MAVIS Adaptive Optics Module: optical configuration and expected performance

Abstract

The MCAO Assisted Visible Imager and Spectrograph (MAVIS) is currently in preliminary design for the ESO VLT. The instrument will provide multi-conjugate adaptive optics correction over a wide field of 30”x30”, feeding the visible part of the spectrum (from 370 to 1000nm) to an imager and a spectrograph. The Adaptive Optics Module (AOM) of MAVIS implements two deformable mirrors, composed by more than 2000 actuators each, and includes a Laser Guide Star (LGS) and a Natural Guide Star (NGS) wavefront sensor for the tomographic reconstruction and correction of the atmospheric turbulence. Moreover, it provides other key functionalities like atmospheric dispersion compensation and field de-rotation, delivering a corrected diffraction-limited 30”x30” focal plane to three output ports: one for the imager, one for the spectrograph and one for visiting instruments. In this paper we describe the current optical configuration of the AOM, and we report the results of the analyses conducted to evaluate the expected optical performance of the system. The analyses include simulations for the manufacturing and alignment tolerances, sensitivity to mid-spatial frequency figure errors and their impact to astrometry.