In alog 48378, when comparing the broadband + sweeps measurements (CALCS) to pyDARM (GDS), an overall 40-microsecond delay is required to get make the two results consistent with each other, which is not understood.

After step-by-step investigation and fixing a few bugs in the following two scripts, the 40-microsecond delay mystery is solved. Now by applying the R_GDS/R_CALCS corrections, the blue dots are corrected to green dots (see attachments). Details are documented in T1900169

Broadband: /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Scripts/CALCS_FE/process_broadband_pcal_20190410.py
Sweep-sine: /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Scripts/FullIFOSensingTFs/process_sweep_pcal2darm_20190410.py

The steps are: (see details in the scripts)

1) The delta_C and delta_A are obtained by using the following variables:

delta_C = sensProd.calcsResid2gdsInvSensOut  
delta_A = actProd.calcs2gdsResidActFiltOut_NoDAQDownSample_removeCALCSdelay #The DAQ downsampling is not used in CALCS, so we do not include it

2) The delay between C and A in CALCS is not seen by GDS. So we need to correct it.

R_cor = (1/delta_C) * (1+C*A*D) / (1 + C*A*D / (delta_C * delta_A / delay_between_C_and_A))

When taking the 0410 measurements at LHO, a 7-cycle delay was installed. (not 9 cycles updated after processing the measurements).

Also we have fixed the script of computing relative delay between A and C (Scripts/CALCS_FE/compute_relativedelay_AvsC_20190404.py) Now the correct delay estimate for 0404 model is 7.7 cycles. (See attachment) We will install 8 cycles.

3) Apply dewhitening (from CS_DARM_DELTAL_EXTERNAL_WHITEN filter)

4) Apply the total PCAL correction sensProd.pcalCorrection

The comparison between the sweep-sine measurements and the uncertainty envelope is also updated (see attachment).