
• PR2 yaw alignment offset was changed from 4313 to 4316, a total of +3 urad.

Lockloss at 01:35:56UTC:

• There was 4 minutes before lockloss where POP_A_LF was increasing, so I kept the alignment changes and relocked
• a couple time H1 reached Low Noise and lost lock due to the earthquake
• when H1 returned to Low Noise a third time, POP_A_LF stabilized at 16100 and has stayed there for the entire lock of 3.5 hours.
• this lock is better, so moving PR2 "higher" in yaw values (slider and M3 OSEM readings) improved POP_A_LF
• should this hold, in future alignments it would be beneficial to move PR2 higher in yaw if possible, and certainly avoid moving it  to "lower" yaw values

Summary:

• PR2 + direction in yaw is good for POP_A_LF stability, at least tonight