J. Kissel,

With only one more week to go on O1 "proper," (see JRPC Wiki), I think we've made the right gamble on not flipping the bias sign (as decided in the last two weeks, see LHO aLOG 24241, and 24383) -- the acceleration of the H1 SUS ETMY ESD's relative actuation strength accumulation in longitudinal is sufficiently negative that we will stay under the desired 10% systematic error in the calibration for at least another week or two (without correcting for the change, which we will do in the future). As usual, H1 SUS ETMX, (though inconsequential) shows a completely tolerable level of charge, and hasn't really moved since we've begun turning OFF the EX ESD Bias Voltage when its not needed. See attached trend plots. 

The new question is now "when and in what order do we make changes to the DARM loop?" We know we want to do the following (see G1501372):
    - Clean up the QUAD's longitudinal hierarchical control filters -- converting them all the distributed, and then chosing a better frequency distribution such that we don't need nearly as many violin mode notches, and which ever we do need don't impact the shpae of the over-all super actuator. 
    - Jack up the boost on the DARM filter to get more low frequency suppression.
    - Reduce the EY Bias Voltage by 2 to reduce the rate of charge accumulation.
    - Flip the EY Bias to reduce whatever chare has accumulated over the course of the run, such that we hit zero at the start of O2 and stay there.
    - (maybe move to a true DARM drive?)
Each of these tasks, once complete, will require a re-assessment of how close we are to saturations at each isolation stage. Further we should be sure to perform these changes slowly and methodically such that we understand the impact at every step and ensure that we retain IFO robustness (and *maybe* try to keep the DARM loop model and calibration up to date, if it's not too arduous). Part of slow and methodical is asking in what order we perform the above steps, and how much time should we use to reassess robustness in betweeen each step. Given that O2 prep is slated to begin mid-July (see G1501561), I think we can do these 4 (or 5) tasks over the course of a month and still have plenty of time to assess robustness. Further, since 
    - it's unclear how much up-time we'll have during the commissioning period to measure the longitudinal strength change via PCAL, 
    - there are also plans to make changes to the tracking of longitudinal actuation strength (see, e.g., Integration Issues 1138, 1170, and 1155)
    - making changes to the DARM loop as described above will mean that we'll need to get a new DARM model up and running before valid kappa's can be produced
I suggest we continue to make these charge measurements once a week throughout the commissioning period. Though we've (sadly) shown that the optica lever charge assessments are not exactly proportional to the longitudinal assessments from PCAL, the assessment is still close enough that it'll do.