As promised, this morning I took a new measurement of the JAC reflected beam on wavefront sensors A and B. This time, we unlocked the JAC, which provided a cleaner beam for centering in both pitch and yaw. The results were much better, with the relative differences between segments reduced to below about 10%.

As a sanity check, we compared the measured and calculated G1/G4 ratios for WFS A and WFS B, as shown in the attached table. For WFS A, the discrepancy is about 10%, while for WFS B, it is only about 2%. We think the remaining error may come from beam clipping when we attempted to recenter the beam between the two halves, the approximately 1 mm gap between the quadrants, or pitch-yaw cross-coupling.

Overall, this measurement gives us an estimate of the uncertainty associated with this technique for measuring the relative segment gains.