German radar satellites fly tight space waltz

Two German radar satellites are now flying in tight formation as they prepare to make the most detailed ever 3D map of the Earth's entire surface.

TanDEM-X and TerraSAR-X have moved to within 350m of each other as they sweep around the planet at 7km/s.

The pair will soon begin an intense observation campaign that will pin down the variation in height across the globe to an accuracy of better than two metres