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Catalytic recombination of dissociated atmospheric oxygen and nitrogen is a major heat source for re-entry vehicles beyond Mach 10. Present thermal protection systems are designed to the extreme assumption of full catalycity. However mass, performance, and cost considerations of future reusable launch vehicles require that their thermal protection system is designed to the more realistic assumption of partial catalycity. With this in mind, the authors of this paper have studied the catalytic behavior of a coated C/C material as it was used for the heat shield of the OREX re-entry capsule. In this presentation. we will report on the laboratory measurements of the atomic oxygen recombination coefficient and its associated coefficient for thermal accommodation. The recombination coefficient was determined in plasma test chambers by actinometry and in plasmatron at 200 and 2000 Pa, respectively. The results show an effective recombination coefficient of the order of 1% (600 K - 1900 K). Unlike Stewart and the Bruno models, we did not observe a strong temperature dependency of the effective recombination coefficient, neither in the laboratory data nor in the flight data. The observed behaviour can be explained by the Cacciatore model on silica. [ABSTRACT FROM AUTHOR]