Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) is a joint project of the National Aeronautics and Space Administration (NASA), the German Space Agency, Deutsche Agentur fur Raumfahrtangfelegenheiten (DARA), and the Italian Space Agency, Agenzia Spaziale Italiana (ASI). An imaging radar system launched aboard the NASA Space Shuttle twice in 1994, SIR-C/X-SAR's unique contributions to Earth observation and monitoring are its capability to measure, from space, the radar signature of the surface at three different wavelengths and to make measurements for different polarizations at two of those wavelengths. The SIR-C image data help scientists understand the physics behind some of the phenomena seen in radar images at just one wavelength/polarization, such as those produced by SeaSAT. Investigators on the SIR-C/X-SAR Science team use the radar image data to make measurements of vegetation type, extent and deforestation, soil moisture content, ocean dynamics, wave and surface wind speeds and directions, volcanism and tectonic activity, and soil erosion and desertification. The SIR-C provides multi-frequency, multi-polarization radar data.The SIR-C instrument is composed of several subsystems: an antenna array, a transmitter, receivers, a data-handling subsystem, and a ground SAR processor. The data are processed into images with selectable resolution from 10 to 200 meters. The width of the area mapped by the radar varies from 15 to 90 kilometers, depending on how the radar is operated and on the direction in which the antenna beams are pointing. Data from SIR-C/X-SAR are used to develop automatic techniques for extracting information from radar image data.
