Real-Time Measurement of Ammonia (NH₃) in Artillery Smoke Using a Passive FT-IR Remote Sensor

Early alerts for avoiding exposure to toxic chemical threats are critical applications of sensors to protect both military troops and civilian populations. Among the various sensing techniques developed, the passive Fourier transform-infrared (FT-IR) spectroscopy method has been demonstrated to work well as a remote (kilometer-scale) sensor for such early-alert systems. The passive type FT-IR detector is capable of mobile detection of toxic gas clouds because of its small-scale interferometer and optical instruments. In this article, real-time FT-IR measurements of ammonia (NH₃) in 76 mm artillery smoke are reported using a commercial remote sensor and scored by a real-time analysis conducted using a custom algorithm based on the generalized likelihood ratio test (GLRT). Using these methods, we measured the real-time change in the ammonia spectrum and GLRT scores against concrete and forest backgrounds following artillery propellant detonation. We confirmed that the GLRT score characteristics depend on the background and found that the effect of rapid heat transfer from the propellant detonation to the ammonia was detected in the accumulated ammonia FT-IR spectra.