Inversion of target radiant temperature and distance via spectrum separation

Accurate measurement of temperature and distance is essential for applications in multiple fields such as air defense, antimissile systems, laser damage, and infrared remote sensing. However, ranging currently relies on either laser or infrared radiation characteristics, neither of which fully utilize the substantial information contained in the spectrum. In this study, we realized the simultaneous inversion of target radiant temperature and distance via spectrum separation based on the distance information from the atmospheric spectrum as well as the temperature information from multispectral radiation thermometry (MRT), by measuring the thermal radiation spectrum of distant high-temperature objects. The study initially involved conducting a theoretical analysis of long-distance MRT in the atmosphere by utilizing the least squares and Newton’s iteration methods. Once the thermal radiation spectrum and the long-distance atmospheric spectral transmittance were acquired from nonlinear models, highly precise and accurate radiant temperature and distance information was derived via simultaneous inversion. Subsequently, experimental verifications were performed to measure an explosion spectrum at a temperature of approximately 2000 K and a distance of 9 km. The spectral band was 400–900 nm, and the temperature and distance of the explosion calculated by the inversion was 2004.4 K and 9.9 km, respectively. The inversion distance error was 10%, indicating that the simultaneous inversion of radiant temperature and distance was successful and that the proposed method was effective. The method proposed in this study can be applied to the measurement of radiant temperature and distance of long-distance objects.