Signal attenuation ratio (f) as a function of column density from the calculations of Debout et al. (2016). Plain symbols are for the H₂O ν₃ band, with the column density scale given in the bottom x-axis. Open symbols are for the CO₂ν₃ band, with the column density scale given in the top x-axis. Calculations correspond to an azimut of 45°, a phase angle of 90°, a heliocentric distance of 2 AU, and isotropic gas production with total H₂O and CO₂ production rates of 10²⁷ and 8 × 10²⁵ s^-1, respectively. The highest column densities correspond to altitudes of 0.2, 0.5, 0.8, 1.0, 1.50, 2.0, 3.0 km, with the column density decreasing with increasing altitude.