Looking at some of the LSC demodulated signals, I found that the RF phases changed by some noticable amount. I then found that the CO2 laser on ITMX had been tripped at 13:51 local (or 21:51 UTC) today. I went to the rack at the floor and saw that a red indicator for 'TEMP' was on at the front panel. Power cycling the unit with the key untripped it. I pressed the red button for opening the gate and confirmed that the laser power was back to the nominal of 210-ish mW in the medm screen. The attached is a one day trend of the laser power, calibrated into the power at ITMX.

I did not do any deep investigations at this point.