13 May 2011 Passive ranging of dynamic rocket plumes using infrared and visible oxygen attenuation
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Atmospheric oxygen absorption bands in observed spectra of boost phase missiles can be used to accurately estimate range from sensor to target. One method is to compare observed values of band averaged absorption to radiative transfer models. This is most effective using bands where there is a single absorbing species. This work compares spectral attenuation of two oxygen absorption bands in the near-infrared (NIR) and visible (Vis) spectrum, centered at 762 nm and 690 nm, to passively determine range. Spectra were observed from a static test of a full-scale solid rocket motor at a 900m range. The NIR O2 band provided range estimates accurate to within 3%, while the Vis O2 band had a range error of 15%. A Falcon 9 rocket launch at an initial range of 13km was also tracked and observed for 90 seconds after ignition. The NIR O2 band provided in-flight range estimates accurate to within 2% error for the first 30 seconds of tracked observation. The Vis O2 band also provided accurate range estimates with an error of approximately 4%. Rocket plumes are expected to be significantly brighter at longer wavelengths, but absorption in the NIR band is nearly ten times stronger than the Vis band, causing saturation at shorter path lengths. An atmospheric band is considered saturated when all the in-band frequencies emitted from the rocket plume are absorbed before reaching the sensor.
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R. Anthony Vincent, R. Anthony Vincent, Michael R. Hawks, Michael R. Hawks, } "Passive ranging of dynamic rocket plumes using infrared and visible oxygen attenuation", Proc. SPIE 8052, Acquisition, Tracking, Pointing, and Laser Systems Technologies XXV, 80520D (13 May 2011); doi: 10.1117/12.883470; https://doi.org/10.1117/12.883470

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