This afternoon we were preparing to increase the CO2_X power; we wanted to measure intensity noise but found the ISS second loop slow offset servo was saturated. It looks like in this lock, when we DC-coupled the second loop the output to the slow servo just ran away (see first attachment, top right is the slow servo output). Perhaps when we held the output of the AC coupling servo it was too far away from the mean (top left trace)? Sheila looked back in time several months and a saturation of this scale has not occurred before. She slowly ramped the gain to zero, which caused the diffracted power to increase from 2.5% to 3.2%.

We have left this servo off for now, and accepted a few PSL-ISS related SDF differences.

To clarify: for the duration of this lock the ISS second loop slow feedback has not been nominal, from ~1241739043 to ~1241809666 the digital servo was saturating, and after this time it was turned off. This has not affected the lock.