Abstract: The radiative energy emitted and absorbed by high temperature gas in the shock layer must be considered in the thermal protection system design of hypervelocity vehicles. Efficient evaluation methods are needed to predict the radiative heat flux. Absolute radiance measurement in ground facilities is an important way to understand the physics of the high enthalpy flow and to improve the numerical models. Radiance calibration techniques have been developed in a combustion-driven shock tube. High resolution spectral radiative intensities have been measured in rich N₂ environment to validate the numerical models. Detailed radiance spectral structures have been acquired at shock velocity 5.70 and 6.20km/s. It is found that the non-equilibrium process behind the shock affects the gas radiation remarkably. Numerical simulations under corresponding experimental conditions have been conducted using an in-house built code solving Navier-Stokes equations with chemical reaction models and radiation models. The results show that computational results agree well with experimental data.