Inverse Synthetic Aperture Radar Imaging With MATLAB Algorithms, 2nd Edition

3Synthetic Aperture Radar

Synthetic aperture radar (SAR) is a high‐resolution airborne and spaceborne remote sensing technique for imaging remote targets on a terrain or more generally on a scene. In 1951, Carl Wiley realized that if the echo signal is collected when the radar is moving along a straight path, the Doppler spectrum of the received signal can be used to synthesize a much longer aperture so that very close targets in the along‐track dimension can be resolved (Wiley 1954). In 1953, the first measured SAR image was formed when a C‐46 aircraft was used to map a section of Key West, Florida, US (Cutrona et al. 1960). The first on‐board satellite SAR system was developed by NASA researchers and put on Seasat in 1978. This remarkable satellite provided a lot of data for oceanographic applications. After Seasat, several satellites carrying SAR systems have been launched by different countries. Russian Almaz (1987), European ERS‐1 (1991), ERS‐2 (1995), and Canadian Radarsat (1995) were among some of them. The first space‐shuttle mission that has a SAR module was Shuttle Imaging Radar‐A (SIR‐A). After SIR‐A was launched aboard the space shuttle Columbia in 1981; other spaceborne SAR missions were followed. Shuttle Imaging Radar‐B (SIR‐B) (1984) and SIR‐C/X‐SAR (1994) acquired SAR images in multiple frequencies and polarizations for more advanced applications such as interferometric and polarimetric mapping of terrains.

Although SAR has been primarily utilized for surveillance ...