The TanDEM-X-Mission (TerraSAR-X add-on for Digital Elevation Measurement) is based on two nearly identical Earth observation satellites, TerraSAR-X and TanDEM-X. Both are equipped with modern, efficient synthetic aperture radar systems (SAR) with which the surface of the Earth can be observed independently of daylight and cloud cover. TerraSAR-X has already been launched in 2007; TanDEM-X followed at June 21, 2010. From then on, the two satellites are flying in formation for three years on their 514-kilometre orbit, maintaining a distance of a few hundred metres. During that time, they will generate a unique high-resolution 3-D elevation model of the entire land surface of the Earth.
The TanDEM-X project consistently builds on former national and international radar missions such as X-SAR and SRTM as well as on the successful implementation of the national TerraSAR-X project. DLR is in charge of the project and mission management, the ground segment, and the operation of the satellite.