A BruCo scan for the "improved spectrum" mentioned in 47011 is available at the link below:
https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_lho_1234697418b/
I didn't use exactly the same time as in the posted spectrum, but instead used a quiet period with good range.
Some highlights:
- Coherence with SRCL at low frequency (<13 Hz) and around 25-30 Hz (fig 1)
- Angular noise as witnessed by ITMX_L2 below 40 Hz (fig 2)
- High coherence with OMC_A_PIT_OUT below 20 Hz and around the big lines (fig 3) Not sure how to interpreter this
- At high frequency, there's coherence with ISS signals (fig 4)
- Also, there's coherence with PEM-CS_ADC_5_20_2K_OUT_DQ and PEM-CS_ADC_5_21_2K_OUT_DQ. What are those? (fig 5)
The effect of a linear noise subtraction of ASC and LSC control signals is shown below. This subtraction uses the parametric technique described in T1800552.
The coherence with ASC-OMC_RIN_OUT_DQ and similar signals is due to the fact that at low frequency the DARM noise is large enough to dominate over those signal sensing noise. This has been confirmed by taking the transfer function ASc-OMC_RIN / DARM_IN1 during a DARM injection and using it to project ASC-OMC_RIN_OUT_DQ into DARM.