ITF found locked in LOW_NOISE_3 with SCIENCE mode (Autoscience ON); BNS Range ~54 Mpc. Violin modes excited after last relock due to earthquake (DMS plot in fig.1). Unlocks (times in UTC):
02:38 - from LN3 due to PR_TX missing data? (pdf 1). 02:58 - from CARM_NULL_1F with a long series of IMC unlocks for the next handful of minutes. 03:40 - from ACQUIRE_LOW_NOISE_3. 03:44 - from LOCKING_ARMS_IR.
ITF relocked at 04:31UTC, back in SCIENCE at 04:34UTC. Unlocked again at 04:55UTC due to diverging SSFS correction(? pdf 2) relock in progress.
The unlock at 04:55:31 UTC, as long as the ones at 03:40:02 and 02:39:17 are most likely due to a pathological behavior of the ML that we still need to understand. They are the same as the one reported in #67675.
We can observe EOM and PZT corrections increasing a few minutes before the unlock (fig.1) and the error signal oscillating at 60kHz just before the unlock (fig 2.)
Looking at one of those unlocks (03:40:02 of the October 1st), the origin isn't clear yet.
In the plot here we can see that the unlock happens after a jump on the IMC REFL PRE:
However, the EOM CORR and the othere signals were already into the pathological condition of "sawtooth" behaviour highlighted by Camilla and visible already few minutes before the unlock:
Zooming in time (fig. 4-6) we can see that the behavior starts in the EOM, and maybe directly into the ML itself, before the other parts could see something relevant:
