<p>A method of parametric identification of a set of thermophysical characteristics (specific thermal conductivity, specific heat capacity, integral reflectivity and emissivity) of high-enthalpy thermally decomposable thermal protection under Joule heating in diffusion approximation is proposed. The problem of finding the extremum of the mean-square functional of the residual between the theoretical and experimental temperature fields at the locations of temperature sensors is solved with preliminary specifications of the basis functions that take into account the dependence of the characteristics under consideration on temperature. Optimization of the thermal protection parameters is performed using the conjugate gradient method as the most accurate algorithm of the first order of convergence. For its implementation, three conjugate heat exchange problems are preliminarily solved to determine the sensitivity coefficients necessary to calculate the gradient of the residual functional under study.</p>