Total flux F, the linearly polarized fluxes Q and U, and the degree of polarization P of the spatially unresolved, edge-on, baseline planet–moon system, as functions of the planet’s phase angle α_p. Also included are curves for the isolated planet (coinciding with Q and U of the planet–moon system) and the isolated moon (equal to zero in Q, U, and P). Fluxes have been normalized such that at α_p= 0°, F equals the geometric albedo of the planet–moon system or each of the isolated bodies. The labels in the plot for F refer to the illustrations in Fig. 6.