Four simulated transit light curves generated by PRISM. The observational wavelength of the simulated transits was 785 nm. These were generated using a 3.0 R_⊕ sub-Neptune planet transiting a 3700 K, 0.493 R_⊙ M1V dwarf star with i = 90.0° and P = 2 d. The starspotproperties were set at θ = 0°, ϕ = 90° and T_spot = 3475 K. The rms scatter of the light curves from left to right are 60, 100, 150, and 200 ppm. Each light curve shows the smallest detectable starspot size for the scenarios, 0.017R_* (red), 0.026R_* (blue), 0.035R_* (green), and 0.044R_* (purple), which increases with increasing noise. The solid lines represents the noise-free synthetic light curves containing the starspotanomaly, while the filled circles represent the spot-free synthetic light curves (see Sect. 3) with added Gaussian noise.