Overcoming the effect of pupil distortion in multiconjugate adaptive optics

TL;DR

This paper introduces PropAO, a Python-based simulation tool that models pupil distortion effects in multiconjugate adaptive optics, specifically aiding solar astronomy by improving wavefront correction strategies.

Contribution

The paper presents PropAO, the first simulation tool to model pupil distortion effects in MCAO systems, enabling testing of advanced reconstruction strategies for solar telescopes.

Findings

PropAO accurately reproduces pupil distortion effects.

It facilitates testing of non-linear wavefront reconstruction methods.

Useful for optimizing European Solar Telescope's adaptive optics.

Abstract

Multiconjugate adaptive optics (MCAO) systems have the potential to deliver diffraction-limited images over much larger fields of view than traditional single conjugate adaptive optics systems. In MCAO, the high altitude deformable mirrors (DMs) cause a distortion of the pupil plane and lead to a dynamic misregistration between the DM actuators and the wavefront sensors (WFSs). The problem is much more acute for solar astronomy than for night-time observations due to the higher spatial sampling of the WFSs and DMs, and the fact that the science observations are often made through stronger turbulence and at lower elevations. The dynamic misregistration limits the quality of the correction provided by solar MCAO systems. In this paper, we present PropAO, the first AO simulation tool (to our knowledge) to model the effect of pupil distortion. It takes advantage of the Python implementation of the optical propagation library PROPER. PropAO uses Fresnel propagation to propagate the amplitude and phase of an incoming wave through the atmosphere and the MCAO system. The resulting wavefront is analyzed by the WFSs and also used to evaluate the corrected image quality. We are able to reproduce the problem of pupil distortion and test novel non-linear reconstruction strategies that take the distortion into account. PropAO is shown to be an essential tool to study the behavior of the wavefront reconstruction and control for the European Solar Telescope.