It is of strong practical significance to the management of civil aviation aircrafts through optical detection of aerial targets. A proper detection spectrum can help to enhance the target and suppress the background, guaranteeing the real-time accurate positioning and tracking of aerial targets over a wide range. Firstly, the principle of space-based air target detection is introduced. By analyzing the sources of the target radiation and background radiation, the contrast between target and background radiation intensity is determined as the evaluation standard for space-based detection. In simulations, three typical backgrounds (sea, farm and desert) and Boeing 737 aircraft were taken as examples. The apparent spectral radiance of the background in each spectral band was analyzed with the bulk and apparent spectral radiance of the aerial target under different detection conditions (detection azimuth angle, elevation angle, flight height). By traversing the 2~6 μm spectral range with a maximum spectral width of 1 μm, the contrast between target and background radiation intensity was calculated. 29 alternative spectral bands under 30 working conditions, including different flight altitudes, different backgrounds and different detection azimuth angels, were screened for the contrast between target and background radiation intensity exceeding the threshold of 2000. Considering changes in the upper and lower limit values of the contrast between the target and the background radiation intensity under each spectrum, background, target flight altitude and detection azimuth angle, the 2.53~2.54 μm spectrum could be used as one of the preferred spectral bands of the space-based aerial target optical detection system.
The broad application of hyperspectral devices makes hyperspectral image target detection a popular research. This paper presents a new method for target detection by transforming the hyperspectral data into complex networks. By analyzing the networks topological feature corresponding to each pixel, one can easily evaluate the statistical characteristics and intrinsic properties of the signals. Thereby matching the target by comparing the pixel network characteristics. The spectral characteristics of the pixel are analyzed from the perspective of the network, which provides a new spectral matching criterion. Experimental results demonstrate that the proposed method can acquire satisfactory results when compared with traditional methods.
Space based IR system uses the information of target LOS (line of sight) for target location. Recent researches show that the measuring precision of target LOS is usually determined by measuring precision of platform’s position and attitude, and deformation of sensor etc. Most methods for improving target location precision are either through improving platform’s position and attitude measuring precision or through calib rating the whole image obtained by IR sensor. With the development of measuring technology, it is harder to make a further improvement on the measuring precision of position and attitude of the platform and the expansion of the sensor view make calibrat ion of the whole image with a larger computation cost. In this paper, a method using control points to calibrate target LOS was proposed. Based on the analysis of the imaging process of the scanning sensor of space based IR system, this paper established a modify model of target LOS based on control points, used a bias filter to estimate the bias value of sensor boresight, and finally achieved the mission of target LOS calibrat ion. Different from the traditional calibration method of remote sensing image, the proposed method only made a correct ion on the LOS of suspicious target, but not established the accurate relationship between the all pixels and their real location, and has a similar calibration performance, but more lower computational complexity.
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