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 a Neptune-sized planet orbiting a V = 12 K5V star with a 13 day orbital period. 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 incident on the telescope is shown by the red line. Stellar granulation was not simulated, resulting in a smooth curve.