Friday, 05 24th

Last updateThu, 26 Sep 2013 11am

SAR

The use of SAR technology began in the '70s with planetary exploration. The Magellan Mission provided SAR images of the surface of Venus while the Cassini Mission provided similar images of Titan, the largest moon of Saturn.

In 1978, NASA, the U.S. space agency, launched the SEASAT satellite into Earth’s orbit, which carried onboard a SAR sensor to monitor the Earth's oceans. From that date, many different SAR missions have followed over time and currently many space agencies manage programmes for the regular acquisition of SAR images both for scientific purposes and for commercial applications.

Currently, synthetic aperture radar is one of the best technologies for remote sensing because of the high spatial resolution of the images produced, given the wide range of acquisition and their non-dependence on weather conditions and sunlight thus overcoming the limitations of other forms of remote sensing techniques such as optical infrared images.

However, the main advantage of the SAR technology is the particular form of coherent light that can be used in special measurement configurations such as SAR interferometry (InSAR) to produce images derived from SAR images to provide useful information on the morphology of the observed scene and on its displacements. This particular feature has led to commercial applications of both SAR satellite images and of those acquired with ground-based SAR sensors.

The application currently most in demand is the measurement of displacement maps of ground surfaces or major infrastructures.

These are provided with an accuracy equal to a fraction of the wavelength of operation of the SAR and therefore equal to a fraction of a millimetre in ground based SAR applications and of a few millimetres in satellite applications.

SAR systems can be realized in monostatic or bistatic configuration: the monostatic SAR transmits and receives from the same position while the bistatic make use of two: one for transmission and another for the reception, on different platforms.

The bistatic configuration, in addition, can be generalized to the multistatic case, in which more antennas are used for the reception.

The bistatic SAR systems can be realized with ground based SAR, with satellite SAR and SAR jointly using ground-based and satellite sensors.

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