SeaWinds on QuikSCAT: postlaunch calibration and validation

The SeaWinds scatterometer was successfully launched aboard the QuikSCAT platform on June 19, 1999. It was designed to accurately determine the speed and direction of ocean surface winds via measurements of the normalized radar cross section, σ₀. Since the retrieved wind vector accuracy depends heavily upon the σ₀ measurement accuracy, the SeaWinds instrument has undergone extensive prelaunch and postlaunch calibration. The postlaunch verification and calibration effort included assessments of instrument functionality and stability, hardware component characterization, data processing algorithm validation, calibration table development, and σ₀ calibration. The achieved accuracy of σ₀ makes SeaWinds on QuikSCAT well suited for a variety of scientific applications over ocean, land, and ice. The authors outline the postlaunch calibration approach and indicate the expected accuracy of SeaWinds on QuikSCAT σ₀ measurements. They focus predominantly on the use of distributed Earth targets, both for addressing the critical issue of spacecraft pointing and for achieving calibration consistency between the backscatter measurements made by SeaWinds´ two antenna beams