分布式小卫星合成孔径雷达三维地形成像的最优垂直轨迹基线
The Optimal Across-Track Baseline of Distributed Small Satellites Synthetic Aperture Radar for Terrain Elevation Measurement
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摘要: 分布式小卫星合成孔径雷达 (DSS-SAR)中垂直轨迹基线和沿轨迹基线同时存在、相互耦合，且具备多个基线，因此与单星SAR干涉相比，DSS-SAR三维地形成像最优垂直轨迹基线的确定更为复杂。该文提出了一种确定DSS-SAR三维地形成像最优垂直轨迹基线的新方法。该方法根据DSS-SAR干涉复图像对的相位差的统计特性，推导了DSS-SAR多基线干涉的干涉相位的克拉美-罗界，并由此求得测高误差与垂直轨迹基线之间的关系式，令测高误差对垂直轨迹基线的导数为零，得出DSS-SAR三维地形成像的最优垂直轨迹基线。最后根据最优垂直轨迹基线的计算式，详细分析并推导了由3颗小卫星构成的不同空间编队构形DSS-SAR的最优垂直轨迹基线，结果表明，当基线数为1时，论文推导的DSS-SAR多基线干涉最优垂直轨迹基线与已有单星SAR干涉最优基线设计结果一致。此分析结果验证了论文方法的正确性。
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关键词:
- 分布式小卫星;SAR;最优基线;编队构形
Abstract: In distributed small satellites-synthetic aperture radar (DSS-SAR), the correlation of echoes is determined by both across-track and along-track baselines which are coupling, and the multi-baseline interferometry is obtained with multi small satellites SAR images. The optimal across-track baseline of DSS-SAR for terrain elevation measurement is more complicatedly determined than that of conventional SAR interferometry. A novel approach is presented in this paper to determine the optimal across-track baseline of DSS-SAR multi-baseline interferometry. On the basis of the statistical characteristics of phase difference of complex SAR image pair, the DSS-SAR interferometric phase estimation Crammer-Rao bound is deduced. The relationship between terrain height accuracy and across-track baseline is presented from the bound. And then the optimal across-track baseline is derived via derivative calculation. Finally, the optimal across-track baseline in different DSS-SAR configuration with three small satellites is calculated and analyzed. It is showed that the optimal baseline of single across-track baseline interferometry according to this paper is in agreement with that from known single satellite SAR interferometry. The result validates the novel approach proposed by this paper. -
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