Around 22.00 UTC, the operator called me because the DMS flag for TCS_WI_CO2_PWROUT became red.

Once connected, I noticed that the related signal fell down, below the threshold, because of a change in the WI main CO2 laser state: see all WI CO2 related channels in Fig. 1.

I recovered the correct value of the power injected inside the ITF with the WI DAS outer ring (see TCS_WI_CO2_POWER_CH_PICKOFF channel) by rotating the relative waveplate (ending around 22.20 UTC), to restore the ITF thermal compensation condition for locking. 

The flag related to the channel TCS_WI_CO2_PWROUT would remain red: I’ve asked the operator to temporarily shelve it; the WI CO2 main laser condition should be checked again tomorrow morning.