TanDEM-X: The New Global DEM Takes Shape

TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is an innovative formation flying radar mission that opens a new era in spaceborne radar remote sensing. The primary objective is the acquisition of a global Digital Elevation Model (DEM) with unprecedented accuracy (12 m horizontal resolution and 2 m relative height accuracy). This goal is achieved by extending the TerraSAR-X synthetic aperture radar (SAR) mission by a second, TerraSAR-X like satellite TanDEM-X (TDX) flying in close formation with TerraSAR-X (TSX). The resulting large single-pass SAR interferometer features flexible baseline selection enabling the acquisition of highly accurate cross-track interferograms not impacted by temporal decorrelation and atmospheric disturbances. Beyond the global DEM, several secondary mission objectives based on alongtrack interferometry as well as new bistatic and multistatic SAR techniques have been defined. Since 2010 both satellites have been operated in close formation to map all land surfaces at least twice and difficult terrain even up to four times. While data acquisition for DEM generation will be concluded in the second half of 2014 it is expected to complete the processing of the global DEM by the end of 2015. This paper provides an overview of the TanDEM-X mission and summarizes its actual status as well as the performance of the system and the first final DEMs. Up to now the mission driver was the DEM generation and scientific experiments have been limited to the pre-defined DEM formation geometries. This paper also outlines the current planning for a dedicated science phase starting in the last quarter of this year.