Adaptive Optics Facility
ASSIST

The Adaptive Optics Facility (AOF) Test Bench: ASSIST

It is intended to test thoroughly, in Europe, all the systems composing the AO Facility before delivery in Paranal. The AOD is convinced that this strategy was a key-element to the success of the commissioning of the first generation AO modules delivered by AOD.

ASSIST is developed by the University of Leiden (PI: Remko Stuik) in the framework of a collaboration between ESO-CRAL-University of Leiden. CRAL (Observatoire de Lyon) is the leading institute of the MUSE consortium and the University of Leiden is part of it. The contribution of the University of Leiden to the MUSE project is to produce the Test Bench ASSIST.

However, in the case of the AOF such strategy implies a serious challenge, the main one being how to design a Test Bench allowing the implementation of a 1.1 convex aspheric deformable mirror in the optical path !!! An ingenious solution was found by optical designer B. Delabre (ESO) and is now used as a baseline by the ASSIST developer tems in Leiden.

Requirements
Opto-Mechanical Design
Functionalities & Role
Development Team

Requirements

ASSIST must provide a long and sophisticated list of functionalities:

Use the DSM 1.1m convex mirror in the optical path
provide a f/15 Nasmyth-like opto-mechanical I/F for the output focal plane
provide a large FOV (4 arcmin)
provide high optical quality at 2 wavelengths: 589 nm (laser beam) and 1.6 micron (scientific corrected wavelength)
low pupil distortion (to insure a good match between actuator geometry on the DSM and the WFS apertures distribution)
provide laser and natural light sources at the input focal plane, of variable intensity
simulate turbulent wavefront in the whole field of view affected by a multi-layered turbulence at a level of 0.6 to 1.1" seeing
be operated by a simple soft. GUI

Optical and Mechanical Design

The fundamental problem is that in order to test a 1.1m convex piece of optics, one needs an optical component > 1.1m. It already implies that the test setup will require a large volume and meter-telescope size optical components.

The Figure 1 shows this optical design. The component "AM1" is the main mirror and is a concave aspheric surface of 1.7m diameter. The is the heart of the test bench. A second smaller aspheric mirror (140mm diameter) is located above , just below the surface of the DSM. Beamsplitters/mirrors will allow to fold the beam on the side for the input and output focal planes.

Figure 1: ASSIST Optical Design

The mechanical implementation take the form shown on Figure 2.

Opto-Mecha.

Figure 2: Opto-Mechanical Implementation of ASSIST.

ASSIST ROLE & Functions

The following list describes the test and characterization processes that will take place and that ASSIST will allow to perform:

Optical Tests of the DSM
Setup and Alignment of the AO modules
DSM Flattening, measure of the Influence Functions, characterization of the mirror stroke
Interaction Matrix measurement and loop closure
Investigation of the various IM calibration methods proposed and evaluation of their performance
Chopping tests, Field Stabilization tests, focusing
Mounting of test cameras for delivered image correction
Pupil alignment and study of Command Matrix for GLAO and LTAO
LGS and Visible/IR NGS acquisition
AO performance optimization

Development Team

ASSIST Development Team
Project Manager & PI	Remko Stuik	stuik@strw.leidenuniv.nl
Optics	Pascal Hallibert	hallibert@mail.strw.leidenuniv.nl
ESO contact	Stefan Stroebele	sstroebe@eso.org

For more details on ASSIST design and the developer team see the following links:

Adaptive Optics Facility ASSIST