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Ground-based infrared imaging tracking system (GIITS) is of great importance for aerial target
warning and guard. The operating range is one of the key performance specifications, which should be
calculated, analyzed and studied during the whole GIITS design process. The operating range is mostly
influenced by a few factors, including atmospheric attenuation, the performance of GIITS and feature of
target and background. This paper firstly makes analysis and summarization on the definite localizations of
the traditional operating range equation of the GIITS. The localizations are mainly in two aspects. On one
hand, the dispersion of the image and the effect of image dispersion are not considered in the traditional
method; on the other, calculate the radiation power received on the detector in order to analysis whether the
output signal meets the detection requirements or not, without considering the effect of the background
radiation. By improving of the traditional method, a new operating range calculation model of the GIITS
was established based on two requirements. One is that the image size of observed target should meet the
requirement of the processor signal extraction. The number of the pixel occupied by target image should be
more than 9. The other is that the signal noise ratio (SNR) of the GIITS should not be less than 5 to meet
the requirements of the target detection probability and spatial frequency. The SNR calculation equation in
form of energy is deduced and the radiation characteristic of the observed target and background are
analyzed. When evaluate the operating range of the GIITS using the new method, we should successively
calculate two operating range values according to two requirements mentioned above and choose the
minimum value as the analytic result. In the end, an evaluation of operating range for fighter aircraft is
accomplished as an example. The influence factors in every aspect on operating range were explored by the
calculated result. The new operating range calculation model provides the theoretical basis for the design
and applications as well as the comprehensive evaluation of a GIITS.
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