Active optics strategy for the alignment and operation of the European Solar Telescope

Belío-Asin, M.; Sánchez-Capuchino, J.; Mato, A.; González-Cava, J. M.; Cozar-Castellano, J.; Soler, M.; Ferro, I.; Núñez Cagigal, M.; Barreto, M.
Bibliographical reference

Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series

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The European Solar Telescope (EST) is an on-axis 4.2-meter solar telescope, the largest solar telescope ever built in Europe. While operating, environmental effects, such as gravity, wind buffeting or thermal loads, will generate wavefront errors that require to be corrected. For this reason, the EST team is developing an active optics strategy to ensure that quasi-static aberrations resulting from optical misalignments are minimised and that the remaining residual errors are small enough to maintain the image quality requirements. A hexapod, with five degrees of freedom (tilt, centring and focus), will be mounted on the secondary mirror to actively control the position of M2 and provide the proper alignment of the telescope. This contribution outlines the step-by-step analysis of the active optics system developed to establish the procedure to be implemented in EST. The sensitivity matrix, obtained from the optical model, that will be needed for adjustments during operation is shown. In addition to the optical elements that will be involved during the strategy, as well as their particular movements, the effects of these adjustments and the final residuals that will remain, ensuring a seeinglimited performance.