NASA's new soil moisture satellite: TU Wien validates data
With NASA’s launch of SMAP, a new soil moisture satellite will orbit the Earth. The Soil Moisture Active Passive (SMAP) satellite is designed to provide global maps on soil moisture in the top centimeters of the soil. The amount of water in the soil plays an important role in the hydrological cycle and in occurrence of droughts and floods. Also in the carbon cycle soil moisture plays an important role: for example, vegetation growth and especially crop production, depends on the amount of water available in the soil for the plants. With data from NASA’s new satellite, and existing European satellites like SMOS and MetOp, soil moisture data is daily available on a global scale and will help improve weather predictions, flood forecasts and early warnings given to farmers to irrigate their lands.
SMAP has two different sensors on board. A radiometer which measures soil moisture accurately, but on measurement covers a large area of ca. 40 km. The second sensor is a radar, which takes a measurement every 10 km, but is less accurate. By combining the data from the two sensors accurate soil moisture data every 10 km will be available. Furthermore, SMAP is the first instrument to use a large mesh antenna which will rotate. After launch, when SMAP is in orbit, the antenna will be unfolded like an umbrella and will have a diameter of 6 meters, making it the largest rotating antenna of its kind by NASA.
In the first months SMAP data will be validated over various control points around the world in order to check the quality of the data and improve the soil moisture retrieval models. One of these control points is the Hydrological Open Air Laboratory managed by the Vienna Doctoral Programme on Water Resource Systems at TU Wien. At the HOAL in Petzenkirchen the water content in the soil is measured continuously at different locations since researcher Mariette Vreugdenhil installed it in August 2013. Here Mariette works on comparing the soil moisture data measured in the field to data from different soil moisture satellites. The next months she will work with the SMAP science team to better understand the data from the new satellite. She will work at both NASA’s Jet Propulsion Laboratory in Pasadena, California and Massachusetts Institute of Technology in Boston (MIT). Some of the problems she will investigate is how the soil moisture signal is affected by water in the vegetation and how radiometer and radar data from SMAP can be combined.