SRTM C-band topographic data: quality assessments and calibration activities

In February 2000 the Shuttle Radar Topography Mission (SRTM) mapped the topography of the world's landmasses between /spl plusmn/60/spl deg/ using radar interferometry. The radar instrument, designed for global coverage, is a two-aperture C-band interferometer, comprising a modified SIR-C C-band system and an added receive antenna mounted at the end of a 60 m deployable boom. Full coverage of the Earth was possible in the 10 day mission by operating the radar in two two-beam ScanSAR modes, one with vertical polarization, and the other with horizontal polarization. The four beams together covered about a 225 km ground swath. An additional X-band interferometer was also flown on the shuttle, with a narrower swath. One of the key components of the interferometer was the Attitude and Orbit Determination Avionics (AODA), comprising a suite of instruments to measure the shuttle position and attitude and the boom tip location relative to the shuttle. Absolute position information was determined from two GPS receivers located on the deployed radar antenna structure. Attitude information was derived from a combination of star tracker and IRU measurements. The boom tip location was determined with an optical target tracker, which measured the angles to several targets located on the tip structure, and an electronic ranging device used to measure the distance to the boom tip.