The SeaWinds scatterometer was developed by NASA JPL, Pasadena, CA, to measure the speed and direction of ocean surface winds. It was then launched onboard the QuikSCAT spacecraft. The accuracy of the majority of the swath and the size of the swath are such that the SeaWinds on QuikSCAT Mission (QSCAT) meets its science requirements despite shortcomings at certain cross-track positions. Nonetheless, it is desirable to modify the baseline processing in order to improve the quality of the less accurate portions of the swath, in particular near the far swath and nadir. Two disparate problems have been identified for these regions. At far swath, ambiguity removal skill is degraded due to the absence of inner beam measurements, limited azimuth diversity and boundary effects. Near nadir, due to nonoptimal measurement geometry, (measurement azimuths approximately 180 apart) there is a marked decrease in directional accuracy even when ambiguity removal works correctly. Two algorithms have been developed: direction interval retrieval (DIR) to address the nadir performance issue and thresholded nudging (TN) to improve ambiguity removal at far swath. We illustrate the impact of the two techniques by exhibiting prelaunch simulation results and postlaunch statistical performance metrics with respect to ECMWF wind fields and buoy data. he became a Member of the Technical Staff, Jet Propulsion Laboratory, Pasadena, CA, where he has simulated the behavior of spaceborne scatterometers (NSCAT and SeaWinds) as well as analyzed the data returned from these instruments. He is interested in statistical techniques for determining and visualizing relationships between remote sensor data and geophysical phenomena. Brian D. Pollard received the B.S. in electrical engineering from the University of Houston, Houston, TX, in 1992. He joined the Microwave Remote Sensing Laboratory (MIRSL), University of Massachusetts, Amherst, in 1992, where he received the Ph.D. degree in electrical engineering in 1998.His work at MIRSL included the development of a digitally beamformed volume-imaging radar for atmospheric boundary layer (ABL) studies and compared data from that instrument to large-eddy simulations of the ABL. He joined the Jet Propulsion Laboratory, Pasadena, CA, in 1998, where he studied the design and application of scatterometry, altimetry, and interferometry for airborne and spaceborne remote sensing of the ocean surface. His interests include high-resolution scatterometry and interferometry for oceanic, terrestrial, and planetary applications.
R. ScottDunbar is a Senior Engineer at the Jet Propulsion Laboratory, Pasadena, CA. He has been involved in the NASA Scatterometer (NSCAT) and SeaWinds projects since 1985, contributing to science algorithm development and ground system operations.