Multiconjugate Adaptive Optics for Astronomy

TL;DR

Multiconjugate adaptive optics (MCAO) enhances astronomical imaging by correcting atmospheric turbulence over larger fields of view, enabling near-infrared diffraction-limited images with improved accuracy for current and future telescopes.

Contribution

This review introduces MCAO principles, discusses its technical challenges, and presents performance results from existing systems, highlighting advancements over classical AO.

Findings

MCAO achieves Strehl ratios up to 40% in H band.

Full width at half maximum can be reduced to 52 mas.

MCAO improves photometric and astrometric accuracy.

Abstract

Since the year 2000, adaptive optics (AO) has seen the emergence of a variety of new concepts addressing particular science needs; multiconjugate adaptive optics (MCAO) is one of them. By correcting the atmospheric turbulence in 3D using several wavefront sensors and a tomographic phase reconstruction approach, MCAO aims to provide uniform diffraction limited images in the near-infrared over fields of view larger than 1 arcmin square, i.e., 10 to 20 times larger in area than classical single conjugated AO. In this review, we give a brief reminder of the AO principles and limitations, and then focus on aspects particular to MCAO, such as tomography and specific MCAO error sources. We present examples and results from past or current systems: MAD (Multiconjugate Adaptive Optics Demonstrator) and GeMS (Gemini MCAO System) for nighttime astronomy and the AO system, at Big Bear for solar astronomy. We examine MCAO performance (Strehl ratio up to 40percent in H band and full width at half maximum down to 52 mas in the case of MCAO), with a particular focus on photometric and astrometric accuracy, and conclude with considerations on the future of MCAO in the Extremely Large Telescope and post-HST era.