A brute force coherence report can be found here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1123740797/

I’m using data from Evan’s elog 

It took some time to process this since first data was not available on ldas-pcdev1.ligo-wa.caltech.edu due to some maintenance, and then my home folder was not available on ldas-pcdev1.ligo.caltech.edu due to some other maintenance. However, all’s well that ends well

• Below about 15 Hz there is coherence with DCPD_NULL, and this coherence is quite large in the 2-7 Hz region. I don’t know how to interpreter this, but I’m sure I’ve never seen it before (figure 1)
• There’s a bit of coherence below about 14 Hz with ASC-SRC2_Y (figure 2)
• Coherence with SRCL is at about 20%, so not limiting right now (figure 3)
• Coherence with MICH is somewhat higher, but still not limiting (figure 4). We are very close in the 35-45 Hz region.
• Between 15 and 30-40 Hz there is very large coherence with DHARD PITCH: this is limiting the sensitivity between 15 and 25-30 Hz! (figure 5) The same coherence is visible with ITMX and ITMY L2 coil signals (figure 6)
• Two “lines” at 27.25 and 28.25 Hz shows high coherence with PRCL
• In the regions 50-60 Hz there is some (not very high) coherence with ASC-X_TR_B_YAW. Is this beam jitter? (figure 7). Instead, between 77 and 78.75 Hz there is large coherence with ASC-X_TR_B_YAW_OUT (figure 7)
• Figure 8 shows the coherence with OMC-LSC_DITHER: there are few lines here an there that are coherent, even at low frequency (the lowest one is 64 Hz). Is this some kind of non-linear up/down conversion from the main dither lines? 
• At 64, 128 Hz and 256 Hz there is coherence with OMC-LSC_DITHER again but also with PEM_EY_MAG_EBAY_SUSRACK_X/Y/Z. Having coherence at 64, 128, 256 Hz is very suspicious!
• At 64 Hz there is coherence with a microphone (PEM-EY_MIC_VEA_PLUSY) and a magnetometer (PEM-EY_MAG_EBAY_SEIRACK_Z) and the end Y station
• Coherence with AS_A/B/C_SUM is still present at high frequency. This is our 45 MHz amplitude noise (figure 10). The same level of coherence is visible with ASC-OMC_A/B/C_SUM (figure 11)
• Good news is that the coherence with the periscope accelerometer is low (figure 12), although I still can guess the shape of the two bumps in the sensitivity…