(Abbreviated SAR). Radar deployed aboard aircraft and satellites that produces a two-dimensional image of the target surface. The position of an object along the direction parallel to the movement of the observing platform is determined by the Doppler shift of the received signal. Phenomena observed by SAR include swell waves, current patterns imaged because of the varying sea surface roughness due to wave– current interaction, and oil spills and natural films that appear as areas of low image intensity as a result of their damping effect on centimeter-scale surface waves. See also Doppler radar, marine radar, microwave radar, high-frequency radar.
an active sensor transmitting and receiving microwave signals, i
Synthetic aperture radar, or SAR, uses a relatively small antenna to produce a broad beam, and makes use of the Doppler shift of the radar signal moving across the target to synthesize (with extensive computer processing) the azimuth resolution of a very narrow beam.
Observation aircraft may be equipped with sideways looking synthetic aperture radar. SAR is a high resolution ground mapping technique which takes advantage of the forward motion of a vehicle that is carrying a pulsed radar to synthesize the effect of a large antenna aperture. In other words, the larger the radar antenna (aperture), the higher the radar picture's resolution. SAR uses a radar with a very small antenna (such as can be carried in an aircraft) that synthesizes a series of recurring radar pulse returns to simulate the effect of a much larger antenna aperture; thus, the name "synthetic" aperture. SAR is effective in detecting large objects day or night, even through cloud cover.
An instrument that uses radar to see through dark, clouds and fog. This type of equipment is on board only three satellites in the world, including Radarsat and Lacrosse.
Synthetic aperture radar (SAR) is a form of radar in which sophisticated post-processing of radar data is used to produce a very narrow effective beam. It can only be used by moving instruments over relatively immobile targets, but it has seen wide applications in remote sensing and mapping.