MAORY: wavefront sensor prototype and instrument optical design

MAORY will be the multi-conjugate adaptive optics module for the ELT first light. Its main goal is to feed the high-resolution NIR imager and spectrograph MICADO. The present Thesis address the MAORY system at the level of optical design and analysis. MAORY is a complex science projects whose stakeholder is the scientific community. Its requirements are driven by the science cases which request high resolution and astrometric accuracy. In an ideal world without atmospheric turbulence, MAORY optics must deliver diffraction-limited images with very low optical distortions. The tolerance process is one of the most important step in the instrument design since it is intended to ensure that MAORY requested performances are satisfied when the final assembled instrument is operative. The baseline is to operate wavefront sensing using six sodium Laser Guide Stars and three Natural Guide Stars to solve intrinsic limitations of artificial sources and to mitigate the impact of the sodium layer structure and variability. The implementation of a laboratory Prototype for Laser Guide Star wavefront sensor at the beginning of the phase study of MAORY has been indispensable to consolidate the choice of the baseline of wavefront sensing technique. The first part of this Thesis describes the results obtained with the Prototype for Laser Guide Star wavefront sensor under different working conditions. The second part describes the logic behind the tolerance analysis at the level of MAORY optical design starting from definition of quantitative figures of merit for requirements and ending with estimation of MAORY performances perturbed by opto-mechanical tolerances. The sensitivity analysis on opto-mechanical tolerance of MAORY is also a crucial step to plan the alignment concept that concludes the arguments addressed by this Thesis.