Kiwamu, Jamie, Lisa
Today we had the illusion that we could start locking before dinner time, but that didn't happen.
While both the X and Y arms were locked on green, something happened in the corner station (visible in the PEM CS SEIS 30-100 mHz channels, especially Z) which affected only the Y arm, while the X arm remained happily locked.
I added a very-low-frequency-boost in the BS oplev damping loop which reduces the motion between 10 mHz to 100 mHz.
When seismic was high as Lisa reported, BS also moved a lot in yaw by 1.5 urad in pk-pk. This was causing a power modulation in the ALS diff beatnote. So I added this filter to reduce the motion at very low frequencies. Also, I increased the gain for this loop from -0.03 to -0.05 as there was a servo instability at 1-ish Hz with the VLF boost engaged. When seismic is at the normal level, do not forget to disengage this VLF boost.