Based on the experiences gained during airborne, polarimetric radiometer missions over the North Sea and the Atlantic Ocean in 1996, a new polarimetric radiometer system has been developed. The system features polarimetric channels at 16 and 34 GHz. The radiometers are built to the highest standards concerning stability, which is of paramount importance considering the typically weak brightness temperature wind signatures from the ocean surface. The 1 m aperture, scanning antenna system used previously is reused. The digital correlators and the PC based data recording system are copies or very similar to previous systems. A major new addition is an accurate attitude measurement system. The polarimertic signals are small and at the same time the brightness temperature of water is quite dependent on incidence angle. This combination necessitates measurement of antenna attitude (especially roll and pitch) to within a fraction of a degree. To do this, the inertial navigation unit is mounted directly on the antenna mounting frame, and data recorded on the PC along with the polarimetric radiometer data. Corrections for minor attitude deviations from nominal is then possible in the data processing. Test flights on a C-130 from the Royal Danish Air Force was carried out in the spring of 1998, and major campaigns measuring winds over the ocean were carried out in the fall of 1998. The instrument performed as expected, and is ready for further scientific experiments.
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