With the offset on the AS_A WFS centering, that should lower DHARD_Y coupling to DARM:
https://ldas-jobs.ligo-wa.caltech.edu/~gabriele.vajente/bruco_1394535464_DARM
Indeed, DHARD_Y coherence with DARM is much lower. Interestingly, now CHARD_Y coherence seems higher.
In other news, there is some coherence with MICH, but hopefully the retuned FF filter will help with that.
Coherence with input jitter witness is also large, see for example the PSL periscope
[Trent, Georgia]
We were curious if the coherence between DARM and the PSL periscope accelerometer was improved with Craig's Wednesday night input alignment. Though there wasn't much time without glitches or excitations during this lock, we got a 700 averages with 75% overlap bw 0.1Hz. In the attached plot, top is DARM ASD, bottom is coherence with the PSL periscope accelerometer (witness sensor for jitter), and right plot is zoomed in on some of the jitter peaks. It looks pretty convincing that for the resonances above 100Hz, the coherence was lower with the new input (and full IFO) alignment on Wendesday.
According to some of the sensors in HAM2 and HAM3, we might have walked the input pointing further in PIT than the O4A alignment, so maybe there is an IM1 and IM3 alignment somewhere in between the two times in the attached plot that has even lower input jitter coherence.
Attachment shows DARM × PSL acceleration coherence on 13 Dec (red), 11 Jan (turquoise), and 16 Mar (black). There is no significant difference between the latter two.
OM2 was hot on 13 Dec and cold on the latter two.
