Not sure if anyone has already caught this. Switching the ETMX blend to Quiet_90 on Dec 14th caused glitches to appear around 20Hz region (Fig 1 - starting at 20:00:00 UTC.) while switching both ETMX and ETMY to Quiet_90 everywhere caused gliches to appear around 10 Hz and 30 Hz region (Fig 2 - starting at 9:00:00 UTC). Wind speed has been low (<5mph) and the useism (0.03-0.1Hz) has been around 0.4 um/s. BNS range has been glitchy since the blend was switched but the lock has been relatively more stable. The question is, do we want clean data but constantly risk losing lock when the tidal rings up, or slightly glitchy data but relatively more stable interferometer?
Tried switching ETMX X to 45 mHz again. Looking good so far.
After talking to Mike on the phone we decided to try switching both ETMs back to 45mHz blend. I'm doing this slowly. One dof at a time. Things got better momentary when I switched ETMX X to 45 mHz blend but soon tidal and CSOFT started running away. I had to leave ETMX X at 90 mHz. Out of Observing from 11:58:07 - 12:11:02 UTC.
And the tidal is back... I switched ETMX X to 90mHz. 45 mHz is used everywhere else.
Switching to the 90 mHz blends resulted in the DARM residual becoming dominated by the microseism. The attachment shows the residual before and after the blend switch on the 14th; the rms increases from 5×10−14 m to 8×10−14 m.
As a first test in eliminating this nonstationarity, we should try engaging a boost to reduce the microseism contribution to DARM.
The other length loops (PRCL, MICH, SRCL) are not microseism dominated.
Similar to DARM, the dHard residuals are microseism-dominated and could also stand to be boosted, although this would require some care to make sure that the loops remain stable.
[Also, the whitening filter for the calibrated DARM residual is misnamed; the actual filter is two zeros at 0.1 Hz and two poles at 100 Hz, but the filter name said 1^2:100^2. I've changed the foton file to fix this, so it should be reloaded on next lock loss.]
