Radius of icy moons around different late-type stars with a given MO depth. The moon’s geometric albedo was set to A_g = 1.38 in each case (according to the reflectance of ice in the V photometric band), and the distance from the star is at the snowline, that is calculated from Eq. (16), and indicated in the top axis, too. Brown, blue, green and purple curves indicate the estimated photon noise levels with 5σ confidence of PLATO 2.0, CHEOPS, HST and Kepler, respectively. The dashed curves for PLATO 2.0 and Kepler indicate that these are survey missions in contrast with the HST and CHEOPS observatories. Grey vertical lines indicate the 60, 90 and 120 min MO duration contours for a moon in circular orbit around a Neptune-mass planet.