J. Kissel

Summary
We're adding three new calibration lines around 30 Hz on the ETMY actuation stages in order to narrow down the uncertainty in actuation strength independently for each stage. Depending on the success of their analysis, and interference with IFO operations, we'll decide whether to leave them on for ER9. We may also push further forward with cancelling these lines with the Y-end PCAL, but for now, I turn them on without cancelling for the week prior to ER9. We may also push further forward an cancel these lines with the Y-end PCAL, but for now, I turn them on without cancelling for ER9.

Motivation
Recall that during O1, H1 had a static, ~2% systematic error in the collective actuation strength ("kappa PU"), narrowed down using cumulative integration time allowed for by the overall DARM loop line coupled with the ESD-only line (see e.g. LHO aLOG 24569 or LHO aLOG 25031). We intend to differentiate between the strength of the upper stages for the future, using their constant presence to bring the uncertainty in relative actuation strength to be essentially zero. Once we cancel these lines with PCAL, that'll bring the absolute calibration uncertainty to essentially zero.

Line Details
For now, without the man-power for further study of their "optimal" location, I've just stolen L1's ~30 Hz calibration line frequencies from O1 (see original source T1500377), given that they'll not be involved in ER9. The details of the new lines are:
Isolation Stage        Frequency        Amplitude     Oscillator Channel
TST / L3                 35.3              0.11       H1:SUS-ETMY_L1_CAL_LINE
PUM / L2                 34.7              1.1        H1:SUS-ETMY_L2_CAL_LINE
UIM / L1                 33.7              11.0       H1:SUS-ETMY_LKIN_P_OSC

These new values have been accepted into the DOWN and SAFE SDF files.
This is in addition to the "normal" calibration lines from O1 that will still be on such that we can replicate the O1 calculation without extra effort.

On the TST / L3 stage, we now have *two* calibration lines, and this is such that we can still reproduce the O1 calibration line, time-dependent parameter tracking without changing anything. However, because we're not yet confident enough in the PCAL cancelling scheme for it to completely replace the O1 method, and we haven't installed / replaced any infrastructure. Thus, for now, I've stolen one of the Optical Lever Lock-in Oscillator and piped it out to the DAC output as a longitudinal drive using the LKIN2ESD matrix.