SudarshanK, GregM, RickS

The SenseMon range shows an increase in range from about 63 Mpc to about 75 Mpc from the previous to the current lock stretch.  JeffK suspected this is the result of a change in the sensing function.

GregM used the SLM too to generate 60-sec FFTs of the calibration lines and we calculated the time varying parameters (see T1500377) using these data to assess changes in the sensing function.

The resulting kappa_C, the sensing function variation, as well as f_c, the coupled cavity pole frequency, are shown in the first plot attached below.  The second plot shows the SenseMon range over the past 12 hours with the step in the IR between the current lock and the previous lock.

It seems that the change in sensitivity is indeed the result of variatioins in the sensing function which are tracked by kappa_C.

Note that we are not currently compensating for changes in the sensing function, but we plan to be soon, when the GDS calibration is up and running (and compensating for kappa_C).