By measuring the transfer function from PR/BS p/y motion to Input/End diagonalized signals, we could calibrate PR/BS p/y motion to Input/End diagonalized signals. As a result, we could know how much PR and BS angular motion are contributing to the diagonalized AA signals (Input/End diagonalized signals).

Some measurement situation: The transfer function measurement was done without excitation. PR/BS local control was closed. 

Reconstruction method: Let's take reconstruction of Input_p as an example. Input_p = PR_p*TF + PR_y*TF + BS_p*TF + BS_y*TF. This means that we sum PR/BS p/y motion's contribution to AA diagonalized signal. (Here PR_p/y and BS_p/y signal is directly the oplev signal without any modification. The Input_p signal is also directly from DGS system)

The results are shown in attached figures. We could see that AA diagonalized signals are almost totally limited by PR/BS angular motions.