Incorporating adaptive optics controls history in post-processing of ground-based coronagraph models

Abstract

© 2020 SPIE. The planet detection thresholds of space-based coronagraphs are predicted to lie within an order of magnitude from their theoretical (shot-noise) limits. Ground-based telescopes, on the other hand, are limited by larger systematic uncertainties in the point spread function (PSF) of the residual light which rapidly fluctuates due to atmospheric turbulence. The PSF is affected by Adaptive Optics (AO) which reduce the intensity of the speckles but also make them less predictable. Although not a common practice, it is possible to take millisecond exposures of the so-called "frozen"speckles and record the history of AO controls, in which case the collected data resembles that of simulated space coronagraphs. In this work we use the HEEPS simulation of the EELT/METIS to assess the applicability of this newly-developed space-oriented approach to ground-based postprocessing. Unlike intensity-based algorithms, this method formulates the estimation problem in terms of the electric field of the speckles and therefore can incorporate controls history and various temporal models of the electric field variations. In our simulations, we artificially introduced small deformable mirror (DM) probes on top of AO controls, and achieved a post-processing error lower by a factor of 2 than that of Angular Differential Imaging (ADI). However, our attempt at incorporating the AO history without DM probes, has so far resulted in higher errors than ADI.