A Radiometric Calibration and Error Analysis Method for HWRS SAR at S-band
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摘要: 合成孔径雷达(SAR)系统的辐射定标可以构建SAR图像与地物后向散射截面积(RCS)的关系，反演目标物理特性，满足SAR定量化遥感需求。相对于其它波段，S波段SAR的定量化遥感工作罕见报道。该文利用已知SAR及平台参数进行S波段SAR辐射定标处理，首先推得了图像像素值与目标后向散射系数的关系，接下来详细分析了各项误差对定标精度的影响，给出了天线指向误差对定标精度影响的解析表达式。该文的分析有利于建立各参数与辐射定标精度的关系，方便设计时候的误差分配。该文给出了草地、道路和平静水面的S波段后向散射截面积统计值。最终实际数据处理结果表明，该系统利用该定标方法可以在20°的视角范围内实现较高的绝对辐射精度。Abstract: The radiometric calibration of Synthetic Aperture Radar (SAR) can establish a mapping relationship between SAR image and Radar Cross Section (RCS) of ground objects, which benefits the inversion of target physical properties, and further meets the needs of quantitative remote sensing. Compared with other wavebands, the reports about SAR works in S-band are rare. This paper focuses on the radiometric calibration of radar at S-band by using the known parameters of radar and plane. Firstly, the relationship between image pixel intensity and RCS of target is derived. Then, a detailed analysis on each error component is implemented, in which, the affection of antenna direction on radiometric calibration precision is given by the analytic expression. The analysis and simulation is propitious to error allocation during the design period. In addition, the mean RCS statistics of grass, road and calm water are given. The real data processing results show that a sufficient accuracy in 20° view angle can be achieved by using the radiometric calibration method.
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表 1 雷达及飞行参数表
参数 数值 平均功率(W) 19.2 距离范围(m) 3450～6250 视角范围(°) 48～70 采样频率(MHz) 400 波长(m) 0.09375 距离采样间隔(m) 0.375 接收机增益(dB) 67 飞机速度(m/s) 70 
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表 2 定标器RCS测量结果(dB)
像素值 绝对辐射精度 定标图 检验图 定标图 检验图 1°误差图 T1 128.8 128.2 20.5 19.9 18.7 T2 128.4 128.4 20.1 20.0 19.0 T3 128.4 128.7 20.1 20.3 19.3 T4 128.9 129.3 20.6 21.0 20.1 T5 129.1 129.5 20.8 21.2 20.9 T6 129.1 129.4 20.8 21.0 21.4 T7 128.9 129.0 20.6 20.6 22.0 T8 128.6 128.6 20.3 20.2 21.9 T9 128.3 128.7 20.0 20.3 22.7 T10 128.3 128.6 20.0 20.2 22.4
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