Optical design trade-off study for the AO module of MAVIS

TL;DR

This paper presents a comprehensive optical design trade-off analysis for MAVIS, a new adaptive optics instrument for the VLT, focusing on optimizing system performance, compactness, and ease of alignment.

Contribution

It introduces multiple optical design solutions for MAVIS's AO module, evaluating their performance and practicality to guide implementation.

Findings

Identified optimal optical configurations balancing quality and compactness.

Compared solutions based on throughput, alignment, and distortion.

Provided recommendations for the system's optical design choices.

Abstract

MAVIS (MCAO-Assisted Visible Imager and Spectrograph) is an instrument proposed for the VLT Adaptive Optics Facility (AOF), which is currently in the phase-A conceptual design study. It will be the first instrument performing Multi-conjugate adaptive optics at visible wavelengths, enabling a new set of science observations. MAVIS will be installed at the Nasmyth platform of VLT UT-4 taking advantage of the already operational Adaptive Optics Facility that consists of 4 LGS and an adaptive secondary mirror with 1170 actuators. In addition, two post-focal deformable mirrors and 3 Natural Guide Stars (NGS) are foreseen for the tomographic reconstruction and correction of atmospheric turbulence. The MAVIS AO module is intended to feed both an imager and a spectrograph that will take advantage of the increased resolution and depth with respect to current instrumentation. In this paper we present the trade-off study for the optical design of the MAVIS AO module, highlighting the peculiarities of the system and the requirements imposed by AO. We propose a set of possible optical solutions able to provide a compact and efficient implementation of the different subsystems and we compare them in terms of delivered optical quality, overall throughput, encumbrance, ease of alignment and residual distortion.