Jennie, Jenne, Sheila, Keita

While the PSL team were preparing for a PSL in cursion, I started moving MC3 based on our plan to re-align onto the ISS array and IM4 TRANS QPD after the PMC swap last week.

We tried going up in yaw, saw some increase in power on IM4 trans QPD but then the ISS second loop QPD started to become further from the centre position as did the IM4_TRANS QPD (this is well centred enough that we could see the power drop whereas the ISS QPD started quite far off centre so that the nsum is quite close to zero).

We went back to the maximum value then tried IM3 alignment is both DOFs but this did not improve things in both QPDs so we tried MC3 pitch. Sheila then noticed that we were mazking the IMC relflected spot some horrible higher order mode so we decided to stop and think.

MC1 and MC3 changed in common yaw due to the WFS as we changed the uncorntolled differential DOF (MC1 - MC3), which we did not expect, to recover our alignment we would need MC1 and MC3 to change differentially as they did after the PMC swap, in this image.

The ndscope channels I used for this alignment walking session are attached with cusors before we changed anything and after we recovered the IMC alignment to pre-maintenance.

In conclusion we have reverted the IMC alignment back to before our changes as we think some action before the in-vacuum mirrors is needed.

Plan: To revert periscope PZT and MC1 back to their positions before the PMC swap and get Jason/Ryan to move steering mirrors in the PCAL enclosure to recover the prompt reflection from the IMC as witnessed by the MC WFS behind MC1. Then we can re-align the IMC.