The MICADO first light imager for ELT: cold optics instrument

MICADO, the Multi-AO-Imaging-Camera and Spectrometer for Deep Observations, is one of the first light instruments for the future 40 m class Extremely Large Telescope (ELT). MICADO utilizes the advanced laser guide star multiconjugate adaptive optics system MCAO developed by the MAORY consortium and the jointly developed singleconjugate adaptive optics system (SCAO). We present an overview on the conceptual design of the MICADO Cold Optical Instrument (COI) which comprises the infrared focal plane imager with its 3 x 3 4k 2 HgCdTe detector array and a compact cross-dispersing slit spectrometer operating in the spectral range of 0.8 to 2.4 μm. High contrast imaging is enabled via a classical configuration of coronagraph and Lyot stops. The paper summarizes the MICADO COI interchangeable optics, its cryogenic implementation together with the modular opto-mechanical configuration of the cryo-mechanisms and the cryo-vacuum cooling system, which consists of a continuous LN2 flow cryostat.