Performance and Capabilities of the New Compact Ocean Wind Vector Radiometer System

The paper describes the performance and capabilities of a new satellite conically imaging microwave radiometer system, the Compact Ocean Wind Vector Radiometer (COWVR), being built by the Jet Propulsion Laboratory (JPL) for an Air Force demonstration mission. COWVR is an 18-34 GHz fully polarimetric radiometer designed to provide measurements of ocean vector winds with an accuracy that meets or exceeds that provided by WindSat, but using a simpler design which has both performance and cost advantages. One of the most significant performance advantages of the COWVR design as it relates to wind vector retrieval is that it provides observations of the scene at two azimuth angles. Multi-look polarimetric radiometry improves the overall wind direction retrieval accuracy, particularly at low winds, and removes any dependence on a priori information by providing a solution free from ambiguities, which are inherent to single-look retrievals. COWVR will be the first satellite radiometer to fully exploit and demonstrate this capability over its full swath. This paper will first give an overview of the COWVR instrument and mission and its calibration performance estimated from laboratory test data. The focus of the paper will be on the two-look retrieval algorithm developed for COWVR and the significant performance improvement it offers over single look retrievals currently being used. The performance improvement is estimated by applying the two-look retrieval algorithm developed for COWVR to the narrow portion of the WindSat swath which contains both fore and aft observations and evaluating the retrievals against independent observations from buoys. We find that the most significant improvement is for low winds (2-6 m/s) where prior single look retrieval algorithms have generally been weak. COWVR is currently in flight fabrication at JPL, having successfully passed its Critical Design Review in June 2014. It will be flight ready in September 2015 and is planned for launch no earlier than 2016. The COWVR mission is intended to demonstrate a new class of low-cost, but equally capable conically imaging microwave sensors well suited for deployment on smaller, lower cost satellites.