Rick S, Sudarshan K, Travis S, Jeff K, Darkhan T,

We uploaded the updated force coefficients (N/V) into the PcalY filter file. This has effect on following calibrated outputs:

H1:CAL-PCALY_TX_PD_OUT*
H1:CAL-PCALY_RX_PD_OUT*

Calculation of the factors is described in T1600520-v1. Relevant sources (other T documents containing WS, GS and end-station calibrations) were referenced in that document. The Matlab script that produced the factors is attached to the document above and also can be found in CalSVN (or a newer version of the script in the same directory):

https://svn.ligo.caltech.edu/svn/aligocalibration/trunk/Projects/PhotonCalibrator/scripts/pcalEndstation/pcalForcecoefficient.m

The old and new values are listed below:

• TxPD: old value 1.515^-9 N/V, new value 1.516^-9 N/V, changed by 0.07%.
• RxPD: old value 1.049^-9 N/V, new value 1.0475^-9 N/V, changed by 0.14%.

One can notice that these values are nearly identical, which is a mere coincidence. We consider PCALY is now in a new epoch w.r.t. O1 time because we adjusted beam positions on the ETM (also addressed clipping at RxPD integrating sphere) and we adjusted the angle of the transmitter module beamsplitter which adjusts the power balance between the two beams (see LHO alog 30877).