Temperature Measurements of the Air Plasma Flow Using Optical Emission Spectroscopy

The rotational temperature of the freestream flow generated by the Scirocco arcjet plasma wind-tunnel facility of the Italian Aerospace Research Center (CIRA) is measured by means of optical emission spectroscopy. The gas mixture used to perform the atmospheric reentry simulation tests is air, and the optical spectrum emitted 17 cmaway from the exit section of the nozzle has been investigated over the 220–310 nm wavelength range. The optical setup is based on a 1200-grooves=mmmonochromator and a 1024 256 charge-coupled device camera, and the spectrum has been calibrated using a combined deuterium–halogen radiation source. The rotational temperature is determined by comparing the experimental spectra with those obtained by the spectral simulation software LIFBASE 2.0. A pattern-matching algorithm is used. Attention is mainly focused on the NO emission bands, and partial agreement between experimental results and numerical predictions is achieved for six test campaigns conducted in the arcjet facility. Finally, an error analysis has been performed to assess the error bands of the measures.