Multi baseline SAR acquisition concepts and phase unwrapping algorithms for the TanDEM-X mission

The TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) mission will start in 2009 with the aim of generating a global Digital Elevation Model with high accuracy corresponding to HRTI-3 specifications (12 m posting, 2 m relative point-to-point height accuracy for flat terrain). To achieve this goal, a second satellite similar to TerraSAR-X will fly close to TerraSAR-X in a controlled Helix configuration for 3 years to jointly acquire interferometric SAR data in bistatic mode. According to the current mission concept, there will be at least two complete coverages of the global land surface, each one running one year. The different coverages will have different heights of ambiguity to allow multi-baseline phase unwrapping. For the sake of a homogenous data quality the second acquisition will be shifted by half the swath width with respect to the first coverage. Finally difficult terrain will be covered two more times with different acquisition geometries (i.e. different look direction and/or incidence angles). This paper presents first study results of phase unwrapping algorithms foreseen to process SAR data from the bistatic TanDEM-X configuration.