The German Radar Missions TerraSAR-X and TanDEM-X

Abstract

TerraSAR-X is Germany’s first national remote sensing satellite that has been implemented in a public-private partnership between the German Aerospace Center (DLR) and EADS Astrium GmbH, with a significant financial participation from the industrial partner. It will supply highquality radar data for purposes of scientific observation of the Earth for a period of at least five years. At the same time it is designed to satisfy the steadily growing demand of the private sector for remote sensing data in the commercial market. The TerraSAR-X satellite was successfully launched from the Russian spaceport Baikonur on June 15th, 2007. Shortly after, the commissioning of the satellite and the radar instrument could be completed according to schedule thus enabling TerraSAR-X to start its operational service at the beginning of 2008. Since then the satellite and the instrument have proven their extraordinary performance in many cases. Many thousand data takes were successfully acquired and further processed into image products, the quality of which often significantly exceeds the original requirements. The high stability of the sensor, the high precision of calibration as well as the extremely good position accuracy must be emphasized. The first image could be presented in record time four days after launch, since then the mission can be characterized by its smooth operation and production process. TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) opens a new era in space borne radar remote sensing. A single-pass SAR-interferometer with adjustable baselines in across- and in along-track directions is formed by adding a second (TDX), almost identical spacecraft, to TerraSAR-X (TSX) and flying the two satellites in a closely controlled formation. TDX has SAR system parameters which are fully compatible with TSX, allowing not only independent operation from TSX in a mono-static mode, but also synchronized operation (e.g. in a bi-static mode). With typical across-track baselines of 200-400m DEMs with 2 m relative height accuracy at a 12 m posting will be generated. The HELIX concept provides a save solution for the close formation flight with vertical separation of the two satellites over the poles and adjustable horizontal baselines at the ascending/descending node crossings. DEMs are of fundamental importance for a broad range of scientific and commercial applications. For example, many geoscience areas like hydrology, glaciology, forestry, geology, oceanography and land environment require precise and up-to-date information about the Earth’s surface and its topography. Digital maps are also a prerequisite for reliable navigation, and improvements in their precision needs to keep step with the advances in global positioning systems. This contribution presents the status and results of the TerraSAR-X mission whose original objectives will be continuously pursued as well as the profile and status of the TanDEM-X mission.