Filtered Image Thermography for High Temperatures in Hypersonic Preheated Ablation Experiments

Thermography for measuring high temperatures, ranging from 1000 to 2900 K, in hypersonic preheated ablation experiments is demonstrated in this work. Filtered images at different wavelengths were acquired to obtain temperature maps by two methods: dual-wavelength signal ratio and multiwavelength Planck fit. This technique was applied for temperature measurements of resistively heated graphite ablators used in ablation experiments performed in the X2 super-orbital expansion tube at The University of Queensland, Australia. Six different narrow band pass filters with center wavelengths of 450, 500, 600, 700, 800, and 900 nm housed in a motorized filter wheel, coupled to a camera, were used in this work. The dual-wavelength method involves acquiring optical images of the target with two different optical filters, and the signal ratio between those two images was used to calculate the temperature map. The multiwavelength method uses more than two filtered images, from the signals of which a temperature map was...