Another go at the noise projection from MC1-3 pit/yaw to MC length. This time injecting into the MC autoalignment FB (e.g. C1:IOO-WFS1_PIT_EXC ).
LTPDA is working now, but still the NDS server is not so cooperative.
Summary: Alignment fluctuations of the MC mirrors don't significantly contribute to MC length changes up to at least 3.5Hz. Especially they can't explain the lack of coherence between seismometers and MC length below 1Hz that we worry about for the OAF.
At high frequencies >= 10Hz you can see angle to length coupling as is evident in Sureshes spot position measurements.
Injection from 0.1-20Hz.Filtered by the servo filters and zp:, , Gain = 1 @ 2Hz
Look at the coherence plots for the quality of the measurement:
DOF Amplitude[counts] UTC Time (duration always 4mins)
WFS1p 70 22:28
WFS1y 55 22:03
WFS2p 70 22:13
WFS2y 70 22:18
None - 22:23
To get some better SNR at low frequencies I did a fixed sine noise injection at 0.3Hz. See attached files.
DOF Amplitude[counts] UTC Time (duration always 4mins) Lower limit of SNR MC length via mirror misalignment
WFS1p 4 00:05 29.3
WFS1y 4 00:14 22.0
WFS2p 4 00:19 18.5
WFS2y 4 00:25 18.0