Future giant telescopes: Integration of MCAO into telescope design

Ground-based optical telescopes are still the fundamental tool in observational astronomy. Building future extremely large telescopes featuring AO systems is on the way with a prime goal to reach the diffraction limit in resolution with a few milliarcseconds over extended field. Current difficulties in manufacturing large deformable mirrors (DMs) limit their direct use in the main telescope system, yet it might be feasible in the future. The present paper deals with optical systems with integrated 2-3 DMs into the telescope design. Using DMs of larger diameter in the telescope, one could minimize the number of reflecting surfaces and increase the number of actuators across the DMs, hence improving throughput and reducing the AO fitting error. We present several optical designs with fully-integrated AO that provides conjugations to various heights. A comparative analysis of the imaging quality is given together with recommendations for optimal pupil diameter for each optical configuration.