An image of the satellites TerraSar-X and TanDEM-X flying over Europe.
Mission typeRadar imaging
COSPAR ID2007-026A Edit this at Wikidata
SATCAT no.31698
Mission durationElapsed: 16 years, 9 months, 8 days
Spacecraft properties
ManufacturerEADS Astrium
Launch mass1,230 kg (2,710 lb)
Start of mission
Launch date15 June 2007, 02:14 (2007-06-15UTC02:14Z) UTC
Launch siteBaikonur 109/95
ContractorISC Kosmotras
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Semi-major axis6,886.39 kilometres (4,279.00 mi)[1]
Perigee altitude514 kilometres (319 mi)[1]
Apogee altitude516 kilometres (321 mi)[1]
Inclination97.44 degrees[1]
Period94.79 minutes[1]
Epoch25 January 2015, 02:35:23 UTC[1]

TerraSAR-X, is an imaging radar Earth observation satellite, a joint venture being carried out under a public-private-partnership between the German Aerospace Center (DLR) and EADS Astrium. The exclusive commercial exploitation rights are held by the geo-information service provider Astrium. TerraSAR-X was launched on 15 June 2007 and has been in operational service since January 2008. With its twin satellite TanDEM-X, launched 21 June 2010, TerraSAR-X acquires the data basis for the WorldDEM, the worldwide and homogeneous DEM available from 2014.

Satellite and mission

Radar image

Using a phased array synthetic aperture radar (SAR) antenna (X-band wavelength 31mm, frequency 9.65 GHz[2]), TerraSAR-X provides radar images of the entire planet from an Earth polar orbit of 514km altitude. This is selected so that the satellite follows a Sun-synchronous orbit. This specific orbit means that the satellite moves along the Day-Night boundary of the Earth and allows it to present the same face to the Sun: thus, providing the best solar incidence angles to its solar cells for power. TerraSAR-X is designed to carry out its task for five years, independent of weather conditions and illumination, and provides radar images with a resolution of up to 1m.

TerraSAR-X imaging modes

TerraSAR-X acquires radar data in the following three main imaging modes:

In addition, the design of TerraSAR-X's SAR antenna allows a variety of polarimetric combinations: single or dual polarization, or full polarimetric data takes.

Depending on the desired application, one of four different processing levels is selected:

TanDEM-X and WorldDEM Akida

TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is a second, similar spacecraft launched on 21 June 2010 from Baikonur Cosmodrome in Kazakhstan. Since October 2010, TerraSAR-X and TanDEM-X have orbited in close formation at distances of a few hundred metres and record data synchronously.[4] This twin satellite constellation will allow the generation of WorldDEM, the global digital elevation models (DEMs). With higher accuracy, coverage and quality – WorldDEM is a consistent DEM of the Earth's land surface is envisaged to be acquired and generated within three years after launch. Available from 2014, WorldDEM is to feature a vertical accuracy of 2m (relative) and 10m (absolute), within a horizontal raster of approximately 12x12 square meters, slightly varying depending on the geographic latitude.[5]

Satellite radar

Radar stands for Radio Detection and Ranging and contains traditionally:

Satellite radar systems came into operation over fifteen years after the adoption of optical camera systems. The resolution is lower than optical imaging, but radar can gather information at any time of the day or night and independent of cloud cover.

Early radar satellite techniques were e.g. the Altimetrie (leveling over the sea), NASA's SEASAT (launched in 1978), regulation of waves/wind or soil data. The military has used radar since the late 1930s and radar satellites at least since 1978.[6]

Novel design features of TerraSAR X

TerraSAR X introduced some technical-industrial novelties. One of these innovations is a kind of zoom shot, with the resolution and scanning field vice versa changeable in a 1:10 relationship, either a larger area to grasp or a small area with the highest possible resolution.

Furthermore, the antenna can be aligned by electronics within an angle range so that the point of view is adjustable. Earlier radar satellites could radiate the antenna only in one direction.

Scanning and trajectory

With the adjustable angle radar sensor – along with other course refinements (precession by the earth flattening) – any place on earth can be observed preferentially within 1 to 3 days.

For a specific point on the Earth's equator, TerraSAR X has a revisit cycle of 11 days. The revisit time decreases towards the poles, e.g. Northern Europe has a revisit time of typically 3–4 days.

Ground segment

The ground operating mechanism and controls for the TerraSAR X is developed by the DLR in Oberpfaffenhofen. It consists of Mission Operating Equipment, the Payload ground segment and the Instrument Operation and Calibration Segment. At the base of the ground segment lies the German Space Operation Center (GSOC), the German Remote Sensing Datum Center (DFD) as well as Institutes for Methodology of Remote Sensing (MF) and the Institute for High-Frequency Engineering and Radar Systems (HR) which are all part of the DLR.


Applications of the high-resolution TerraSAR-X radar imagery include:

Scientific use of TerraSAR-X data

The scientific use of the TerraSAR-X data will be coordinated through the TerraSAR-X Science Service System by the DLR.[11] The new-quality data records, as provided by TerraSAR-X, will offer a vast amount of new research incentives, for instance in ecology, geology, hydrology and oceanography. The smallest movements of the Earth's surface (plate tectonics, volcanism, earthquake) are further scientific fields of application.

Commercial use of TerraSAR-X data

To ensure the commercial success of the mission, EADS Astrium founded its 100% subsidiary Infoterra in 2001; the company being responsible for establishing a commercial market for TerraSAR-X data as well as TerraSAR-X-based geo-information products and services.

See also

The radar remote sensing satellites TanDEM X and Terra SAR X photographed while flying in close formation (photo by Marco Langbroek, Leiden, the Netherlands). Movement is from lower right to upper left in this 10-second exposure.

Radars on the Space Shuttle:

(the TerraSAR-X authors were involved in SRL and SRTM missions)


  1. ^ a b c d e f g "TERRA SAR X Satellite details 2007-026A NORAD 31698". N2YO. 25 January 2015. Retrieved 25 January 2015.
  2. ^ "Observing Systems Capability Analysis and Review Tool: SAR-X Instrument details". World Meteorological Organization. 15 June 2021. Retrieved 7 June 2023.
  3. ^ StripMap & ScanSAR: acquisition length extendable to up to 1,650 km.
  4. ^ DLR – Blogs – The satellites have 'eye contact'
  5. ^ GIM International: Weber, Marco; Koudogbo, Fifamè, January 2009, TerraSAR-X 1m Spaceborne Radar – Use, Features, Products and TanDEM-X.
  6. ^ (Jensen, J. R. 2007. Remote Sensing of the Environment: An Earth Resource Perspective)
  7. ^ GeoBerichte 14, Landesamt für Bergbau, Energie und Geologie in Niedersachsen:Schrage, Thomas;Jacob, Philipp, June 2009, Flächenverbrauch und Bodenversigelung in Niedersachsen.
  8. ^ GIM International: Balz, Timo; Scheuchl, Bernd;Li, Deren, October 2008, The Sichuan Earthquake(1)-Satellite Imagery for Rapid Response.
  9. ^ GIM International: Shao, Yun; Scheuchl, Bernd, November 2008, The Sichuan Earthquake (2)- Spaceborne SAR in Earthquake Response.
  10. ^ GIM International: Koudogbo, Fifamè; Müller, Marc; Scheuchl, Bernd, December 2008, The Sichuan Earthquake (3)- Satellite-based Global Flood Response.
  11. ^ TerraSAR-X Science Service System