A tunable diode laser absorption spectroscopy sensor and a high-speed camera measuring narrow-band emission are deployed at the NASA Langley Hypersonic Materials Environmental Test System, a hypervelocity arc-heated tunnel. Both sensors target electronically-excited atomic oxygen. The sensors are used in conjunction to measure bulk translational temperatures (from 500 to 3000 K) and number densities of the \(^5S_2\) excited state of atomic oxygen (from near 0 to \(5\times 10^{16}\) m \(^{-3}\) ) in the arc-heated freestream at arc currents ranging from 100 to 250 Amperes, and with varying feed-gas mixtures composed of diatomic oxygen, diatomic nitrogen, and argon. Additionally, spatially-resolved diode laser absorption measurements of the same atomic oxygen energy-state population are collected near a silicon carbide test sample via an inverse Abel transform. Significant temporal flow transients are detected in the freestream on a 60-Hz timescale. These transients also propagate into the near-model shock layer. Further, qualitative agreement is obtained between absorption- and emission-based sensors. This study provides a quantitative, spatiotemporally-resolved dataset for future comparisons to computational models of the facility flowfield. The study also represents the first deployment of tunable diode laser absorption spectroscopy sensors in the Hypersonic Materials Environmental Test System.
