The MICADO first light imager for the ELT: Sparse Aperture Masks, design and simulations

Abstract: MICADO, the European Extremely Large Telescope first light imager will feature a dedicated high contrast imaging mode specifically designed for observing and characterizing exoplanets and circumstellar disks. Two sparse aperture masks (SAM) will be included, consisting of opaque masks with a set of holes arranged in a non-redundant configuration. Pupil masking transforms a monolithic telescope into an interferometer, with the aim of recovering spatial information down to the diffraction limit of the telescope and below, even in the presence of residual aberrations, such as turbulent AO residuals, and non common path aberrations. On the ELT, SAM will enable the detection of features down to 3.3mas in the J band, 12mas in the K band. Two designs have been chosen and will be reviewed, with complementarity in terms of sensitivity and spatial frequency coverage for image reconstruction. In this contribution, the technical choices will be detailed, such as the hole diameter and arrangement, given the technical constraints such as spectral filter bandwidths, detector dimensions, sampling, read-out-noise and frame rate. We will also report on simulations performed to assess the expected capabilities of this mode, with application examples of close companion detection and contrast curves.