SeaWinds-1B: a combination of ku-band scatterometer and wind radiometer for global ocean wind measurements

Satellite wind scatterometers are microwave radar instruments designed specifically to measure near-surface wind speed and direction over the global ocean. NASA has a long term commitment to ocean wind remote sensing, starting from Seasat-A Satellite Scatterometer (SASS),through NASA Scatterometer (NSCAT), to SeaWinds. SASS was launched in June, 1978 and operated for three months. NSCAT was launched on Japan's Advanced Earth Observation Satellite (ADEOS) in August, 1996, and SeaWinds will be launched on ADEOS-2 in 1999. As a continuation of the NASA wind measurement program, we are developing a next generation wind vector measurement instrument, called SeaWinds-1B, scheduled to be launched in year 2003 on Japan's Advanced Earth Observation Satellite-3 (ADEOS-3). The purpose of this paper is to present the system parameters and system design of this new instrument. SeaWinds-1B is a combination of two instruments into a single design: scatterometer, and polarimetric wind-radiometer (WINDRAD). The scatterometer instrument is used as a baseline to continue the active microwave wind measurements. The WINDRAD instrument is incorporated to demonstrate a new concept of wind vector measurements from space using polarimetric radiometer. WINDRAD can also be used to measure the atmospheric attenuation to improve the scatterometer measurement accuracy. Furthermore, the combination of the scatterometer and WINDRAD will improve the accuracy of the wind vector measurements and the skills for removing the wind direction retrieval ambiguity.