Dan, Corey

Tonight we followed up the measurement of ITMX's bounce mode Q with a measurement of the roll mode.  Same procedure: flipped the sign on the damping gain, excited the mode, zeroed the damping gain, allowed the mode to decay.

This time we lost lock after two hours, but this was enough for a clean measurement.  Also, as mentioned in a comment to the bounce mode entry, I did a better job of anti-aliasing before decimating the data for demodulation, and the fit to the RMS channel and the fit to the demodulated data are in good agreement.

RMS channel: 456,700

Demodulated DARM_ERR: 458,000

The mode frequency is 13.978Hz, plots attached.  Btw, I chose ITMX for these measurements because it receives the least amount of actuation -- ETMY gets DARM_CTRL, both ETMs are controlled by DHARD and CHARD, and ITMY is used for the SRCL FF.  We feed DSOFT and CSOFT back to the ITMs, and they both have oplev damping in pitch, but these loops should have very little gain at the bounce/roll frequencies.  (Also there are bounce/roll bandstops in the L2 and OL filter banks.)  So, there's not much chance that the ITMX modes are being damped/excited by control loops.