I retuned the ITMY A2L gains today to reduce CHARD coupling to DARM. I followed the same process Gabriele and I followed when we did this at 76W, alog 69082.
- I turned on all ASC 8.125 Hz notches
- I turned on the ADS lines (out of an abundance of caution, I probably didn't need to do this)
- I injected an 8.125 Hz line into CHARD P SM EXC using awggui
- I adjusted the ITMY P2L gain to reduce the height of that peak in DARM
- I turned off this excitation and then repeated the process with CHARD Y and the Y2L gain
- I turned off the notches and took us back to camera servos when finished
New gains:
P2L: 0.1
Y2L: -0.2
Old gains:
P2L: -0.05
Y2L: -1.7
I was able to reduce the CHARD P line height in DARM by about a factor of 4, and the CHARD Y line height in DARM by about a factor of 10. These are similar to the values that Gabriele achieved at 76W. See attached plot, OMC DCPD SUM reference was the starting point, live trace was the end point with new A2Ls.
I updated the guardian to use these new A2L gains. These gains will be engaged in the move spots state when we adjust all the other A2Ls (as usual). I loaded the guardian after the change. I did not see any SDF diffs related to this change in observe, so I guess these channels are not monitored? There is no need to SDF in safe as these are guardian controlled.
I gave the A2L gains another look, still injecting a CHARD line at 8 Hz. I made some improvement to both pitch and yaw with P2L = -0.1, and Y2L = -0.15. I think we see a small reduction in noise below 10 Hz from this change. The CHARD P coherence is also slightly reduced as a result. The new gains are in the guardian. I gave these another look because we have evidence of an alignment change from the new OM2 TSAMS setting, and we did see the ASC coherence change with the OM2 setting.