Executive summary: H1 returned to observing as of 19:35 UTC after a challenging week.

Following my lock acquisition and troubleshooting attempts this morning, H1 was able to relock fairly easily again all the way up to LOWNOISE_LENGTH_CONTROL. I requested LOWNOISE_ASC and began watching carefully for any rise in the ~9.8 Hz bounce mode, which I saw quickly start to come up in the early seconds of LOWNOISE_ASC. Once the state finished, my first reaction to try and stop this increase was to transition back to high-gain ASC, which I did using the script on the ISI config screen. Looking back in the ISC_LOCK Guardian log, I was reminded that right before LOWNOISE_ASC we had gone through DAMP_BOUNCE_ROLL, which I assumed was not really doing anything since the roll mode damping gain was commented out. However, I saw that in this state, an entry in the LSC output matrix was being set to -1, which I traced down to being the entry for sending DARM control to ETMY, meaning we likely have been unintentionally exciting the ETMY bounce mode. After confirming that this was very much incorrect, I set the matrix value back to 0 and almost immediately saw the 9.8 Hz peak and the bounce mode monitors start to drop. After a few minutes of watching things calm down, I transitioned back to lownoise ASC and saw no sign of the mysterious hump around 60 Hz that had been seen yesterday. With things looking good so far, I requested NOMINAL_LOW_NOISE, which H1 made it to without issue.

It appears the line in the DAMP_BOUNCE_ROLL state code to send DARM control to ETMY has been there for some time, and a comment there says it's to allow for roll damping on ETMY, which would use DARM as the error signal, so this makes some sense. Before yesterday, this state was being run right before we power up from 2W, and a later state would correct the LSC matrix settings so that no erroneous actuation was being sent to ETMY. To remedy this, I have commented out the line that sets the LSC matrix from DAMP_BOUNCE_ROLL. The roll damping we have been using is still commented out as well, so this state essentially does nothing right now and remains between LOWNOISE_LENGTH_CONTROL and LOWNOISE_ASC.

Soon after reaching NLN, I noticed the familiar 1 Hz ASC oscillation was starting to ring up, seen mostly in CSOFT_P and INP1_P.  At Elenna's direction, I increased the CSOFT_P gain from 20 to 25, and the oscillation started to turn around and subside after a few minutes. Elenna has updated ISC_LOCK to set the final gain of CSOFT_P to 25, and commented out the 30 minute reduction of the gain in the THERMALIZATION node.

Elenna and I then tackled the outstanding SDF diffs, which all ended up being accepted, and are documented in the attached screenshot.

Since squeezing looked like it could have been improved, I ran SQZ_MANAGER through 'SCAN_SQZANG_FDS', which noticeably improved DARM at high frequency.

With things looking about as wrapped up as they could be, I set H1 to start observing for the first time in a few days at 19:35 UTC.