Analysis on the correction method of atmospheric transmittance close to the ground

Atmospheric transmittance can critically affect the accuracy of measuring infrared characteristics exhibited by targets. On the whole, the existing measurement of atmospheric transmittance has complied with the engineering calculation results of the MODTRAN software by applying several vital parameters (e.g., temperatures, air pressures and water-vapor content). In general, the error of such a method exceeds 20%, and it is significantly impacted by local weather. In this study, a ratio correction method was adopted to decrease the error in measuring atmospheric transmittance. The correction factor was determined by comparing the directly measured value from the infrared images of reference blackbody at different temperatures with the calculated value of the MODTRAN. Subsequently, the correction factor could be exploited to correct atmospheric transmittance. The experiment for measuring infrared radiation was performed, and the radiance inversion error was reduced by more than 10% after the correction of atmospheric transmittance. Furthermore, the correction factor calculated from LWIR images could be extrapolated to other bands. Besides, the inversion accuracy of the infrared radiation characteristics significantly increased. Thus, the multi-band applicability of the correction method was verified.