27 February 2015 And then there were three
Following its succesful launch on 31 January 2015 the NASA SMAP (Soil Moisture Active Passive) satellite has deployed the 6 metre diameter antenna. SMAP is the third satellite in orbit capable of measuring sea surface salinity globally, the first two being the European Space Agency SMOS (launched Novemeber 2009) and the NASA/CONAE Aquarius (launched June 2011) missions.
See http://smap.jpl.nasa.gov/ for more details.