Soil Moisture and Ocean Salinity (SMOS) level 2 and level 3 products are simulated and characterized over a one-year time period. A simulator is first used to evaluate the sea surface salinity (SSS) error of level 2 SMOS products. An optimal interpolation method is then adapted to map the surface salinity in order to simulate a level 3 SMOS product. The quality of the simulated products is satisfactory. The mean error of the SSS at pixel scale is around 1 psu, and the error on the final gridded product fits the Global Ocean Data Assimilation Experiment requirements (0.2 psu).