Designing a spaceborne SAR for multi-mode imaging

RADARSAT is a project sponsored by the Canadian Space Agency (CSA) and in collaboration with the National Aeronautics and Space Administration (NASA). The spacecraft was launched into Sun-synchronous, 810 km orbit for 5.25 year mission by a Delta II rocket from Vandenburg, Western Range in California in November 1995. The RADARSAT is a remote sensing spacecraft that images Earth´s surface with a synthetic aperture radar (SAR). The SAR permits imaging through heavy cloud cover, and thick atmosphere both night and day. Intended ground observations and applications include, soil texture, vegetation conditions, sea ice concentration and dynamics, and geological surface structure. The RADARSAT SAR is currently the most advanced spaceborne SAR in operation. The system is capable of providing standard form of an image, similar to those of previous satellites, covering a swath width of 100 km at 25 to 30 m resolutions. However, unlike its predecessors the RADARSAT system is not restricted to imaging at one fixed angle to the side of the satellite and is able to image any point over a wide range of angles. The system design also makes available a number of alternative imaging modes, in which images covering swaths of 50 km to 500 km can be imaged at resolutions from about 8 m to 100 m. The RADARSAT SAR imaging modes are illustrated. To provide for this operational flexibility the RADARSAT system requires state of the art command control and data handling capabilities. This article gives an overview of the command, control and data handling subsystems developed by SPAR Aerospace for the RADARSAT spacecraft