I looked into the recent change in H1 behavior, with H1:LSC-POP_A_LF_OUT dropping, and causing lock loss, and see alignment changes that could be contributing to this issue.

The shifting IMs in HAM2 cannot account for alignment changes in the 150 day trend, so there is something else at work here.

Changes in yaw over 150 days:

• IM1 yaw -6urad
• IM2 yaw +10urad
• IM3 yaw -26urad (drift minus one big jump that was an intentional move of the optic)
• PRM yaw +5urad
• PR2 yaw +51urad

Changes in pitch, comparing PRM to PR2 (different chambers)

• PRM pitch +5urad
• PR2 pitch +8urad

The change in PR2 yaw of +51urad is significantly larger than the changes in the PRM pitch and yaw, and PR2 pitch.

The changes in PR2 yaw may be a response to the cumulative effects of the smaller changes seen in IM1, IM2, and IM3.

Changes in IM pitch:

• IM1 pitch -5urad
• IM2 pitch unknown due to multiple jumps
• IM3 pitch 0urad beginning to end, but varied +/-10urad over the 150 days

The change is IM3 yaw of -26urad is significant;y larger than the changes in pitch or yaw in IM1, IM2, and IM3.