Example of a χ²(Δρ, p_surf) map derived from the simultaneous fit to the light curves obtained during the 2016 July 19 occultation. The quantity Δρ is the ephemeris offset of Pluto (expressed in kilometers) perpendicular to its apparent motion, as projected in the sky plane. The other parameter (p_surf) is the surface pressure of the DO15 atmospheric model. The white dot marks the best fit, where the minimum value of χ² is reached. The value , using 4432 data points, indicates a satisfactory fit with a χ² per degree offreedom of 4716/4432 ~ 1.06. The best fit corresponds to p_surf = 12.04 ± 0.41 μbar (1-σ level). The error bar is derived from the 1-σ curve that delineates the level. The 3-σ level curve (corresponding to the level) is alsoshown.