Together with the almost identical TerraSAR-X satellite, which has been operational since 2007, TanDEM-X will generate a digital elevation model of the Earth's landmasses in unprecedented quality over the course of three years. For this purpose, TanDEM-X and TerraSAR-X form a radar interferometer: The satellites fly in close formation at a distance of only a few hundred metres, thus enabling simultaneous terrain images from different perspectives. The two satellites are scheduled to measure the complete land surface of the Earth (150 million square kilometres). For a 12-metre grid (street width), height information can be determined with an accuracy of less than two metres.
IABG has conducted extensive tests to prove the satellite's suitability for operation in space. The testing programme covered electromagnetic compatibility, thermal-vacuum tests including sun simulation, vibration tests, acoustic tests and the determination of the satellite's mass properties. A special feature during the test campaign was the so-called 'Boom-Release Test' investigating the shock loads in the satellite which were caused by unfolding its antenna in space. The qualification tests were conducted at IABG’s space centre in Ottobrunn, one of the ESA-coordinated test centres.
The PPP agreement between Astrium and DLR defines TanDEM-X funding and data utilisation. Thus, the partners jointly finance the satellite at a total cost of approximately €85 million: € 59 million will be provided by DLR and €26 million by Astrium. Furthermore, DLR develops the mission-relevant ground segment and is responsible for mission planning and implementation, as well as for the control of both satellites and the generation of the digital elevation model. Data exploitation for scientific purposes is coordinated by the DLR institute for high-frequency technology and radar systems. Infoterra GmbH (Friedrichshafen), a wholly owned subsidiary of Astrium, is exclusively responsible for the adaptation of the elevation model to the needs of commercial users and for its world-wide marketing.
The decisive advantage of satellite-based Earth measurement is the generation of a globally consistent and homogeneous elevation model with no discontinuity at regional or national borders and no inhomogeneities resulting from different measurement procedures and measurement campaigns staggered in time. The radar plays a decisive role here, since it can be operated completely independent of weather and clouds, day and night.
This mapping procedure is currently unparalleled and is of particular interest to the USA. TanDEM-X is a key project for demonstrating, safeguarding and extending Germany’s competence and competitiveness in the field of satellite-based radar technology.
Germany will possess a digital elevation model of the Earth – a unique data product – which, in addition to many scientific application possibilities, can be used by organisations such as the DLR centre for satellite-based crisis information (ZKI - Zentrum für satellitengestützte Kriseninformation) and by programmes and initiatives, such as GMES (Global Monitoring for Environment and Security), GEOSS (Global Earth Observation System of Systems), and also in security-relevant cooperation agreements.
Similar to TerraSAR-X, the 'sister satellite' of TanDEM-X, the commercial exploitation of data and derived products is part of the PPP agreement between Astrium and DLR. Infoterra GmbH, an Astrium subsidiary, founded in 2001 for commercial TerraSAR-X marketing, will also be responsible for providing new TanDEM-X-based height information to its customers all over the world.
Since the commencement of TerraSAR-X's operational service in early 2008, Infoterra has been able to establish a solid position on the global market for Earth observation data and services and has set up a distribution network with more than 50 partners in 33 countries. This promising business basis will also be used to successfully market the TanDEM-X data and products.
The fields of application are versatile and range from an increased efficiency in the production of oil, gas or minerals, improved crisis mission planning, prediction of the impacts of disaster situations to a more specific preparation of defence and security missions. First and foremost, in many countries all over the world, cartographers will be able to obtain improved height information – thanks to this more precise and current data source.