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TerraSAR-X - Germany's radar eye in space



TerraSAR-X is a German Earth-observation satellite. Its primary payload is an X-band radar sensor with a range of different modes of operation, allowing it to record images with different swath widths, resolutions and polarisations. TerraSAR-X thus offers space-based observation capabilities that were previously unavailable. The objective of the mission is to provide value-added SAR (Synthetic Aperture Radar) data in the X-band, for research and development purposes as well as scientific and commercial applications.

The successful launch of TerraSAR-X on 15 June 2007 at 08:14 local time from the Russian Baikonur Cosmodrome in Kazakhstan marked the start of a campaign to map the Earth at an unprecedented level of accuracy. The aim is to create new, high-quality radar images of the Earth’s surface over the next five years.

Night and overcast conditions are no problem for TerraSAR-X

 German radar satellite TerraSAR-X
zum Bild German radar satellite TerraSAR-X

The satellite is in a near-polar orbit around the Earth, at an altitude of 514 kilometres. Using its active radar antenna, it is able to produce image data with a resolution of down to one metre, regardless of weather conditions, cloud cover or absence of daylight. TerraSAR-X has been fully operational since 7 January 2008. Every part of this satellite was built in a very compact way. It has a five-metre-long body with a hexagonal cross section and its primary payload is an active radar system. The radar beam can be electronically tilted within a range of 20 to 60 degrees perpendicular to the flight direction, without having to move the satellite itself. This has an obvious advantage: it allows the radar to zoom in on many more ground targets from the satellite’s orbit than would be possible using a 'non-steerable' radar.

The TerraSAR-X mission is carried out under what is known as a public-private partnership between the German Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung; BMBF), the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and Astrium GmbH. The total cost of manufacturing and launching the satellite amounted to 130 million euro. DLR paid 102 million euro, and space technology company Astrium contributed 28 million euro from its own funds. Developing the ground segment and operating the satellite over a five-year period adds another 55 million euro to the total costs. DLR is contributing 45 million euro, the remaining 10 million are being provided by Infoterra, a wholly-owned subsidiary of Astrium, created specifically for commercial data marketing.

Germany - world leader in Earth observation

DLR is responsible for the scientific usage of the data, and it takes care of designing and implementing the mission and of controlling the satellite. Registered users can search online through all the available data in DLR's EOWEB catalogue (see the link in the right-hand column). If they submit their project proposals to DLR, scientists can receive TerraSAR-X data. For this service, they are only charged the data reproduction costs. Data for commercial use is sold through Infoterra GmbH. The satellite’s total data-collecting capacity will be divided equally between science and industry.

TerraSAR-X builds on the technology and insight gained in earlier radar missions, and allows systematic observations to be conducted over a longer period of time. Observing vegetation, for instance, is exceptionally relevant for human life. Accurate and up-to-date information about the distribution and composition of, and changes in, types of vegetation forms the basis for many applications. One of the things that makes TerraSAR-X stand out is its high spatial resolution, surpassing what was previously possible using civilian radar systems. This enables scientists to examine detailed ground features, for instance the differentiation between different crops, in order to arrive at an improved classification of ground use.

TerraSAR-X at a glance: 

Length: 4.88 metres
Diameter: 2.4 metres
Launch mass: 1230 kilograms
Payload mass: about 400 kilograms
Radar frequency: 9.65 Gigahertz
Power consumption: 800 watt (on average)
Resolution: 1 metre, 3 metres, or 16 metres
(depending on the image size)
Launch vehicle: Dnepr 1 (converted SS-18)
Launch date: 15 June 2007, 4:14 CEST
Launch site: Baikonur, Kazakhstan
Orbital altitude: 514 kilometres
Angle of inclination with respect to the equator: 97.4 degrees (Sun synchronous)
Mission life time: at least 5 years

 Satellite mission TanDEM-X
zum Bild Satellite mission TanDEM-X

Germany is already advancing even further: TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), a second, almost identical satellite, is scheduled for launch before the end of 2009. It will be brought to the same orbit as TerraSAR-X. This satellite will also be manufactured under a public-private partnership. TanDEM-X is expected to deliver additional, innovative data products, the most important of which will be a digital elevation model of the surface of the Earth. TanDEM-X continues the German Earth-observation programme's unique approach of setting up a partnership for commercial data marketing that was successfully implemented for the first time in the TerraSAR-X project. During the TanDEM-X mission, scientists will use the unique opportunity to operate it in parallel with the TerraSAR-X satellite. By flying the satellites in close formation, a strategically important –  and for many users essential – global elevation model will be created – and all this with unprecedented quality.

The DLR Microwaves and Radar Institute (DLR-Institut für Hochfrequenztechnik und Radarsysteme), the DLR Remote Sensing Technology Institute (DLR-Institut für Methodik der Fernerkundung) and the German Remote Sensing Data Center (Deutsches Fernerkundungsdatenzentrum; DFD) of DLR cooperate closely in the 'SAR Center of Excellence'. The partner institutions complement each other by covering all relevant fields, from sensor technology and mission design to high-precision operational processing and value-added end-user products. Together with DLR's German Space Operations Center (Deutsches Raumfahrt-Kontrollzentrum), these institutes are also responsible for building the TerraSAR-X ground segment as well as operating the satellite over a period of five years.


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