Towards the Extremely Large Telescopes era in exoplanetary science: simulation tools, instrumental optimization and design for high resolution spectroscopy. The cases of ESPRESSO and ELT-HIRES.

In this thesis I present my PhD activities concerning the development of simulation tools both for ground-based high resolution spectrograph design, ESPRESSO and ELT-HIRES, and for scientific investigations in the field of exoplanetary high-dispersion transmission spectroscopy. In the ESPRESSO (the Echelle SPectrograph for Rocky Exoplanets Super Stable Observations) project, the instrument modeling through ray-tracing bsoftware and ad-hoc developed sensivity analysis tool were fruitfully used for component optimization and alignment verification. In the framework of the ELT-HIRES (the HIgh REsolution Spectrograph for the ELT) project, an End-to-End simulator and a parametric paraxial model of the spectrograph were developed with the purpose to evaluate the different effects which can affect the final instrument performances, since they directly influence the scientific data observational performances. The synthetic echellogram (raw frame) produced and successfully processed by the CRIRES+ instrument data reduction pipeline are presented, thus probing the full chain feasibility and consistency of the system. Large telescopes allowing very high contrast, could also imply the possibility to detect the light emitted from background sources and/or from gravitationally bounded companion of exoplanetary system, which could act as signal contamination. A transmission spactra simulator, a tool aimed at generating synthetic spectra, was developed and used to show that the maximum contamination occurs for background stars of G-to-M type, even though for high resolution spectra with a 4m class telescope this contamination seems to not introduce obvious shifts or line broadening in the exoplanet atmospheric features.