Synthetic Aperture Radar
Synthetic Aperture Radar Synthetic
aperture radar (SAR) is basically a method of ground mapping that uses computer
processing to make radar work better. It first appeared in the early 1950s but
didn't reach a high state of development for almost 30 more years with the
introduction of digital processing and other advances. SAR
yields high-resolution, photograph-quality images because it combines radar
images made many miles apart. SAR uses antennas positioned on moving bodies,
such as satellites, and then mathematically combines the separate signals
transmitted as the antenna moves, simulating or mimicking the transmission of
radar from a source with a larger “aperture,” or a larger opening. For
instance, a European Space Agency satellite with a 10-meter SAR antenna mimics
the performance of a 4-kilometer-long stationary antenna. The motion of the satellite, combined with the wide beam of
the radar, covers a swath along the ground, allowing a large area to be
searched quickly--typically 256 square kilometers. If a few dozen of these
swaths are collected, an area of several thousand square kilometers will be
covered. One use for SAR is in searches
associated with satellite-based search and rescue systems. |