Adaptive Optics for Extremely Large Telescopes

Adaptive Optics has become a key technology for the largest ground-based telescopes currently under or close to begin of construction. Adaptive optics is an indispensable component and has basically only one task, that is to operate the telescope at its maximum angular resolution, without optical degradations resulting from atmospheric seeing. Based on three decades of experience using adaptive optics usually as an add-on component, all extremely large telescopes and their instrumentation are designed for diffraction limited observations from the very beginning. This review illuminates the various approaches of the Extremely Large Telescope, the Giant Magellan Telescope, and the Thirty-Meter Telescope, to fully integrate adaptive optics in their designs. The article concludes with a brief look into the requirements that high-contrast imaging poses on adaptive optics.