Analysis of the Ascat 3-dimensional Measurement Space

The ASCAT instrument onboard MetOp is a real aperture vertically polarized C-band radar with high radiometric stability. It has two sets of three fixed fan beam antennas, each set pointing at either side of the sub-satellite track. Because of the similarities of both the ERS (scatterometer) and ASCAT measurement systems, we have the opportunity to use the ERS geophysical model function (GMF) as a calibration tool for ASCAT. A method, based on the visualization of the 3-dimensional measurement space, will be used to determine and remove beam-to-beam biases and verify the GMF. This work is expected to contribute to the ASCAT calibration activities during the commissioning phase. As such, a calibration report will be delivered by the end of such phase. After calibration and in order to improve the interpretation of the ASCAT data, the effect of a variety of geophysical parameters, such as wind variability or wave age, will be investigated. For such purpose, the maximum likelihood estimator (MLE) magnitude and sign and the ASCAT-derived winds will be compared against numerical model output. A final report, which will also include the calibration results, will be delivered at the end of the project.