The highly precise determination of the relative position (baseline) between the two radar satellites TerraSAR-X (since 2007) and TanDEM-X (since 2010) is crucial for the quality of the interferometric SAR data (InSAR) used to create the resulting digital elevation models (DEMs). Even the smallest errors in the baseline determination can influence the DEM accuracy and lead to height errors in the mapped surface structures.

Section 1.2 calculates these baselines using state-of-the-art software that combines measurements from both satellites. In particular, observations from the two dual-frequency GPS receivers provided by GFZ for both missions are used for this purpose. The low orbit height (approx. 500 km) and the small relative distance of only a few hundred meters between the satellites pose a particular challenge. Nevertheless, the achieved precision is in the millimetre range.

By combining various baseline solutions, such as those of the GSOC (German Space Operations Center) of the DLR (German Aerospace Center), which are calculated using different software packages and approaches, GFZ also creates an optimised baseline with the highest accuracy and minimal residual errors. The calculated baselines are transferred to the DLR as daily products for further processing of DEMs. In this context, GFZ is also actively involved in international research networks to continuously further develop the methods of baseline determination and to keep them always up to date with the latest technology.

Project partners:

• DLR (German Aerospace Center, Oberpfaffenhofen, Germany)

Project duration:

• Since 2010

Funding:

• DLR (German Aerospace Center, Oberpfaffenhofen, Germany)