Sea surface salinity (SSS) measurement is one of the objectives of ESA’s SMOS (Soil Moisture and Ocean Salinity) Earth Explorer Opportunity mission. SMOS’s objective is to provide global soil moisture and sea salinity maps using the MIRAS L-band aperture synthesis interferometric radiometer. Since the sea salinity signature exhibits a very small brightness temperature dynamic margin, it can only be accurately retrieved if the sea surface emissivity at L-band is properly modeled. In addition to the sea salinity signature, other factors influencing the emissivity are the sea surface temperature, and the sea surface roughness induced by wind, the large scale roughness created by swell, and the foam
emissivity. This article is focused on the estimation of the sea surface spectrum, which describes sea roughness, training a neural network with wind and roughness data obtained during WISE 2000/2001 (WInd and Salinity Experiment).