Yesterday I checked the POP sensing for MICH, PRCL and SRCL in full lock. I rephased POP9 and POP45 for a 92.6 Hz injection on PRM (because I found some already existing notches in the loops around this frequency). FTR, it's better to phase POP45I for PRCL, the dominant term, such that Q is free for MICH and then tune the PRCL subtraction in SRCL sensing. See plot attached of before (refs) and after phasing and retuning.

The POP9 phase change from -26 to -16.25 degrees and the POP45 phase changed from 6.1 to 12.0 degrees. The SRCL 9I element changed from 0.04 to 0.024. Changes have been absorbed in sdfs and guardian.

I then swept the loops to see the UGFS:
MICH - 8Hz
PRCL - 36 Hz
SRCL - 13.5 Hz

I saved the measurement templates in /opt/rtcds/userapps/release/lsc/h1/templates/ , names beginning with 190317*.xml

This should help with PRCL coupling into DARM, but we should recheck the SRCLFF performance.