Image quality and high contrast improvements on VLT/NACO

TL;DR

This paper discusses recent improvements in the VLT/NACO instrument's image quality and high contrast imaging capabilities, including aberration correction and pupil tracking fixes, enhancing its performance for high contrast and coronagraphic imaging.

Contribution

It presents a comprehensive set of upgrades and calibration procedures that significantly improve NACO's image quality and contrast performance, serving as a reference for future instruments.

Findings

Successful compensation of non-common-path aberrations

Fixes to pupil tracking drift in 2011

Enhanced high contrast imaging capabilities

Abstract

NACO is the famous and versatile diffraction limited NIR imager and spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT. Since two years a substantial effort has been put in to understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in October 2011. NACO is therefore even better suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially those working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, possibly ERIS).