Satellite Remote Sensing RADARSAT
The RADARSAT satellite was launched on 4 November 1995 and has a Synthetic Aperture Radar (SAR) sensor on board. This sensor can operate in a variety of imaging modes to suit a range of applications.
The SAR sensor is an active microwave sensor capable of imaging the Earth regardless of time of day, cloud, haze, or smoke over the area. The instrument is classified as "active" as it emits the microwave energy necessary to image the Earth's surface. In contrast, "passive" or "optical" sensors rely on the sun's reflected energy to image the Earth. This ability to penetrate clouds or smoke makes RADARSAT extremely useful in flood and fire situations, or over regions that are constantly covered in cloud.
The SAR sensor on RADARSAT also has the unique capability to acquire data in any of a possible 25 imaging modes. Each mode varies with respect to swath width, resolution, incidence angle, and number of looks. Because different applications require different imaging modes, RADARSAT gives users tremendous flexibility in choosing the type of SAR data most suitable for their application. The following diagram shows most of the image modes available.
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| RADARSAT Image of the Daly River in flood, during the passage of Cyclone Les in 1998. | Flood map derived from the RADARSAT image. Dark Blue is open water, light blue is flooded woodland. |
This flexibility of capture mode also allows the creation of stereo pairs, from which height information such as contours and DEMs can be created.
