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Overview |
TerraSAR-X is a 1 meter resolution class radar satellite from Germany. It carries a high frequency X-band SAR sensor that can be operated in different modes (resolutions and swath) and varying polarization. TerraSAR-X's high resolution (upto1m) imagery is complementary to high resolution optical systems. Being a highly agile weather independent sensor, TerraSAR-X provides vital data for various applications such as resource monitoring, defense, agriculture and hazard management to name a few.
TerraSAR-X sensor can be operated in different modes and polarisation. The SpotLight- (1 m), StripMap- (3m) and ScanSAR-modes (16 m) provide high resolution SAR images for detailed analysis as well as wide swath data whenever a larger coverage is required. Imaging is possible in single, dual and quad-polarisation. Beam steering enables observation in different incidence angles. Nominally TerraSAR-X is a right looking system but the spacecraft may also be operated in left-looking mode or with a wider range of incidence angles defining the data access range. |
Imaging Modes
Data can be acquired in one of three main Image Modes:
- SpotLight (up to 1 m resolution, 10 km x 5 or 10km)
- StripMap (up to 3m resolution, 30km x up to 1,500 km)
- ScanSAR (up to 16m resolution, 100km x up to 1,500km)
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SpotLight (SL) and High Resolution SpotLight Mode (HS) |
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TerraSAR-X achieves the highest geometrical resolution in the SpotLight mode. During the observation of a particular ground scene the radar beam is steered like a spotlight so that the area of interest is illuminated longer and hence the synthetic aperture becomes larger. The size of the observed area on ground is smaller than the one in all other modes. HS and SL modes are very similar. In SL mode the geometric azimuth resolution is reduced in order to increase the azimuth scene coverage. |
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StripMap Mode (SM) |
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In StripMap Mode the ground swath is illuminated with a continuous sequence of pulses while the antenna beam is fixed in elevation and azimuth. This results in an image strip with continuous image quality in azimuth at a resolution of 3 metres. |
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ScanSAR Mode (SC) |
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The ScanSAR mode provides a large area coverage. The wider swath is achieved by scanning several adjacent ground sub-swaths with simultaneous beams, each with a different incidence angle. Due to the reduced azimuth bandwidth the azimuth resolution of a ScanSAR product is lower than in StripMap mode. Areas of up to 100,000 km2 anywhere on the globe can be covered in TerraSAR-X’s 16 m resolution within only a week. In the ScanSAR mode, a swath width of approx. 100 km can be achieved by scanning four adjacent ground sub-swaths with quasi-simultaneous beams. |
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Polarisation |
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Each pulse can be transmitted either vertically (V) or horizontally (H) polarised. The back-scattered signal can be received with either vertical or horizontal polarisation, independent from the transmit polarisation. The resulting product consists of one polarimetric channel in one of the combinations HH, HV, VH or VV.
In dual polarisation mode the radar toggles the transmit and/or receive polarisation on a pulse to pulse basis. The effective PRF (Pulse Repetition Frequency) in each polarimetric channel is half of the total PRF, which means that the azimuth resolution is slightly reduced. The product consists of two layers that can be selected out of the possible combinations.
Single Polarization and Dual Polarization are the two standard modes which are possible for each image mode, except ScanSAR, which is restricted to single polarization.
Quad polarisation is possible in the experimental dual receive antenna mode as the signal can be received simultaneously in H and V polarisation.
Currently, Quad polarisation products are not available commercially. |
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Products |
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By Geometry
- Single Look Slant Range Complex (SSC)
- Multi Look Ground Range Detected (MGD)
- Geocoded Ellipsoid Corrected (GEC)
- Enhanced Ellipsoid Corrected (EEC)
By Polarisation
- single or dual in HH, VV, HV, VH combinations
By Image Mode
- SpotLight
- StripMap
- ScanSAR
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All detected products (only exception: ScanSAR) are available in two resolution flavors, a spatially enhanced version and a radiometrically enhanced version. As standard polarization modes, single and dual are supported. Due to its considerable operational mission restrictions, data acquisition in the left-looking mode is not a standard feature available for users. However, left-looking products can be generated and distributed. |
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Value Added Products |
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- Enhanced Image Products
- Orthorectified image
- Mosaic
- Oriented Image
- Ascending / Descending Merge
- Geo-Information Products
- Orthomap
- Change Detection Map
- Subsidence Map
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TerraSAR-X: Core advantage |
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- First commercial 1m SAR Satellite Imagery
- Rapid data acquisition due to short system response time(up to few hours)
- Repeated coverage at different viewing angles
- Interferometry capability
- Weather and illumination independent due to microwave frequency
- Simultaneous dual polarization
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Applications |
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TerraSAR-X derived products have variety of application in diverse fields.
Agriculture
- Mapping of acreage / detection of small fields
- Mapping of field heterogenities
- Crop type recognition
- Growth stage assessment
- Crop parameter assessment
Forestry
- Tree type identification
- Mapping of disturbances caused by fire, insect attacks, deforestation
- Forest Parameter Assessment
Land cover mapping
- Mapping of broad land cover and land use classes
- Change detection analysis
Urban areas
- Extent of settlements
- High precision settlement mapping
- Characterization of urban areas
- Delineation of infrastructure
- Traffic monitoring
Topographic mapping
- Repeat-pass interferometry
- Radargrammetry
Disaster management
- Risk and vulnerability assessment
- Monitoring of hazard prone zones
- Planning and management of rescue operations
- Damage assessment
Geological mapping
- Features and structures
- Lithology
Disaster management
- Landslides
- Volcanoes
- Earthquakes
Snow and ice
- Snow extent
- Snow parameters
- Glacier mass balance
- Glacier ice motion
Soil moisture
Groundwater resources
Wetlands
Wind and waves
- Wind speed and direction
- Wave direction and height
Ocean dynamics
Sea ice
- Iceberg detection
- Sea ice extent
- Sea ice type mapping
- Sea ice draft
Ship detection
- Ship and wake detection
- Ship speed estimation
Oil slicks
Coastal protection and change monitoring
- Delineation of coastline
- Mapping and monitoring of major land cover types, e.g. mangroves
Bathymetry
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