Ground-based adaptive optics coronagraphic performance under closed-loop predictive control

TL;DR

This paper presents a semi-analytic framework to evaluate and improve ground-based adaptive optics coronagraphic performance using predictive control, significantly enhancing contrast and reducing observation times for exoplanet imaging.

Contribution

It introduces a semi-analytic model incorporating predictive control in AO systems, demonstrating potential contrast gains of over 1400 times at certain angular separations.

Findings

Predictive control can improve raw PSF contrast by over 1400 times at 1 λ/D.

Contrast gains of more than 30 times for stars similar to Proxima.

Enhanced contrast reduces required integration times, aiding exoplanet characterization.

Abstract

The discovery of the exoplanet Proxima b highlights the potential for the coming generation of giant segmented mirror telescopes (GSMTs) to characterize terrestrial --- potentially habitable --- planets orbiting nearby stars with direct imaging. This will require continued development and implementation of optimized adaptive optics systems feeding coronagraphs on the GSMTs. Such development should proceed with an understanding of the fundamental limits imposed by atmospheric turbulence. Here we seek to address this question with a semi-analytic framework for calculating the post-coronagraph contrast in a closed-loop AO system. We do this starting with the temporal power spectra of the Fourier basis calculated assuming frozen flow turbulence, and then apply closed-loop transfer functions. We include the benefits of a simple predictive controller, which we show could provide over a factor of 1400 gain in raw PSF contrast at 1 $\lambda/D$ on bright stars, and more than a factor of 30 gain on an I = 7.5 mag star such as Proxima. More sophisticated predictive control can be expected to improve this even further. Assuming a photon noise limited observing technique such as High Dispersion Coronagraphy, these gains in raw contrast will decrease integration times by the same large factors. Predictive control of atmospheric turbulence should therefore be seen as one of the key technologies which will enable ground-based telescopes to characterize terrrestrial planets.