Highlights of the design of an ELT-class calibration unit for MCAO systems

Abstract

The sheer size of the ELT, makes almost every aspect of the design of its instrumentation particularly challenging. Instrument size typically increases with telescope size, together with the need to have a larger number of wavefront sensors in advanced MCAO systems. To calibrate novel AO modules with multiple WFSs, complex opto-mechanical subsystems are needed to project on the telescope focal plane a large number of high-quality artificial light sources at different wavelengths, both LGS and NGS. These calibration units play a crucial role not only during operations, but also during the Assembly, Integration, Test and Verification phase. Moreover, the increasing size, technical complexity and costs require to develop new design solutions that make use of custom devices and photonic technologies. This work will focus on the design of the MORFEO-CU, a prime example of calibration unit for MCAO systems in the ELT era.