Modeling the MIRI detector pixel integration ramps using Poisson_CCD. Top left: signal distribution in the MIRI imager PSF in 1D versus the Poisson_CCD simulated PSF (2D Gaussian). Both PSFs are centered on the x-axis using their respective centroids. Top right: MIRI imager raw ramps (solid colored curves) and ramps from the Poisson_CCD simulation output (dotted lines). The frame number in the case of the Poisson_CCD simulation corresponds to how many times N = 45 000 tracers have been added to the simulation. To compute the DN level for the simulated pixels, the number of electrons that reached each pixel in each simulation step was divided by the pixel gain of 5.5 e⁻ DN⁻¹. For visualization purposes, we offset the Poisson_CCD vertically by 2000 DNs. Bottom left: subsequent frame differences as a function of time (frame number). Bottom right: subsequent frame difference as a function of the pixel absolute DN level. The vertical black line shows the saturation limit.