Objective  Most of the new generation of surface aircraft further use stealth, power control and other means to improve their penetration ability, and their infrared radiation energy has dropped significantly, bringing more and more challenges to shipborne air defense. The medium and long wave dual-band infrared detection method effectively utilizes the different characteristics of the target radiation in the two bands to enhance the detection ability of different radiation energy areas of the surface aircraft with low characteristics at the same time.

  Methods  The infrared radiation model of an surface aircraft at different detection angles is established by using ray tracing and inverse Monte Carlo method, and the medium-long wave infrared radiation intensity of an surface aircraft at different detection angles is completed. Then, based on the calculation results of side-to-head radiation intensity, the differences of medium-long wave detection under special conditions such as rain and sea fog in the marine environment are compared and analyzed, and the medium-long wave detection data at different distances are obtained by means of the detection test of weak and small targets under the complex sea background in the actual outfield, and the equivalent temperature difference between the target and the sea background is statistically analyzed.

  Results and Discussions   The calculation results of medium and long wave infrared radiation intensity distribution of an surface aircraft at different detection angles are shown in Figure 5; The impact of sea haze, overcast rain and other weather on medium-long wave detection is shown in Figure 6 and Figure 7 respectively; The influence of sea clutter on medium and long wave detection is shown in Figure 8 and Table 2. Through the above work, the advantages and disadvantages of medium-wave and long-wave bands under different climate and sea background conditions are statistically analyzed, and the advantages of medium-wave and long-wave composite detection technology are fully verified.

  Conclusions  In sunny weather and good visibility, long-wave detection has advantages in weak and small target recognition and anti-sea clutter interference. However, in case of sea fog, rainfall conditions and poor visibility, medium-wave detection is superior to long-wave detection. Therefore, it is necessary to use the medium-long wave composite detection method to learn from each other's strong points and compensate for the weak and small target recognition probability under various sea environment conditions.