Active optics control and its integration with the adaptive optics in the European Solar Telescope (EST)

The European Solar Telescope (EST) is a 4-m class solar telescope that will include a Multiconjugate Adaptive Optics system (MCAO) integrated in the telescope optical path. Its open-dome configuration implies that the complete telescope will be exposed to wind, having an important impact in image stability and quality. The integration of Active Optics (AcO) and adaptive optics (AO) in solar telescopes represents a pivotal area of research aimed at enhancing solar observation capabilities. This study delves into the convergence of these two factors. On one hand, the AcO, responsible for real-time adjustments in optical components such as mirrors, to compensate for mechanical deformations and misalignments. On the other one, the AO, designed to counteract atmospheric turbulence and enhance solar image resolution. Diverse strategies are explored for merging these systems, leveraging advancements in high-sensitivity wavefront sensors, advanced control algorithms, and adaptive deformable mirror configurations. AcO will be in charge of mitigate the low frequency- huge distortions, as gravitational and thermal deformations and the quasi-static component of wind and AO will be in charge of high frequency-small distortions, as wind buffeting and atmospheric turbulences. An analysis of the different strategies proposed for control of the AcO loop and its planned actuation ranges is presented in this paper.