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TerraSAR-X, an imaging radar Earth observation satellite, is 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.

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TerraSAR-X

Mission type	Radar imaging
Operator	DLR
COSPAR ID	2007-026A
SATCAT no.	31698
Mission duration	Elapsed: 15 years, 2 months, 27 days
Spacecraft properties
Manufacturer	EADS Astrium
Launch mass	1,230 kg (2,710 lb)
Start of mission
Launch date	15 June 2007, 02:14 (2007-06-15UTC02:14Z) UTC
Rocket	Dnepr
Launch site	Baikonur 109/95
Contractor	ISC Kosmotras
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Semi-major axis	6,886.39 kilometres (4,279.00 mi)[1]
Eccentricity	0.0001445[1]
Perigee altitude	514 kilometres (319 mi)[1]
Apogee altitude	516 kilometres (321 mi)[1]
Inclination	97.44 degrees[1]
Period	94.79 minutes[1]
Epoch	25 January 2015, 02:35:23 UTC[1]

Satellite and mission

With its phased array synthetic aperture radar (SAR) antenna (X-band wavelength 31 mm, frequency 9.6 GHz), TerraSAR-X provides high-quality radar images of the entire planet from an Earth polar orbit of 514 km 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 reliably provides radar images with a resolution of up to 1m.

Features of TerraSAR-X:

• resolution of up to 1 m,
• high radiometric accuracy,
• high geometric accuracy,
• quick site access time of 2.5 days max. (2 days at 95% probability) to any point on Earth,
• agility feature (rapidly switches between imaging modes and polarisations)

TerraSAR-X imaging modes

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

• SpotLight: up to 1 m resolution, scene size 10 km (width) × 5 km (length);
• StripMap: up to 3 m resolution, scene size 30 km (width) × 50 km (length);
• ScanSAR: up to 16 m resolution, scene size 100 km (width) × 150 km (length);[2]

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:

• Single Look Slant Range Complex (SSC)
• Multi Look Ground Range Detected (MGD)
• Geocoded Ellipsoid Corrected (GEC)
• Enhanced Ellipsoid Corrected (EEC)

TanDEM-X and WorldDEM Akida

TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is a second, similar spacecraft launched successfully 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 only a few hundred metres and record data synchronously.[3] 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.[4]

Satellite radar

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;
• Different analysis such as SAR, polarization and Interferometry.

Satellite radar entered use more than fifteen years after optical camera systems did. 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.[5]

Innovations with TerraSAR X

TerraSAR X will exhibit 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 1–3 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

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

• Topographic Mapping: 2D and 3D, in scales down to 1:25,000, map updates
• Surface Movement: Based on timeseries acquired by TerraSAR-X over the same area surface displacements caused by subsurface mining, oil-/gas extraction, infrastructure construction, excavations, or underground engineering can be visualised.[6]
• Change Detection: for the monitoring of large-scale construction projects, infrastructure networks, monitoring and documentation of changes and developments
• Land Cover and Land Use Mapping: accurate and up-to-date land cover / land use informations, also from places, where it is difficult to get informations with using other technologies because of permanent cloud cover
• Defence and Security Applications: Applications include effective mission planning, the quick assessment of natural or manmade disasters or border control through detection of paths (changes), fences and moving objects
• Rapid Emergency Response: due to its rapid revisit time TerraSAR-X is a reliable source of information in case of natural or man-made disasters (e.g. earth quakes, floods, military conflicts etc.) providing reliable information for disaster management and response allowing the recognition and assessment of damages to populated areas and traffic infrastructure, the identification of focus areas, and an efficient coordination of rescue actions.[7][8]
• Environmental applications: e.g. forest monitoring, flood monitoring,[9] water quality applications
• Further applications currently under evaluation: Traffic Monitoring, Maritime applications, vegetation monitoring

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.[10] 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

In order 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

• OPS 3762: The very first SAR radar in space, 1964
• Seasat: The SAR radar in space in 1978
• SAR Lupe: Germany's military radar satellites
• SAR technology(Synthetic Aperture Radar)
• Earth observation technology
• Earth observation satellite
• Digital elevation model

Radars 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

• Astrium Geo
• TerraSAR-X at DLR website.
• TerraSAR-X^{[permanent dead link]} for risk management.
• TanDEM-X at DLR website.
• TanDEM-X Science Home at DLR website
• Terrasar-x at Astrium website

На других языках

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[de] TerraSAR-X

TerraSAR-X („Terra“: lateinisch für die Erde, SAR: Synthetic Aperture Radar, „X“ für das X-Frequenzband [Mikrowellen, 8–12,4 GHz]) ist ein deutscher Erdbeobachtungssatellit, der im Rahmen einer Public-Private-Partnership (PPP) zwischen dem DLR und Airbus Defence and Space realisiert wurde. Die exklusiven kommerziellen Nutzungsrechte liegen bei der Airbus Defence and Space GmbH. TerraSAR-X wurde am 15. Juni 2007 gestartet und hat im Januar 2008 seinen operativen Betrieb aufgenommen.[1][2]

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- [en] TerraSAR-X

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[es] TerraSAR-X

TerraSAR-X es un satélite radar de observación de la Tierra construido en el marco de la colaboración público-privada entre el Centro Aeroespacial Alemán (DLR) y EADS Astrium. TerraSAR-X fue lanzado el 15 de junio de 2007 y está operativo desde enero de 2008. Junto con su satélite gemelo TanDEM-X, lanzado el 21 de junio de 2010, TerraSAR-X ha adquirido la base de datos WorldDEM, el Modelo Digital de Elevación global. Los derechos de explotación comercial exclusivos son propiedad de Infoterra GmbH, una filial propiedad al 100 % de EADS Astrium.

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[ru] TerraSAR-X

TerraSAR-X — немецкий спутник дистанционного зондирования Земли, предназначен для радарной съёмки поверхности Земли в гражданских интересах. Спутник запущен 15 июня 2007 с космодрома Байконур с помощью ракеты-носителя «Днепр».

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