Differential Tropospheric Tomography Using Spaceborne Simultaneous Multiangle D-InSAR: Method, Optimization, and Performance Analysis

Spaceborne synthetic aperture radar differential interferometry (D-InSAR) can measure large-scale surface deformation. When the deformation is negligible, the interferometric phase can be used to estimate the differential tropospheric delay (DTD). Nevertheless, a single satellite can only obtain the integrated DTD along the line-of-sight direction. Spaceborne simultaneous multiangle synthetic aperture radar (SSMA-SAR) observes a scene by multiangle spaceborne SAR satellites at the same time. It can measure integrated DTD from different viewing angles by D-InSAR, which will help realize the tomographic inversion of differential tropospheric refractivity (DTR) to obtain its spatial 3-D distribution. However, the inversion performance is sensitive to phase errors in interferograms, troposphere conditions, and system configurations. To address these issues, this article establishes an SSMA-SAR tropospheric tomography model, analyzes the error sources in the inversion, and proposes an optimization configuration design method for SSMA-SAR tropospheric tomography based on the nondominated sorting genetic algorithm II (NSGA-II). The simulation results show that SSMA-SAR has good potential to achieve high-accuracy 3-D DTR, with more than 70% improvement with the optimized configuration. Within the north latitude range of 0°-55°, the system can obtain high-precision 3-D DTR measurements and achieves submillimeter integrated tropospheric delay accuracy in the zenith direction with subkilometer resolution.