Tomographic Grid Optimization for Spaceborne Multiangle D-InSAR Tropospheric Measurements

Spaceborne multiangle differential synthetic aperture radar interferometry (SMA D-InSAR) utilizes grid-based tomography to acquire all-weather 3-D high-resolution tropospheric physical parameters. The design of the tomographic grid plays a critical role in determining the overall tomographic performance, particularly in terms of accuracy and grid size. In this letter, the impact of the tomographic grid is quantitatively analyzed, and a tomographic grid optimization method is proposed by jointly considering the grid design across different altitude layers. First, the tomographic grid-induced performance model is established to explicitly characterize the effect of grid discretization. Then, an optimization method is proposed by jointly considering grid design and observation configuration to balance the accuracy, grid size, and unretrievable grid ratio. The effectiveness of the method is validated through simulations and in-orbit experiments. Simulations show approximately 50% improvements in the three tomographic performance metrics after optimization, while the in-orbit results show high consistency between the reconstructed differential tropospheric refractivity (DTR) and external datasets, with accuracy, grid size, and unretrievable grid ratio improved by about 17%, 30%, and 25%, respectively.