Laboratory Testing the Layer Oriented Wavefront Sensor for the Multiconjugate Adaptive optics Demonstrator

TL;DR

This paper reports laboratory tests of the Layer Oriented Wavefront Sensor for the MAD system, demonstrating its ability to measure phase screens at different altitudes for adaptive optics correction.

Contribution

It presents the first laboratory validation of the Layer Oriented Wavefront Sensor's capabilities for multiconjugate adaptive optics.

Findings

LO WFS can measure phase screens at multiple altitudes.

The sensor successfully aligned and integrated before delivery.

It can detect up to 8 reference stars within a 2 arcmin field.

Abstract

The Multiconjugate Adaptive optics Demonstrator (MAD) for ESO-Very Large Telescopes (VLT) will demonstrate on sky the MultiConjugate Adaptive Optics (MCAO) technique. In this paper the laboratory tests relative to the first preliminary acceptance in Europe of the Layer Oriented (LO) Wavefront Sensor (WFS) for MAD will be described: the capabilities of the LO approach have been checked and the ability of the WFS to measure phase screens positioned at different altitudes has been experimented. The LO WFS was opto-mechanically integrated and aligned in INAF - Astrophysical Observatory of Arcetri before the delivering to ESO (Garching) to be installed on the final optical bench. The LO WFS looks for up to 8 reference stars on a 2arcmin Field of View and up to 8 pyramids can be positioned where the focal spot images of the reference stars form, splitting the light in four beams. Then two objectives conjugated at different altitudes simultaneously produce a quadruple pupil image of each reference star.