We have examined the L-band radiometer and radar data from NASA’s Soil Moisture Active Passive (SMAP) mission for ocean research and applications. We find that the SMAP data are in excellent agreement with the geophysical model function (GMF) derived from the Aquarius data up to a wind speed of 20 ms<sup>-1</sup>. For severe wind conditions, the higher resolution data from SMAP allowed us to assess the sensitivity of L-band radiometer signals to hurricane force winds. We applied the L-band GMF to the retrieval of ocean surface wind and SSS from the SMAP data. Comparison with the European Center for Medium-Range Weather Forecasting, WindSat and RapidSCAT wind speeds suggests that SMAP’s radiometer wind speed reaches an excellent accuracy of about 1.1-1.7 ms<sup>-1</sup> below a wind speed of 20 ms<sup>-1</sup>. We have also found that the maximum wind speed derived from the SMAP radiometer data can reach 140 knots for severe storms and are generally in good agreement with the hurricane track analysis and operational aircraft Stepped Frequency Microwave Radiometer wind speeds. The spatial patterns of the SMAP SSS agree well with climatological distributions, but exhibit several unique spatial and temporal features.
Measurement of ocean surface salinity dynamics from space poses numerous engineering and scientific challenges that
push the boundaries of ocean remote sensing capabilities. The principles of measuring sea surface salinity (SSS) from
space are well established. They involve precise determination of the dielectric characteristics of seawater through lownoise
passive microwave (MW) radiometer measurement of the ocean's brightness temperature (TB), optimally
performed at a low frequency near 1.4 GHz (L-band). Sea surface salinity from space clearly presents new challenges
because science requirements impose the need for resolution of the order of 0.1 psu (practical salinity units). This
requirement means that competing terms carried in the ocean TB measurements, foremost being sea surface temperature
(SST) and ocean surface roughness, must be accounted for in a new and more robust manner. To reach this aim, we
developed consistent forward electromagnetic/geophysical models for the expected surface roughness and foam
emissivity signatures  at L-band. We also provided models to correct for sunglint  and galactic radiation 
scattered towards the future SMOS sensor. Finally, we have defined the Auxiliary data processing for SMOS, including
the processing to get the key SST and wind fields needed for the salinity retrieval .
Prior to launch, airborne field measurement efforts are currently on going to perform algorithm validation exercises.
Here, we present results from the ESA airborne Campaign CoSMOS, performed in the North Sea in April 2006. This
campaign was conducted to help to clarify and bound the limits of uncertainty for the geophysical factors affecting sea
surface emissivity at L-band, in order to develop successful salinity inversion algorithms.