Performance Evaluation of a Multiple-Orbit SAR interferometer

Synthetic Aperture Radar (SAR) interferometry is a promising technique for high resolution global topographic mapping. In particular, it allows one to obtain the elevation in digital format over large areas of the world. This paper presents a multiple orbit SAR interferometer simulator which uses a coherent approach based on a pulse-by-pulse synthesis, and takes account for the orbital and attitude dynamics of the space platform, the observation geometry and the sensor pointing geometry. The system parameters of the simulated spaceborne SAR system are those of ERS-I, a satellite equipped with a 30-m resolution active microwave imaging sensor. An interferogram of a homogeneous flat area is generated and, after interferometric post-processing involving image registration and two-dimensional phase unwrapping, a digital elevation model of the imaged area is carried out. A theoretical error budget on the height estimation accuracy when the radar is viewing natural, extended targets is outlined. The computed rms error on the height determination is 6 m. The results of the simulation runs show the feasibility of multiple-track SAR interferometry for terrain height evaluation, although it requires significant computational complexity.