Calibration of NAOS and CONICA static aberrations

Application of the phase diversity technique

¹ Office National d'Études et de Recherches Aérospatiales, Département d'Optique Théorique et Appliquée, BP 72, 92322 Châtillon Cedex, France e-mail: laurent.mugnier@onera.fr
² Laboratoire des Signaux et Systèmes, École Supérieure d'Électricité, Plateau de Moulon, 91192 Gif-sur-Yvette, France
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Corresponding author: T. Fusco, thierry.fusco@onera.fr

Received: 16 July 2002
Accepted: 25 October 2002

Abstract

We describe and evaluate the performance of a phase diversity wavefront sensor used to measure the static aberrations of the VLT instrument NAOS–CONICA. The main limitations of this phase diversity technique are compiled. We investigate the systematic errors due to the experimental implementation and the design restrictions. Further error sources stem from the imperfect knowledge of the system, and from limitations of the algorithm. The influence of these errors on the wavefront estimation is evaluated on numerical and experimental data. This study highlights the essential verifications and calibrations needed to obtain accurate results and gives a practical guideline for the application of a phase diversity wavefront sensor. The comprehensive calibration results and the final gain in optical performance are presented and discussed in a complementary paper ([CITE]).