Last Thursday, the two German radar satellites of the TanDEM-X formation finally reached their operational orbit configuration, with only a few hundred metres separating them. In this configuration, they act as a unique radar interferometer in space. The next day, on Friday evening, the instruments were switched on, after many careful checks, to acquire the world's first Digital Elevation Model (DEM) data using a free-flying bistatic Synthetic Aperture Radar (SAR) satellite formation. That same night, the jointly acquired data were received and processed by our operational processing chain.