Spaceborne Imaging Radar
The Spaceborne Imaging Radar (SIR) - full name 'Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR)', is a Synthetic Aperture Radar which was launched from the Space Shuttle Endeavour in April (STS-59) and October (STS-68) of 1994. The radar was run by NASA's Space Radar Laboratory. SIR utilizes 3 radar frequencies: L band (24 cm wavelength), C band (6 cm) and X band (3 cm), allowing for study of geology, hydrology, ecology and oceanography. Comparing radar images to data collected by teams of people on the ground as well as aircraft and ships using simultaneous measurements of vegetation, soil moisture, sea state, snow and weather conditions during each flight.
The SIR mission revealed hidden river channels in the Sahara Desert indicating significant climate change in the past. SIR was also used for volcano research by keeping researchers a safe distance from hazardous and often inaccessible areas. The radar was also used to generate detailed three dimensional mappings of the Earth's surface.