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What is SAR

Synthetic Aperture Radar. An active microwave instrument, producing high-resolution imagery of the Earth's surface regardless the present weather. Satellite remote sensing that depends on sunlight illuminating the Earth is restricted by the presence of clouds, fog, smoke, or darkness. Because they include active sensors, Synthetic Aperture Radar (SAR) satellites can operate day or night, regardless of weather conditions . SAR improves on real aperture radar data, by using range direction pulse compression technique, to synthetically increase the antenna's size or aperture.

The signals and phases of targets that are recorded using a small moving antenna are processed to simulate the effect of a large antenna. Several different SAR satellite platforms have been operating over the past two decades; SAR image footprint and resolutions are different for each satellite. Schematic representations of the SAR satellites ERS-1, RADARSAT-1, ERS-2, JERS-1 and ENVISAT are shown below.

 

Satellite data types routinely collected for marine research include sea surface temperature, altimetry and ocean color. Some of the satellites used for this data collection are AQUA, TERRA, SeaWifs, JASON, and Topex Poseidon. SAR images offer a different toolset for marine science because SAR data can detect the fine-scale texture of the sea surface. These data have been used for hurricane studies, ocean feature detection, eddies and vertical motions, pollution and oil spill, hydrocarbon resource exploration, and marine surveillance. Limitations of SAR data include the following: relatively restricted spatial coverage (100-500km), demand-specific collections, and sparse repeat intervals. For this reason, applications of SAR data may tend to focus on specific events or localities rather than examining processes of an entire ocean basin. With the archival of large SAR datasets, however, it is possible to compile basin-wide, long term-coverage, which opens new prospects for satellite SAR in marine science.

For more information about SAR, we recommend these sites:


http://www.asf.alaska.edu/sardatacenter/?q=aboutsar

http://southport.jpl.nasa.gov/desc/imagingradarv3.html

 

 

 
 
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