Extracting the scalloping error from closed loop AO data

In this paper, we present an algorithm and supporting simulations results showing how a single conjugated AO system can be used to detect a scalloping error occurring in the telescope. We show that when the scalloping error modes are entered in the reconstruction modal basis, the Deformable Mirror shape can be used to estimate the scalloping error through a simple matrix vector multiply. Temporal averaging allows to get rid of the atmospheric noise on the scalloping measurement assuming a perfect “scalloping actuator” and to get a measurement accuracy of about 20nm rms.