Open-loop wavefront sensing in the presence of speckle and weak scintillation

In this paper, we show that speckle averaging helps to reduce the measurement error associated with a Shack–Hartmann wavefront sensor (SHWFS); however, this reduction is rendered ineffective with increasing beacon anisoplanatism. We do so operating in a weak-scintillation regime, where the SHWFS offers robust performance, and using in-plane translation of the illuminated rough surface to accomplish frame-to-frame speckle diversity. Understanding these trade-space limitations is critical when performing wavefront sensing with noncooperative, extended-source beacons. • We derive analytic estimates for RMS wavefront error/aberration in vacuum/turbulence. • We present a new modeling framework to simulate partially correlated speckle frames. • We report simulation results in wavefront error/aberration and irradiance skewness. • We demonstrate the benefits of speckle averaging under isoplanatic conditions. • We identify potential drawbacks of speckle averaging in anisoplanatic conditions.