Variation spectrum as planet/star contrast (left) and S/N (right). These plots give the peak amplitude of the phase variation as a function of wavelength. The orbital distance of the planet is 0.02 AU, its radius 2 R_⊕, and its inclination 60°. Each curve is for a given stellar mass. To calculate the S/N, we set Δλ = 1 μm, distance = 10 pc, telescope diameter = 1.5 m. The gray area corresponds to the 5−15 μm range (left & right) and to contrasts higher than 10^-5 (left).