Interferometric SAR Processing: From TerraSAR-X to TanDEM-X

Abstract:
In 2009, the German radar satellite TerraSAR-X will be supplemented with its twin; the TanDEM-X satellite. Together, they will fulfil the primary TanDEM-X mission goal of deriving a global Digital Elevation Model (DEM) with an unprecedented accuracy corresponding to HRTI-3 specifications (2 m relative point-to-point height accuracy for moderate terrain at 12 m posting). First interferometric processing results from TerraSAR-X repeat-pass acquisitions impressively demonstrate the DEM accuracy that can be achieved from such high resolution X band data. They also confirm the suitability of the phase preserving focussing algorithms, the successful migration of the InSAR algorithms from SRTM to the new challenging TerraSAR-X domain (requiring e.g. terrain dependent co-registration) and the stability of the instrument. This paper outlines the planned SAR data workflow from screening over bistatic focussing and interferometric processing to raw DEM generation. It addresses some aspects of the SAR processing algorithm which exploits the synergies of bistatic focussing and interferometric processing parameter calculation. Intermediate complex image products are introduced. Emphasis is laid on required co-registration accuracy and multi-baseline phase unwrapping and DEM reconstruction algorithms foreseen for the TanDEM-X data processing.