Characterisation of a turbulent module for the MITHIC high-contrast imaging testbed

TL;DR

This paper describes the development and characterization of a turbulence simulation module for the MITHIC high-contrast imaging testbed, aimed at improving wavefront correction for segmented telescopes.

Contribution

It introduces a new turbulence module for the MITHIC testbed and provides its detailed characterization using various instruments and sensors.

Findings

Successful simulation of static and atmospheric turbulence patterns

First coronagraphic measurements demonstrating the module's effectiveness

Enhanced understanding of wavefront errors in high-contrast imaging

Abstract

Future high-contrast imagers on ground-based extremely large telescopes will have to deal with the segmentation of the primary mirrors. Residual phase errors coming from the phase steps at the edges of the segments will have to be minimized in order to reach the highest possible wavefront correction and thus the best contrast performance. To study these effects, we have developed the MITHIC high-contrast testbed, which is designed to test various strategies for wavefront sensing, including the Zernike sensor for Extremely accurate measurements of Low-level Differential Aberrations (ZELDA) and COronagraphic Focal-plane wave-Front Estimation for Exoplanet detection (COFFEE). We recently equipped the bench with a new atmospheric turbulence simulation module that offers both static phase patterns representing segmented primary mirrors and continuous phase strips representing atmospheric turbulence filtered by an AO or an XAO system. We present a characterisation of the module using different instruments and wavefront sensors, and the first coronagraphic measurements obtained on MITHIC.