Sheila, Sundae

During the maintenance, we did a measurement on coupling between the L2 Length (L2) to test mass pitch (P3) and yaw (Y3) between 2 Hz and 10 Hz. We excited the length at L2 and measured the L3 pitch and yaw change with swept sine response. 

The plot shows the measurement data compared with the model. The coupling from L2 to P3 agrees with the model as expected between 2 Hz and 4 Hz. Above 5 Hz, the coherence dropped below 0.1 indicates that we did not have enough driving on L2 to see the coupling. We did not have a good model for L2 to Y3 coupling yet, so we did not expected a good agreement for the L2 to Y3 coupling. Measurement with more points need to make in the future with higher driving above 5 Hz.