WindSat Overview

WindSat is a polarimetric microwave radiometer developed by the U.S. Navy and the National Polar-orbiting Operational Enviromental Satellite System (NPOESS) Integrated Program Office (IPO) for measuring ocean surface wind speed and direction. WindSat will demonstrate the viability of using polarimetry to measure the wind vector from space and provide operationally usable tactical information to Navy units. The payload provides risk reduction data that the NPOESS IPO will use in the development of the Conical Microwave Imager Sounder (CMIS). WindSat is the primary payload on the DoD Space Test Program's Coriolis Mision.

The WindSat payload is a multi-frequency polarimetric radiometer nominally operating at 6.8, 10.7, 18.7, 23.8, and 37 GHz. Using a conically-scanned 1.83 m offset parabolic reflector with multiple feeds, WindSat will cover a 1025 km active swath (based on an altitude of 830 km) and provide both fore and aft views of the swath. The horizontal ground resolution is determined by the size of the antenna and the altitude. The relatively large WindSat antenna will result in spatial resolutions approximately three times greater than current systems, improving the utility of the imagery data and enabling better measurements in the littoral. The 10.7, 18.7, and 37.0 GHz channels are fully polarimetric; that is, they derive all four Stokes parameters by measuring the six principal polarizations. The 6.8 GHz channel is dual polarimetric (vertical and horizontal) and provides sea surface temperature as a secondary product. The 23.8 GHz channel is also dual polarimetric because its purpose is to correct for atmospheric water vapor which is unpolarized

CPI Involvement

CPI scientists, working with the Naval Research Laboratory, are involved in several key areas of the WindSat mission, primarily in algorithm development. One active area of research is the development and testing of forward model algorithms for the instrument. These algorithms are essential for simulation and characterization of the measurements that will eventually come down from the satellite. Such simulations are important both as input into the continued instrument design and testing, as well as providing realistic simulated data for use in testing the inversion algorithms.

The WindSat inversion algorithms are another active area of research that CPI scientists are involved in. NRL has decided to use the CPI "OPT" retrieval algorithms as the core of the operational WindSat inversion algorithms. CPI is playing a lead role in the development of these algorithms.