基于亚像素图像平移叠加提高大倾角同步卫星信噪比的方法研究

Research on Improving SNR of Large Angle Synchronous Satellite Based on Sub-pixel Translation and Superposition

大倾角地球同步轨道(GEO)卫星相对地面并非完全静止,其星下点做南北方向的“8”字周期运动,倾角越大运动范围越大.这会降低地面望远镜对其进行凝视观测时的有效曝光时间,无法获得较高的信噪比.对地球同步轨道的监测中,在硬件条件不变的前提下,提出亚像素图像平移叠加方法.根据目标的运动速度和相邻帧图像的时间间隔,在亚像素尺度平移并对齐多幅图像,使GEO目标星象在图像序列中的位置重合,通过叠加多幅序列图像来提高目标信噪比,从而达到提升整个系统探测能力的目的.实测图像叠加结果表明,该方法可以显著提高该类目标的信噪比.叠加5幅图像时,整数像素叠加图像的信噪比约为原图像的1.7倍,而亚像素叠加图像的信噪比是原图像的2倍左右.

Geosynchronous satellite with big inclination is not completely stationary relative to the ground.Its sub-satellite point moves periodically in the north-south direction with ground track of shape like“8”.The larger the inclination angle is,the larger the range of motion is.Such effect makes the effective exposure time of Geosynchronous satellite limited when observe it by optical telescope with stare mode,and the SNR(Signal Noise Ratio)of Geosynchronous satellite image could not be increased with long exposure time.In the monitoring of Geosynchronous orbit without changing hardware,a method called sub-pixel translating superposition of successive frames of images is proposed.By translating and aligning images in the sub-pixel scale according to the moving speed of the object and the time interval of the adjacent frame images,the positions of the Geosynchronous satellite in the image sequences are coincident,and then by superposition of these translational images,the SNR of moving Geosynchronous objects and the detection capability of the whole system can be improved.Results of superposition of real observed images show that the method can remarkably improve the SNR of moving.When five images are superimposed,compared with the SNR of the original image,the SNR of the superimposed image by integer pixels is increased by around 1.7 times,and the SNR of the superimposed image by sub-pixel is increased by about 2 times.