Adaptive optics simulations for the MICADO SCAO system

We present in this paper the current simulation results of the single-conjugate adaptive optics (SCAO) mode of the wide-field imager MICADO. MICADO is a near-IR camera for the European ELT, featuring a wide field (75"), spectroscopic, and coronagraphic capabilities. It has been chosen by ESO as one of the two first-light instruments. MICADO will be optimized for the multi-conjugate adaptive optics module MAORY and will also work in SCAO mode. This SCAO mode will provide MICADO a high-level, on-axis correction, making use of the adaptive secondary M4 in the telescope. It is shown here that the on-axis compensation level reaches Strehl ratios (SR) of the order of 0.70 in K band under median seeing condition, and quickly degrades with field angle. However, despite the important leak of the light from the core towards the halo, we demonstrate how the point spread function (PSF) remains topped with an Airy-like pattern even at low SR below 0.02. This known effect, due to the large telescope aperture, was already shown in past studies. We show here how dependent from the outer scale value this effect is, and we study how the presence of this peak allows the instrument to preserve astrometric capabilities even far out of the isoplanatic patch domain.