TanDEM-X is a challenging radar mission. It consists of a synthetic aperture radar interferometer with two almost identical satellites flying in a closely controlled formation. With a typical separation between the satellites of 120 to 500 m a global Digital Elevation Model (DEM) with 2 m relative height accuracy at 12 m posting is being generated. While the main mission phase for DEM data acquisition has been finished by mid-2014, the processing of the global TanDEM-X DEM will be concluded by mid-2016. Final DEMs for Australia, large parts of North America, South America, Africa and Siberia are already available for scientific and commercial applications. The results achieved so far are well within the expected performance for the global DEM. A 15-month science phase of the TanDEM-X mission started in October 2014 which offers the opportunity to generate DEMs with even higher accuracy for selected areas, and to explore and demonstrate the new scientific applications of this unique mission.