It looks like usually the PSL PMC + FSS can stay locked for long periods of time, for example >1 month over the emergency vent in August. See the attached trends of the # of locked days and hours in the last few months (ndscope saved as /ligo/home/victoriaa.xu/ndscope/PSL/pmc_fss_can_stay_locked_over_emergency_o4b_vent.yaml).
The last time the PMC was locked for almost a month ended on Sept 23, 2024. Since then the PSL PMC has not stayed locked for over 5 days, but this is most likely due to commissioning tests and debugging which started around then.
Some trends showing several PSL signals over O4b, and the end of O4a.
Key points- PMC + FSS stayed locked continuously during both the O4a/b break (Feb 2024), and the emergency vent (Aug 2024), with minimal glitching in PMC TRANS and Ref Cav Trans PD (FSS-TPD).
Trying to compare PSL-related spectra between the original O4 NPRO and the current NPRO using DTT is kinda confusing.
Comparing times with before O4 NPRO from 21 Oct 2024 04:55 UTC (blue, 169 Mpc), and now with O3 NPRO at 16 Nov 2024 08:20 UTC (red, 169.9 Mpc).
For the fast mon spectra in the top left plot, FSS FAST MON OUT looks 2-5x noisier now than before. H1:PSL-FSS_FAST_MON_OUT_DQ calibrated into Hz/rtHz using zpk = ([], [10], [1.3e6]) (see 81251, this makes H1 and L1 spectra into comparable Hz/rtHz units 81210).
But for FSS-TPD (ref cav trans), it looks like there's some extra 1-10Hz noise, but otherwise the trans spectra might be quieter? Similarly confusing, the ISS AOM control signal looks quieter. Not a clear takeaway from just these spectra on how to compare O3/O4 NPROs.
