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An expansion tube facility is operated for producing high-enthalpy flows at the nominal velocity of 8km/s relevant to Earth reentry.A semicircle edge model is exposed to the hypersonic flows.Shock wave stagnation streamline is observed along the flow direction.Spatially resolved emission spectroscopy in the wavelength range between 250nm to 550nm behind a shock wave is recorded by a spectrometer with an 1CCD camera.The experiment spectrum is dominated by the emission of CN(B2E+→X2∑+)violet band.Calibration procedure of the whole measurement system is performed and the absolute radiances of shock emissions are obtained in the corresponding wavelength region.The spectral profile of shock layer is obtained by analyzing the absolute radiance at wavelength of 384.16nm which is one of the CN peaks.And the thickness of the shock wave layer is about 4mm.Fitting with the numerical simulated spectrum of CN(B-X)violet Av=0 band,equilibrium temperature at distance of 2mm from model edge achieves to about 14000K.