At high angular velocity, the signal-to-noise ratio(SNR) of star image may become very low due to star point tailing, which leads to the decline of the star extraction rate. To solve this problem, an adaptive star extraction algorithm is proposed in this paper. Firstly, the star image is divided into several blocks, and the adaptive global threshold method is used in each block to get the gray extremum of each block. Then, the weight matrix of the star under the current angular velocity is obtained adaptively by Kalman filter. For the selected extreme pixel, the background threshold of the pixel is obtained by using the maximum background estimation method according to the calculated weight matrix. Finally, region growth is carried out in the eight neighborhood of the current pixel until all the star pixels are extracted. The experimental results show that this algorithm can extract stars in images taken at high angular velocity, and the extraction rate is higher than that of the traditional scanning method, which proves the algorithm is effective and has good robustness.
The polarization of infrared radiation is an important characterization of the feature and state information of the space object’s surface. Due to the different in materials, surface features and on-orbit states, the polarization provides a theoretical support for the detection and recognition of the space targets. Through the detecting the polarization, the dimension of the target information would be increased, and then the ability of detection and recognition to the target would be increased too, so the shortcomings of the traditional infrared detection would be compensated. In this paper, the overall polarization characteristics from the reflection and self-radiation of the object are studied, and a mathematical model of the infrared polarization characteristics is established based on the bidirectional reflectance distribution function. And the influence of the surface roughness, the viewing angle and the zenith angle of incidence is analyzed on the degree of polarization. The research in this paper may provide basic theoretical support for infrared polarization detection and identification of space objects.
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