Took over from Nutsinee. Dan, Kiwamu and Darkhan also here. 07:15 UTC Lock loss. SUS OMC SW WD tripped. Possible earthquake. 07:21 UTC Touched up SUS ETMX pitch for locking on green. X arm green power remaining around .8 07:26 UTC Requested INIT, DOWN then NOMINAL_LOW_NOISE. Did not help. 07:39 UTC Dan suggested adjusting TMS alignment. This brought the X arm green power over 1. Guardian moved on. 07:44 UTC Reloaded TJ's script on video5 per his earlier request. DRMI alignment looks bad, misaligned SRM to lock on PRMI, did not help 07:50 UTC Started initial alignment per Dan's suggestion 08:35 UTC Darkhan left. Kiwamu and Dan still here. 08:38 UTC Got to and stopped at DC_READOUT_TRANSITION. Dan modifying guardian to run measurement on OMC. 08:48 UTC Kiwamu left. Just Dan and I here. 08:57 UTC Checked that the PSL cameras are not frozen. Lights are off in the PSL enclosure. Checked mid and end station cameras. All dark, but end X does not move. mid Y still has flickering green lines. Lights are on in the LVEA. 09:03 UTC Dan starting measurement. 09:58 UTC Dan stopping measurement. Investigating possible issues with calibration left over from measurement. 10:52 UTC Observing mode. More ETMY saturations.
When we got back to low noise at 0958 UTC, we noticed the DARM gain was too low by about 30%. This was probably because we performed the gaurdian steps out of sequence: we increased power on RF DARM to allow for OMC modescans, with the DARM boost on, and then handed of to DC readout. Performing the RF-->DC handoff with the DARM boost enabled can spoil the coherence of the gain-matching calculation and lead to a value for the OMC-READOUT_ERR_GAIN that is off by tens of percent. Really we should be doing this calculation with a driven excitation, rather than relying on unsuppressed length fluctuations to provide coherence between AS45_Q and DCPD_SUM. But we haven't taken the time to code up a tdssine measurement (or tdsresp? something in cdsutils?) in the OMC guardian.
Anyways after some head-scratching we adjusted OMC-READOUT_ERR_GAIN so the height of the 331.9Hz calibration line was the same as it was twelve hours ago.