Optical Design for the Adaptive Secondary Setup and Instrument Stimulator (ASSIST)

摘要

A comprehensive suite of Adaptive Optics systems and AO-assisted instruments is currently under development for the VLT and will be built around a hyperbolic convex adaptive Deformable Secondary Mirror (DSM). In telescopes with such a secondary mirror, test and calibration of both the DSM and the science instruments using it are notoriously expensive and time-consuming. The Adaptive Secondary Setup and Instrument Stimulator (ASSIST) is being developed to allow test and integration of three key elements of the future VLT Adaptive Telescope Facility: the DSM and 2 instrument-specific adaptive optics systems (GALACSI for MUSE and GRAAL for HAWK-I). The core of ASSIST is a standalone interferometric test setup for the DSM allowing its test at its center of curvature (significantly reducing the size of the classical hyperbole focii test configuration). This setup is completed by a star simulator for both natural and laser guide stars, a turbulence generator (for realistic AO performance measurements), a corrector system generating a VLT-like exit pupil and a Nasmyth rotator simulator interfacing with the two AO systems. In this paper we present the optical architecture of ASSIST, detailing the current design of the different parts of the system, and discuss its projected performance and compliance with the test and calibration requirements.