This entry went back into drafts.

Yesterday (Jan 8) around 9:30 UTC I have put an offset of +1.5mm on WE and -1.5mm on NE with a 30 minute ramp. As the lock last night was not very long due to bad weather to confirm the effect of the offset on the optical gain and sensitivity stability.

Figure 1. Last night the offset of +/-3mm on WE/NE for sure increased the coupling of angular control noise. The noise between 20Hz and 40Hz increased between ~19:30 UTC and the unlock at ~22:00 UTC

At 18:14 UTC I have changed the offset ot +2mm on WE and -1mm on NE with a 20min ramp, to check if there is a bit of differential offset that we are putting in, as adding the offsets this morning has put the out-of-loop DIFFp signal based on the 491Hz line in B1 away from zero for TY.

Today (Jan 9) at 07:27 I put +2mm offset on WE with a 30 minute ramp, and no offset on NE. To see if in that case there is less impact on the B1 based DIFFp TY out-of-loop error signal. Last night test did not show much difference, but it was only a 0.5mm change in beam spot on NE.

13:55 UTC Put an offset of +2mm on NE with a 30 minute ramp

17:28 UTC put an offset of -2mm on NE with a 1h ramp