The χ² maps of the 5 September 2019 event. Panels a and b: The and maps, respectively. The denotes the goodness-of-fit only using observational data, while denotes the goodness-of-flt with the additional a priori information represented as the χ² type value, (Δ_ρ/σ_ρ)². These maps are used to derive the best-fitting atmospheric pressure p₀ at the reference radius r₀ of 1215 km and the cross-track correction Δρ to the ephemerides, of which the a priori uncertainty σ_ρ is 72 km. The surface pressure p_surf and the geocentric closest approach distance ρ_cag to the shadow center are obtained by linear transformations of Δρ and p₀, respectively. The best-fitting and values per degree of freedom are 1.160 and 1.155, respectively.