A while ago Robert helped me resurrect the T240 in the BRS enclosure at EY, which we want to see if we can use to get better subtraction from the BRS during windy times. Right now, it seems like the T240 sees more low frequency noise than the ground seismometer we currently have on the ground outside the BRS box, during both a quiet time last night and during 30mph winds on the 7th. First plot shows the asds during both times. Red, dark blue and bright green are during the windy time, dark green, pink and light blue are during the quiet time. For both times, the T240 in the enclosure shows more noise noise below .1 hz than the ground STS. It could be that there is more temperature variation for that seismometer or it's platform. During the quiet time, this extra noise probably wouldn't be a performance issue, if we used this sensor for feedforward, but I haven't looked at the effect  on the isi controls during windy time

But the coherence with the BRS is slightly better, shown in the second image. The red line on the second plot is the coherence during the windy time between the BRS and the ground STS, the dark blue line is the coherence from the enclosure seismometer with the BRS, and most places the blue line is slightly higher than the red. It is also interesting to compare the bright green and light blue lines, which are the coherence between the two seismometers during the two different times. I'm a little surprised how much coherence there is between the seismometers during the windy time (bright green line), I kind of thought we "knew"  the coherence lengths for tilt were too short for that much coherence. This seems to be true for the light blue line, which is the coherence between the seismometers during the quiet time.