Abstract: Aiming at the issue of aircraft infrared camouflage, the relationship between the infrared contrast and the operating range of an infrared system was deduced, an approximate expression for the relation between the atmospheric transmittance and operating range was obtained through exponential fitting, and a simplified method of calculating the operating range was developed. The influences of major factors on infrared contrast and operating range, such as the target external temperature, the infra-red (IR) emissivity of the target, and the flight speed, were also studied by theoretical analysis. The results show that infrared contrast and operating range exhibit basically the same trend of being lowered by decreasing the target temperature, emissivity, and flight speed. Under certain conditions, infrared contrast could take the place of operating range to serve as a convenient parameter for predicting the infrared camouflage effect of an aircraft. The infrared camouflage of an aircraft would have better effect with smaller infrared contrast. The rapidity, accuracy, flexibility and large application scope of infrared contrast calculation provide certain theoretical reference for further study on infrared-camouflage of aircraft.

Key words: infra-red camouflage, evaluation, aircraft, infrared contrast, operating range