Marc, Michael, and Yuhang

When we want to lock filter cavity today, we found it was harder to lock even with filter cavity z correction loop on.

To understand why this happens, we took measurement of oplev signal and checked weather information.

1. Oplev signal. In the attached figure one, four suspended mirrors oplev spectrum is shown. We can see the mirco-seismic noise between 0.2 and 0.8Hz is increased by a factor of 5 for BS/Input/End.

2. Tide/seawave/wind information: We checked Yahoo tenki, as shown in the attached figure 2,3,4,5, the tide is small tide, the sea wave height is around 3m, the sea wind is around 12.5m/s, the ground wind is around 5m/s.