Left: Nadir Jacobians for the HO MIRO transition at 547 GHz with respect to H₂O density. Jacobians are ploted for all velocity points as gray lines, however, several functions are plotted in color for selected velocities. This way it is easier to see which Jacobians correspond to the line wing and/or line center. Right: simulated nadir HO spectra line overlaid with vertical dashed lines of different color at certain velocities. These have correspondence to the colors and velocities shown in the left panel. In this example, the spacecraft altitude is just above 100 km from the surface. Ta stands for antenna temperature.