15:55 David N. through gate Had trouble locking on DRMI. Tried locking on just PRMI. Had a few locks on PRMI, but would not stay. Eventually gave up and started an initial alignment at 17:47 UTC. Finished initial alignment with help from Sheila at 18:55 UTC. Had trouble with ALS during initial alignment. Sheila and Jenne now suspect we may be losing lock engaging the gain for the DSOFT loop. They are starting a test now.
[Sheila, Patrick, Jenne]
We discovered that the problem was we had some medium-large offsets on the input of the SOFT yaw loops, and when the gain was being increased in ENGAGE_ASC_PART3, the loops started to run away.
For this lock, we hand-ran the "main" part of ENGAGE_ASC_PART3, which turns the loops on with low gain. Once the loops had converged (~ 10 minutes for all of them to finish!), we let guardian run the full ENGAGE_ASC_PART3 state, and continue on. We have just arrived at NOMINAL_LOW_NOISE, and we don't have any SDF diffs, so there is no net change in the configuration of the IFO.
We would like to think about putting a "convergence checker" in this guardian state, so that it waits until the loops are happy before continuing. Sheila has implemented this with great success several weeks ago in the DRMI ASC parts of the guardian code, so it should be relatively simple to do the same thing for the arm loops.