The human eye works as a passive device, since the object is illuminated by sunlight or other light sources. However, radar produces its own illumination via electromagnetic waves, which means that it is an active device. The military uses radar for surveillance and weapons control. The geometry of imaging radar.
Research scientists use radar as a measurement tool.
Radars have been placed on satellites, space modules, and shuttles to explore meteors, planets, and other objects in the solar system. In the case of an imaging radar, the radar travels along an airplane's or a space shuttle's flight path. The area underneath is illuminated by the radar, and the radar architecture builds the image as it moves on the top of its footprint. The radar image's finer resolution is achieved by using a very long antenna array to focus the transmitted and received energy into a sharp beam. In the following sections, we introduce and explain different types of SAR imaging techniques.