The ground seg­ment

The ground segment, which was originally developed by a DLR team for TerraSAR-X, was extended for the TanDEM-X mission to accommodate the operation of two satellites. It also has extensive features such as safe formation flying, precise baseline determination, and a high-performance data reception and processing chain. Additional specific features were added for TanDEM-X operations.

A key issue in operating the missions jointly is the different image acquisition scenarios. While TerraSAR-X requests are typically for single scenes that will be used by individual scientific and commercial customers, the global digital elevation model requires a global mapping strategy. This strategy has to also account for the formation geometry in use at any given time, which, in turn, depends on the helix parameters selected. This is because any given helix permits the acquisition of digital elevation model data only within a certain range of latitudes.

In addition, the two satellites are available for individual use during the three-year tandem phase. For this purpose, a reference mission scenario was developed under which first priority is accorded to digital elevation model images. This scenario leaves enough space for planning TerraSAR-X images around those taken by TanDEM-X.