A study of the scintillation effects on the point-spread function (PSF) halo of the high-contrast imaging instrument (Characterization of Exoplanets by Opto-Infrared Polarimetry and Spectroscopy [CHEOPS]) for direct exoplanet detection from the ground is presented. The fundamental goal of our analysis is to quantify the perturbations induced by the amplitude (scintillation) variations compared with those induced by the phase variations of a perturbed wave front. Simulations of amplitude and phase screens are obtained for different seeing conditions and for a wave front propagating at different zenith angles. For all cases, a set of simulations of the PSFs in the ideal mirror-limited case (perfect wave front sensor and adaptive optics system) and an estimation of the detection limit Δm versus angular separation obtained with and without scintillation are presented. The whole study is made in the I band (λ = 0.9 μm), i.e., the centered wavelength of the CHEOPS polarimetric imager. A maximum loss of contrast (obtained with and without scintillation) of ~25% over a field of view of 5'' is found in the speckle noise-limited regime, and ~18% in the photon noise-limited regime. Results are discussed, and conditions in which the scintillation effects cannot be neglected are investigated.
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