Light curve extracted from a CHEOPSim image time series, using photometric extraction performed by the data reduction pipeline that will be used with real CHEOPS data, for planet GJ 1214b (radius 2.68R_⊕, orbital period 1.58 days), orbiting the star GJ 1214 (V = 15.1, spectral type M4.5V). The exposure duration is 60 s and exposures are not stacked. Gaps in the light curve correspond to interruptions due to Earth occultation (once per CHEOPS orbit). The simulated photon flux from the target star incident on the telescope, with stellar granulation as the only noise source, is shown by the red line. The transit depth from the photometric extraction is diluted due to the presence of a contaminant background star within the photometric aperture (radius 33 pixels), visible in the example image shown on the right.