Example light curve (left) and stellar disc (right) generated by PRISM. Light curve: the solid line represents the noise-free synthetic light curve containing the starspot anomaly, while, the filled circles represent the spot-free synthetic light curve (see Sect. 3) with added Gaussian noise. Stellar disc: the central solid line represents the stellar equator (assuming orbital alignment) and the upper and lower solid linesrepresent the upper and lower boundaries of the transit cord. These were generated with a 1.5 R_⊕ super-Earth planet transiting a 3200 K, 0.155 R_⊙ M4V dwarf star with i = 90.0° and P = 1 d. The starspotproperties are: θ = 0°, ϕ = 90°, r_spot = 0.035R_* and T_spot = 3000 K. The observational wavelength and rms scatter for the simulated data were set at 785 nm and 150 ± 7.5 ppm, respectively.