German Earth-observation satellite. The twin to its predecessor TerraSAR-X, it launched on 21 June 2010 from the Baikonur Cosmodrome aboard a Dnepar-1 rocket. TanDEM-X was placed in a near-*polar orbit where it flys in close formation with TerraSAR-X, only a few hundred metres apart; the two satellites image the Earth simultaneously, from different angles. These images are processed into accurate elevation maps with a 12-metre resolution and a vertical accuracy better than 2 metres. Like the TerraSAR-X mission, TanDEM-X is a project developed under a public–private partnership between the German Aerospace Center (DLR) and Astrium GmbH based in Friedrichshafen, Germany.