I have measured transfer functions and spectra for the PR mirror.

- Figure 1: TF when injecting noise in YAW

- Figure 2: TF when injecting noise in PITCH

- Figure 3: spectrum YAW (comparison open and closed loop)

- Figure 4: spectrum PITCH (comparison open and closed loop)

NB. It seems that there is some acoustic noise: I did the measurement with the light switched off but the chamber was open and I didn't put any boxex around the laser and the PSD

While looking at the error signals in the past days I have noticed that often some strong oscillations at 1 Hz and 3 Hz were present (see figure 5). We observed it also in the past and we were suspecting the stack vibratiion introduced by the steering mirrors used for the optical lever ( see entry 276:  the attached spectra taken last july are very similar to those of fig 5)

Since this oscillation is not present when the intermadiate mass is well centered on the magnet older plate (as it was just after the mirror installation or today after that I performed the check on the yaw motion) and it appeared after we tried to move as much as possible the yaw picomotor yesterday, I think it is caused by the intermediate mass touching the magnet holder plate.