First Characterization and Performance Evaluation of Bistatic TanDEM-X Experimental Products

TanDEM-X is an innovative bistatic and interferometric mission comprising the two twin synthetic aperture radar (SAR) satellites TerraSAR-X and TanDEM-X, which fly in a configurable close formation with the main goal to generate a global, high-accurate, and homogeneous digital elevation model (DEM) of the Earth's surface. The DEM is acquired in bistatic stripmap single polarization mode. On top of that, due to the flexibility offered by operating both satellites in different interferometric and imaging constellations, combinations of several experimental modes are possible. A dedicated science phase of the mission started in October 2014 and opened the full exploitation of such experimental modes. These unique data will support a variety of scientific remote sensing applications and will demonstrate new and innovative SAR techniques. In this paper, the expected SAR and interferometric performance of the operationally processed experimental modes available during the bistatic global DEM acquisition phase is modeled and characterized with in-orbit data. Key parameters for the determination of the quality of an SAR product, such as image resolution or noise equivalent sigma zero, or for the interferometric performance estimation, such as coherence or relative height error, are analyzed. Finally, possibilities to increase the quality of the generated DEMs are addressed.