Sheila, Alexa, Kiwamu,

We noticed that occasionally the IMC locking loop kicks the FSS into a situation where the FSS oscillates for unknown reason.

We did not check what frequency the oscillation was, but this was visible in the PZT monitor in the FSS screen. It kept oscillating even after the IMC feedback onto FSS was disabled. We figured out that decreasing the common gain somehow fixes the oscillation. Strangely,  once the oscillation was gone, we could set the common gain back to the nominal of 30 dB without the oscillation. We believe that this oscillation is a part of the reason why the IMC did not recover right away when it looses the lock.

For the commissioning tonight, we reduced the common gain to 18.8 dB.