SMAPVEX12 stands for the 2012 Soil Moisture Active Passive (SMAP) Validation Experiment.
SMAP is a NASA Earth science satellite mission that uses microwave radar and radiometer instruments to measure soil moisture from space. The radar and radiometer share a six-meter mesh reflector antenna that rotates at approximately 14 revolutions per minute. The instrument system is mounted on a dedicated spacecraft that will be launched into space in October 2014 if all goes well, and will orbit the Earth approximately every 90 minutes at a height of 685 km above the Earth’s surface. The instruments will measure the microwave radiation emitted and scattered from the land surface, and will transmit the measured data down to Earth where the data will be converted into global maps of soil moisture. The maps will also show whether the moisture in the soil is liquid or frozen at any given time.