A method is presented for determining the dependence of the probability of heterogeneous recombination "/to from results of measurements of the heat fluz Qto to the surface of a catalytic sensor exposed to a pulsed supersonic flow of gas dissociated by an incident shock wave propagating in a shock tube. It is shown that the accuracy of the determination of 7to depends not only on the accuracy of the measurements in the ezperiment, but also on the results of mathematical modeling of the flow of the dissociated gas over the surface of the body. Results from an analysis of an experiment are presented.Introduction. The catalytic properties of materials in relation to heterogeneous recombination in supersonic flows of dissociated gases have a significant effect on the level of thermal loads on a body in such a flow [1]. In connection with the development of the "Shuttle" and "Burns" reusable spacecraft, the 1980s marked the beginning of extensive experimental and theoretical research to determine the basic regularities of the processes occurring on a surface in heterogeneous catalytic reactions and the quantitative characteristics of these reactions for different materials [2][3][4][5][6]. The effect of the state of the gas interacting with the surface on the probability of heterogeneous recombination "Yw is still unknown. Of the known experimental methods, the method that most closely approaches conditions that arise when bodies enter the dense atmospheric layers involves determination of 7,# by exposing a model to a pulsed supersonic flow of a gas that has been dissociated by an incident shock wave propagating in a shock tube [7]. The only measurement in these experiments is the one of the heat flux Qw to the surface of the test material, which depends on the catalytic heterogeneous reactions that occur and on the processes that take place in the gas layer over the surface. Thus, the accuracy of the determination of 7,, depends not only on the accuracy of measurement of heat flux Qto but also on the results of mathematical modeling of the flow of dissociated gas over the surface of the body.In this paper, we present results of determining the probability of heterogeneous recombination of oxygen atoms from the experimental data of [8, 9]. We use laminar boundary layer theory as the mathematical model and allow for the nonequilibrium of the chemical reactions and multi-component diffusion [1]. The initial equations are solved by a highly efficient numerical algorithm characterized by a high order of accuracy [10]. The algorithm does not require preliminary solution of the Stefan-Maxwell relations for diffusion flows. The calculations were performed for different sets of conditions in the incoming flow, and the efficiency and accuracy of the algorithm were evaluated. Approximation solutions of the given problem were obtained in [11, 12] with simplifying assumptions on the character of the gas flow in the boundary layer.Formulation of the Problem. We are examining a hypersonic nonequilibrium flow of a mixture of 02, O...