At around 3:30 this morning, the ETMX T240s started to drift to some large values. This morning we were having trouble locking the X arm with green light, and noticed that the REFL CNTRL output was huge, indicating that the cavity length was changing by ~20 um in about 10 seconds. We looked at the ISI screens, saw that the T240 mons were red. After interupting Jeff's Saturday morning errands, we decided to try zeroing the T240s by turning on FM6 (labeled AutoZ) in the T240 X filter banks, when we did this the ISI tripped. It started to Isolate, the outputs of the T240s were still large but not as large as they had been, stage 2 watchdog tripped, then it isolated and the cavity motion is much much less.
The firt attached screen shot shows the green laser control signal roughly calibrated in um, you can see the abrubt change when we tripped the ISI and the much smaller fluctuations after. The second screen shot shows a trend of the outputs over the last two days.
I've looked at this a bit more, but i can't find anything obvious. At ~11:40 UTC, something agitated the ISI and it stayed that way until 21:30 when Sheila tripped the ISI ( T240 time series trend shown in first screenshot) The ETM optic was in a similar state, and returned to normal after the ISI tripped. The ground sensors don't show anything (second plot, reference is from 8:00 UTC, active is from 12:00), and I didn't see any evidence that the ISI isolation loops were ringing (last screen shot, I only show a few, but I looked at them all).
