The sky coverage calculated as in Sect. 6.2 for the 0.5–2 keV (top panel) and 2–10 keV (bottom panel) band. The solid lines represent the sky coverages evaluated with the baseline model (i.e. power-law spectra with Γ = 1.8 absorbed by Galactic N_H = 3.3 × 10²⁰ cm^-2). The dotted lines represent the sky coverages for power-law spectra with Γ = 1.4 absorbed by Galactic N_H = 10²² cm^-2. The short-dashed lines represent the sky coverages for power-law spectra with Γ = 1.8 absorbed by N_H = 10²² cm^-2. The long-dashed lines represent the sky coverages for power-law spectra with Γ = 1.4 absorbed by N_H = 3.3 × 10²⁰ cm^-2.