SeaWinds beam and slice balance using data over Amazonian rainforest

The primary application of a scatterometer is estimation of wind vectors over the sea surface, but a variety of other geophysical parameters can be retrieved as well. To eliminate ambiguity in retrieved wind direction, multiple looks are required at the observed area. These looks are provided by multiple scatterometer antenna beams. To achieve the desired accuracy of wind vectors and other retrieved geophysical products, the antenna beams must be calibrated to within /spl plusmn/0.2 dB. Pre-launch calibration alone is insufficient for such a level of beam balance. Postlaunch calibration/validation activities are therefore required for scatterometer missions. This paper describes beam balance procedure applied following the recent launch of the SeaWinds scatterometer on the QuikScat spacecraft. This work was similar to the NSCAT post-launch verification. A brief description is given of the SeaWinds instrument. A calibration data set is introduced. An azimuth beam balance and a comparison with preceding NSCAT instrument is presented. High-resolution slice-balance results are also shown.