Post-processing to deduce the piston, tip, and tilt values on the different segments from the phases reconstructed by COFFEE. First, we subtract the reference phase (obtained with COFFEE when the Iris-AO is at its best flat) to obtain the residual piston/tip/tilt to be corrected. The residual phase is multiplied with a hexagonal mask to isolate the segment of interest. We apply a dot product to this segment phase with a hexagonal calibrated Zernike polynomial to compute the aberration amplitude, that can be compared to the command that has been sent to the Iris-AO. The output value, here −127.561 is in nanometers.