Just got locked again after Niko had several hours of rough weather. Wind is only somewhat less bad than before. The only thing I changed to successfully get locked was turn on the arm cps differential controls (I took SEI_DIFF to FULL_DIFF_CPS). Microseism is high, so scatter is bad, and our range is taking a beating, which is not unexpected, but the ADS lines are not swamped, we seem to be stable.

First attached plot is the state numbers for the ISC LOCK and SEI DIFF. The dip in the blue line is where I switched SEI_DIFF to FULL_DIFF_CPS at about 4000 seconds in, you can see after that after that I was able to get to NLN, and we've been in OBSERVE since.

Second attached plot shows 2.5 hours of winds at the ends and corner for the same time as the first plot. The blue corner station wind is consistently higher, maybe because that sensor is more affected by the flow accelerating over the building? Or Maybe the fences are doing there jobs? The low frequency blrms on the wall seem to show less separation between the CS vertical eq band blrms and the end horizontal blrms than we used to see. Worth a different study. But, you can also see that CS winds actually increased while we were locking after the SEI_DIFF switch at 4000 seconds. The ends rolled off a bit for a while, but seem to be back up again, now.

The third plot are some channels from the endstation BRS, being the best direct ground tilt sensors we have. The top plot is the .03-.1hz blrms from each brs, you can see that EY is consistently higher, and it kind of rolled off around the time I switched SEI_DIFF, but it comes back higher at the end of this window.

These BRS blrms channels (just like we have for the ground STS) seem like they could be really useful for environmental studies, but I don't think they've gotten a lot of attention. For, instance, I would guess that without FULL_DIFF_CPS 5 nrad/s in the .03-.1hz blrms is a useful threshold, we couldn't seem to lock when BRSY was hitting this level, but when we had the arm cps diff on we got up to 7 nrad/s and it was okay. Worth looking at more.

Bottom subplot for the third plot is the velocity readout from each brs, it's a bit contaminated by the brs resonance, not sure what else this shows other than it didn't get quieter.

The takeaway, I think, is the even if the microseism is high, if the wind is bad and preventing locking, it maybe worth it to go to the FULL_DIFF_CPS. This is something we will have to think about