Preliminary design of the MICADO calibration unit

MICADO is the Multi-AO Imaging Camera for Deep Observations, which aims to be the first light instrument of E-ELT. Thanks to its robust design with fixed mirrors and a cryogenic environment, MICADO will provide unprecedented astrometric capabilities and image stability in the range 0.8-2.4 μm. The operation of the instrument coupled with a SCAO unit provides diffraction-limited images over a field of view of 27” that will enlarge to 53” after the integration of the Multi-conjugate Adaptive Optics RelaY, MAORY. This work presents some preliminary possible concepts for the MICADO calibration unit, currently under development at MPIA. This subsystem shall provide standard flat-fielding and spectral calibration plus an astrometric calibration performed with an internal calibration mask to measure and compensate instrument distortions, discontinuities between the detectors and telescope instabilities. The goal of the instrument is to deliver an astrometric accuracy of ~50 μas over the whole field of view.