TanDEM-X - Land Survey from Space
* Mapping of the Earth with innovative radar interferometer
* High-precision digital elevation model available as of 2010
* Project financing in a public-private partnership
Berlin, ILA 2006, 16 May 2006
Innovation in the field of geodesy, i.e. the measurement of the Earth, has a long tradition in Germany. With the new TanDEM-X satellite, the German Aerospace Centre (DLR) and Europe's leading satellite manufacturer, EADS Astrium in Friedrichshafen, want to open a new chapter in 'Earth measurement'.
The measurement of the Earth was already a matter of great importance to the famous natural scientist, Alexander von Humboldt, who pursued this aim with simple means during his long exploring expeditions. Of course, the technologies used today, such as photogrammetry, enable a more precise, faster, and – as a result of being airborne – an easier measurement of large, regional areas.
Furthermore, the potential for Earth measurement from space has already been proved in several missions, such as the ERS1/ERS2 tandem and the radar mission with the US space shuttle SRTM. The achieved precision, however, was clearly below that of terrestrial and airborne procedures. This gap will now be closed by the German TanDEM-X satellite mission.
The engineers of EADS Astrium in Friedrichshafen have now started the construction of the TanDEM-X satellite. Its launch into orbit is planned for the year 2009. Together with the almost identical radar satellite TerraSAR-X which is to be launched in autumn 2006, it will form a high-precision radar interferometer.
With the aid of the tandem formation TerraSAR-X/TanDEM-X it will be possible to completely measure the Earth's land surface, that is 150 million square kilometres, within a period of only 2.5 years. The resolution of the generated digital elevation model will correspond to that of the existing airborne procedures: For a 12m grid (street width), height information can be determined with an accuracy of < 2 meters.
The decisive advantage of a satellite-based Earth measurement is the generation of a world-wide, consistent and homogeneous terrain model with no discontinuity at regional or national borders and no inhomogeneities resulting from different measurement procedures and measurement campaigns staggered in time (mosaics). The radar plays a decisive role here, since it can be operated completely independent of weather and light conditions.
At present, the procedure is unparalleled and receives particular attention in the USA. TanDEM-X is a key project for demonstrating, safeguarding and extending the German competence and competitiveness in the field of satellite-based radar technology.
Like TerraSAR-X, the TanDEM-X project will be carried out within the scope of a public-private partnership between EADS Astrium GmbH and the German Aerospace Centre (DLR). It settles the utilisation of data for scientific purposes under the management of the DLR institute for microwave systems and for commercial purposes, for which Infoterra GmbH (Friedrichshafen), a subsidiary of EADS Astrium GmbH, is exclusively responsible.
The provision of industrial investments for the implementation of this mission significantly eases the public sector's financial burden, and as far as the amount of public and industrial funds is concerned, the TanDEM-X mission is an extremely cost-effective and economic commitment. The industry's partial financing will be amortised on the basis of the business plan. In the case of a positive result of the commercialisation effort, additional profit can be made, which is then available for the further development of technologies and applications in the field of radar-based Earth observation.
Digital terrain models are of vital importance for numerous scientific and commercial applications. Precise and current information on the Earth's surface and its topography represents an important basis for almost all geo-scientific areas, such as hydrology, glaciology, geology, forestry and environmental sciences.
Furthermore, digital terrain models are the prerequisite for a reliable navigation, in particular with regard to navigation systems, such as GNSS and Galileo, which are also subject to further development. In addition to the generation of digital terrain models, the two satellites allow the execution of selective velocity measurements both of extremely slow motions (flow of glaciers) and of very fast motions (road traffic). These measurement procedures are to be tested scientifically/experimentally and are to open up future operational applications. The international team of scientists for TanDEM-X comprises about 100 renowned representatives of different geo-scientific areas and experts in the field of radar technology and methods. Fifty per cent of the scientists are from German universities and research institutes.
The outstanding cost-performance ratio of the TerraSAR-X / TanDEM-X satellites will allow the offering of terrain models at a much lower price than with the current procedures. There is already a worldwide demand from national mapping agencies in rising countries with a poor mapping status, and from intelligence organisations of the EU, NATO, G7, MGCP, etc., which increasingly use the data of commercial providers.
As of 2010, Germany will possess a digital terrain model of the Earth – an attractive and worldwide unique data product – which can be used in initiatives and programmes, such as the centre for satellite-based crisis information (ZKI - Zentrum für satellitengestützte Kriseninformation), GMES (Global Monitoring for Environment and Security) and GEOSS (Global Earth Observation System of Systems), and also in security-relevant cooperation agreements.
From the technical point of view, the satellite-based radar interferometer is based on three major elements:
• The two satellites TerraSAR-X and TanDEM-X must fly in very close and configurable formation. Their distance will be adjusted as required between a few kilometres and 200 metres. Additionally, the two satellites will circle each other in the course of one Earth orbit. The collision-free flight of these satellites is an interesting challenge which will be met by the specialists of the GSOC (German Space Operations Centre, Oberpfaffenhofen).
• As is the case with all interferometers, it is decisive to know the exact 'eye distance' of the two sensors employed – in this case, the radar instruments on the satellites TerraSAR-X and TanDEM-X. This distance measurement is based on a sophisticated evaluation of the GPS signals received by each of the two satellites. In the formation flight described above, the scientists of the geo-research centre in Potsdam, (GFZ - GeoForschungszentrum Potsdam under the management of Prof. Rothacher) will be able to determine the baseline with an accuracy of approx. 1mm.
• The third important element is the exact temporal synchronisation of the two radar instruments. For this purpose, pulse-shaped signals are sent form one satellite to the other. They allow the coordination of radar imaging within a period of microseconds. The bi-static operation of our radar interferometer which is achieved in this way, is unique worldwide and of great importance for the outstanding accuracy of the system.
All technologies required for the mission have already been investigated and tested, therefore the technical risks can be considered as minor and manageable.
TanDEM-X - a programme of significant importance and great benefit for the German space technology: Technology, scientific and commercial applications of radar-based Earth observation will substantially be reinforced. All the existing German commitments in the field of radar-based Earth observation have been successful, have considerably improved the international competitiveness of German space technology and are the result of a consequent focus within the national space programme.
EADS Astrium is Europe’s leading satellite system specialist. Its activities cover complete civil and military telecommunications and Earth observation systems, science and navigation programmes, and all spacecraft avionics and equipment.
EADS Astrium is a subsidiary of EADS SPACE. In 2005 EADS SPACE had a turnover of €2.7 billion and 11,000 employees in France, Germany, the United Kingdom and Spain.
EADS is a global leader in aerospace, defence and related services. In 2005, EADS generated revenues of €34.2 billion and employed a workforce of more than 113,000.
Contacts for the media
Rémi ROLAND
EADS SPACE
(FR)
Tel.: +33 1 42 24 27 37
Jeremy CLOSE
EADS SPACE
(UK)
Tel.: +44 1438 773872
Mathias Pikelj
EADS SPACE
(GER)
Tel.: +49 7545 8 9123
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