Infrared Surveillance Alarm Equipment Operating Distance Equivalent Conversion Method Research

The IR warning-reconnaissance system which is one of key components of the Electro-optical countermeasure equipment is always employed for reconnoitring, identifying and giving warning of approaching threats such as aircrafts and missles. Besides, it is aslo used to indicate accurate direction of the threats and give leading information for Electro-optical countermeasures. The most important performance index of IR warning-reconnaissance systems is operating distance which has been usually assessed by flying tests in open fields. However, this method can only evaluate operating distance on some typical weather conditions. It is necessary to find a practical method to evaluate the index on different weather conditions.This paper focuses on the demands of the tests and assessments of the operating distance of IR warning-reconnaissance systems in test fields. Firstly, the methods of image filters and the development of nine-templates judge criteria are putting forward in the weak and tiny target image process, and the infrared radiations are calculated using the calibration coefficients which were obtained in real tests calibrating. Subsequently, the influences of atmospheric IR radiation transmittance attenuations, the path radiations, the atmospheric background radiations in tiny target images and the radiations of optical system are analyzed theoretically to find the equivalent calculation methods between the targets surface radiances and the image grey levels. Then the influences of temperature, humidity, visibility, pressure, azimuth and elevation on the sky background radiations and atmospheric transmittance are calculated using the atmospheric radiations and transmittance calculating codes, after that the equivalent calculation equations are presented. Finally, the programs for equivalent calculations of IR images are compiled which are subsequently used for real flying tests images. By the way of the digital image injecting tests, the equivalent images are injected into the IR warning-reconnaissance system through the I/O instrument to estimate the operating distance which is compared with the field test results. Based on those works, the equivalent calculations of operating distance of IR warning-reconnaissance systems on different weather conditions for the same targets and their flight routes are realized.The works of this paper which develop the methods of operating distance evaluating of IR warning-reconnaissance systems will be applied in the filed tests to reduce the costs. Moreover, it will be helpful for the tactical applications of IR warning-reconnaissance systems.