Summary:

Now the ISS second loop  RPN signals  ( H1:PSL-ISS_SECONDLOOP_SUM14_REL_OUT_DQ and   H1:PSL-ISS_SECONDLOOP_SUM58_REL_OUT_DQ) are normalized using the DC signals from the photodiodes.

Before:

The original electronics on the photodiode readout for ISS second loop had a whitening so we were not able to get the DC signals.    Temporary arrangments were made to monitor these DC signals by using testpoints but they were not included in the front end model.  To calibrate the output signals we were using  a  constant number (12 V in our case) which was obtained by taking the DC signals from the test point when the ISS was operating at its nominal configuration at about 2.8 W.  However, this calibration factor changes with the change in laser power.

After:

On our last  ISS second loop model update (see alog18381)  we included these DC channels into the front end model so we can acquire the DC signals from the photodiodes.  Now the ISS output signals are calibrated (normalized) using these newly acquired DC signals.  See attached filter module to see the changes that have been implemented.