Abstract. The post-flight analysis of a space mission requires an accurate determination of the free-stream conditions for the trajectory. Quantities such as the atmospheric temperature and density conditions can be rebuilt from the heat flux and pressure measured on the spacecraft. The rebuilding methodology requires a cross-fertilization of results obtained from experiences and interpretation gained via numerical simulations. Knowing that experimental data suffer from errors, this methodology also needs to integrate quantification of uncertainties. Epistemic uncertainties on the chemistry models in the bulk and at the wall (surface catalysis) are taken into account. Rebuilding the free stream conditions from flight data amounts to solving a stochastic inverse problem. We use experimental data obtained at the von Karman Institute in high enthalpy ground facilities to validate the simulation tools and improve our understanding of physical phenomena. In turn, the extrapolation of ground experiments to flights conditions will allow for prediction of the free stream properties in flight with their associated uncertainty.