星载SAR辐射定标及其精度分析

随着星载合成孔径雷达（SAR)应用需求的发展，为了观测目标的物理特征，可以利用辐射定标技术获取更加精确的目标后向散射系数信息。主要完成单通道单极化条带成像模式下辐射定标及其精度分析，首先从雷达方程出发，进行严格的数学推导研究单通道单极化条带模式辐射定标技术；其次给出通过对已知雷达散射截面积的目标的观测，得到SAR图像上的灰度值与绝对的雷达散射截面积之间的关系；采用测量定标常数的方法，并基于辐射定标流程建立辐射精度误差模型和计算公式，重点研究了短期相对定标和长期相对定标中各因素对精度的影响。而且针对定标常数对绝对定标精度的影响给出了详细说明，指出星载SAR系统需要定期地完成系统修正。最后以TerraSAR-X卫星为例进行了计算验证，结果表明辐射精度预估值与实测值相差小于0.05 dB。

Radiometric Calibration and Accuracy Analysis based on Spaceborne SAR

With the development of spaceborne synthetic aperture radar(SAR)application,the radiometric calibration technology was used to observe objects′ physical characters. Because the radiometric calibration technology is very complex,on the study of radiometric calibration and accuracy analysis will be mostly focused in the strip mode with single channel and single polarization.Firstly,the radar equation was derivated,then with the measured calibration constant,the short-term and long-term relative calibrations were studied based on an error model and formula. At the same time,the influence of calibration constant for absolute radiometric precision was analyzed and the system correct was finished.Finally the validated result on TerraSAR-X satellite shows that the difference of the calculated value and the measured one is less than 0.05dB.