TerraSAR-X

Infobox Earth satellite
name = TerraSAR-X


caption =
launch_date = June 15, 2007
launch_vehicle = Dnepr rocket
launch_site = Baikonur Cosmodrome, Kazakhstan
orbit_reference =
orbit_type = Low Earth orbit
orbit_altitude = km to mi|514|abbr=yes
orbit_inclination = 97.44°
orbit_repeat = 94.92 minutes
orbit_swath =
orbit_crossing =
mass = 1230 kg

TerraSAR-X is a German Earth observation satellite that uses an X-band SAR to provide high-quality topographic information for commercial and scientific applications. Launched 15 June 2007 aboard a Dnepr rocket from Baikonur, it produced preliminary imagery on June 19 2007. Development was a joint project between the German Aerospace Center (who contributed 100 million Euros to the project) and EADS Astrium (contributed 30 million Euros). Infoterra holds the exclusive commercial exploitation rights.

The satellite works in the X-band (wavelength 31 mm, frequency 9.6 GHz) and is called therefore TerraSAR-X. The short wavelength makes the technical development a little more difficult but permits a high resolution of the digital radar images, up to 1 meter at the earth's surface.

Pro and cons of radar technology

RADAR stands for "Radio Detection and Ranging" and contains traditionally:
* Range finding (EDM) by means of the time a reflected signal needs to return;
* Direction measurement over the adjustment of the antenna, and recently;
* also different analysis such as SAR, polarization, Interferometry etc.

Satellites with radar technology are still relatively new compared to optical camera systems. The resolution (detail sharpness) is in principle smaller, but radar has other advantages: the lower the frequency, the more easily the radiation penetrates the ground surface including vegetation and soils to detect hidden features (e.g., soil moisture and structure, roots, geology, buried bodies, unexploded ordnance (UXO) such as mines, etc).

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. Nowadays we can measure for instance the speed of other satellites to mm/sec exactly (GRACE), and the slow deformation of volcanos. The military has used radar since the late 1930s and RADAR satellites at least since since 1978. [(Jensen, J. R. 2007. Remote Sensing of the Environment: An Earth Resource Perspective)]

Innovations with TerraSAR X

TerraSAR X will exhibit some technical-industrial novelties. One of these innovations is a kind of zoom shot, with the dissolution 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.

ize, Scanning and planned trajectory

TerraSAR X is 5 meters high and weighs about 1230 kg and circles the Earth with a nearly polar orbit at approximately 500 km altitude.

Because of the tiltable radar and other course refinements (precession by the earth flattening) any place on earth can be observed preferentially within 1-3 days.

More exactly, TerraSAR X will fly over the same point of the earth's surface every 11 days (Note: the revisit time of the satellite varies depending on the specific latitude of the spot in question. Due to the polar orbit of the satellite, areas nearer to the poles will be revisited much more frequently than areas nearer to the equator).

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

Applications of space-based radar imagery of Earth include measurement of elevation changes of the Earth's surface, the production of maps, geosciences such as hydrology (soil dampness etc.) and meteorology, land use monitoring for agriculture, forest management, and environmental protection.

ee also

* Seasat: The first SAR radar in space in 1978
* SAR Lupe: Germany's military radar satellitesRadars on the Space Shuttle:
* SIR-A (Shuttle Imaging Radar) aboard STS-2 in 1981
* SIR-B aboard STS-41-G in 1984
* SRL-1 (Shuttle Radar Laboratory): SIR-C (Spaceborne Imaging Radar) and X-SAR (X-Band Synthetic Aperture Radar) on STS-59 in 1994
* SRL-2: SIR-C/X-SAR on STS-68 in 1994
* SRTM (Shuttle Radar Topography Mission) on STS-99 in 2000(the TerraSAR-X authors were involved in SRL and SRTM missions)

References

External links

* [http://wwwserv2.go.t-systems-sfr.com/tsx/start_en.htm Mission Statement] at DLR website.
* [http://www.terrasar.de/ Infoterra GmbH]
* [http://www.space-risks.com/SpaceData/index.php?id_page=8&Satellite_Name=TERRASAR-X TerraSAR-X] for risk management.
* [http://www.invent-gmbh.de/ Invent GmbH] the manufacturer of CFRP wave guides in service on TerraSAR-X.