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International audience; HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes- SCAO (including a High Contrast capability) and LTAOor with NOAO. The project is preparing for Final Design Reviews. The high-contrast module (HCM) has been designed to characterize planets as close as 100mas from their host star (goal: 50mas), and presenting a 1e-6 f lux ratio with it. To do so, it will use (1) a passive atmospheric dispersion corrector, (2) a set of amplitude apodizers and focal plane masks to lower the di↵racted intensity next to the star and attenuate the PSF core, (3) a dedicated Zernike wavefront sensor to track the non-common path aberrations with the SCAO subsystem at a 0.1Hz frequency, and (4) post-processing algorithms that will rely on the temporal and spectral diversity of the IFS data to separate the planetary signals from the noise. This communication details several trade-o↵ analyses involved in the co-design of the hardware of the HCM. It also presents contrast performance estimates that have been derived through an analysis of post-processed, simulated IFS data obtained with an end-to-end numerical model of the HCM and the rest of HARMONI. The respective interests of ADI and molecular mapping are compared in this specific case.

ELT-HARMONI is the first light visible and near-IR integral field spectrograph (IFS) for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews. The High Contrast Module (HCM) will allow HARMONI to perform direct imaging and spectral analysis of exoplanets up to one million times fainter than their host star. Quasi-static aberrations are a limiting factor and must be calibrated as close as possible to the focal plane masks to reach the specified contrast. A Zernike sensor for Extremely Low-level Differential Aberrations (ZELDA) will be used in real-time and closed-loop operation at 0.1Hz frequency for this purpose. Unlike a Shack-Hartmann, the ZELDA wavefront sensor is sensitive to Island and low-wind effects. The ZELDA sensor has already been tested on VLT-SPHERE and will be used in other instruments. Our objective is to adapt this sensor to the specific case of HARMONI. A ZELDA prototype is being both simulated and experimentally tested at IPAG. Its nanometric precision has first been checked in 2020 in the case of slowly evolving, small wavefront errors, and without dispersion nor turbulence residuals. On this experimental basis, we address the performance of the sensor under realistic operational conditions including residuals, mis-centring, dispersion, sensitivity, etc. Atmospheric refraction residuals were introduced by the use of a prism, and turbulence was introduced by a spatial light modulator which is also used to minimise wavefront residuals in a closed loop in the observing conditions expected with HARMONI., 14 pages, 13 figures, SPIE Astronomical Telescopes + Instrumentation (AS22)