In the Shock Wave Research Center, Institute of Fluid Science, Tohoku University, a streak camera system has been used to study high-speed phenomena associated with hypervelocity flow conditions. In the different facilities available, including the expansion tube, different test conditions can be produced for the study of the shock layer around bodies. In certain extreme conditions, the flow is in non-equilibrium and the radiation inside the shock layer is strong enough to be measured by existing spectroscopic techniques. Analysis of the spectra can provide information on the properties of the gas and can be used to validate numerical models. In the present study, time-resolved spectroscopy has been carried out in order to investigate the useful test time of the expansion tube, a very important parameter in the process of calibration of this facility. A spectroscopic system consisting of an Action Research spectrograph of 500 mm focal length, a streak unit (Hamamatsu Photonics) and a CCD camera has been used to measure time-resolved spectra down to microsecond time scales. The system is also equipped with a lens-coupled intensifier of high dynamic range.