I ran a BruCo scan of last night's lock (GPS 1160787977 + 600s). The full report is available here. As pointed out by Sheila et al, the low frequency region (below 100 Hz) doesn't show much coherence with anything (low coherence with MICH/SRCL, fig 1 and 2, a bit with angular controls, fig 3 and 4, but lower than usual.)
In the jitter region, there are the usual coherences with IMC WFS and signals. However, I found interesting coherences with a few more channels in this region
- coherence is quite high on the peaks with PSL-ISS_PDB_REL_OUT (fig 5), while there is a kind of broadband lower floor of coherence with PSL-ISS_PDA (fig 6)
- coherence similar to PDB is present with PSL-ISS_AOM_DRIVER_MON_OUT (fig 7)
- high coherence also with LSC-REFL_SERVO_CTRL_OUT (fig 8) and related error signals (LSC-REFL_A_I/Q_ERR, not that there is coherence with both I and Q, although lower in Q, figs 9 and 10)
- also there is coherence, at similar levels, with the PMC control: PSL-PMC_HV_MON_OUT (fig 11)
I'm not sure what to make of all those coherences, since coupling through intensity or frequency noises were almost ruled out...
Finally, the DBB channels are not available in the science frames that are read by BruCo, so I separately computed the coherence with the DBB QPDs. Figure 12 shows the usual coherence with the DBB_QPD_1QY signal.
