Total (top) and polarized (bottom) flux curves at various noise levels. The number of photons that represents a total flux equal to 1.0 (a white Lambertian planet at α = 0°) is N_max; the range of N_max used for the polarized flux differs from that used for the total flux, because the former is generally smaller than the latter (cf. Fig. 7) and thus more sensitive to noise. The curves labeled “no noise” (N_max = ∞) are sine functions with similar amplitudes as the curves in Fig. 7.