SeaWinds on QuikScat radiometric measurements and calibration

Originally designed as a radar scatterometer, SeaWinds measurements have recently been expanded to include brightness temperature of the Earth. Not since 1972, when the S-193 RADSCAT flew on NASA\´s SkyLab, has such a combined active/passive microwave remote sensor in flown in space. Now, with the launch of the SeaWinds on the QuikScat satellite in June of 1999, simultaneous, active/passive measurements are again available for Earth remote sensing. This technological advance is the result of several changes in the SeaWinds instrument configuration compared to previous satellite scatterometers (SeaSat, ERS-1 and -2 and NSCAT). Foremost, SeaWinds uses conical scanning "pencil" beams to simultaneously measure both the surface backscatter and microwave emission. In this paper we describe the radiometric processing and calibration that enables the surface brightness temperature measurement