Simulating the optical alignment of the multiconjugate adaptive optics module for the extremely large telescope

Adaptive optics (AO) instruments for the future extremely large telescopes (ELTs) are characterized by advanced optical systems with diffraction-limited optical quality. Low geometric distortion is also crucial for high accuracy astrometric applications. Optical alignment of such systems is a crucial step of the instrument integration. Due to relative inaccessibility of these giant instruments, automatic alignment methods are also favored to improve the instrument availability after major events, such as extraordinary maintenance. The proposed alignment concept for these systems is described: the notable example which is analyzed here is the case of the multiconjugate AO relay for the future ELT. The results of ray-tracing simulations carried out to validate the method are discussed in detail, covering the error sources, which could degrade the alignment performance.