SMOS

Simulated seasonal (winter) soil mositure map of Europe and Africa

A novel instrument has been especially developed to make these observations and the objective is also therefore to demonstrate the use of a new radiometer that is capable of observing both soil moisture and ocean salinity by capturing images of emitted microwave radiation around the frequency of 1.4 GHz (L-band). SMOS will carry the first-ever, polar-orbiting, space-borne, 2-D interferometric radiometer.
 
In summary, the SMOS science objectives are to:

• globally monitor surface soil moisture over land surfaces,
• globally monitor surface salinity over the oceans, and
• improve the characterisation of ice and snow covered surfaces.

In order to:

• advance climatological, oceanographic, meteorological, hydrological, agronomical, and glaciological science, and
• assess the potential of such measurements to contribute to improving the management of water resources.

For soil moisture:

Moisture is a measure of the amount of water within a given volume of material and is usually expressed as a percentage. From space, the SMOS instrument can measure as little as 4% moisture in soil on the surface of the Earch - which is about the same as being able to detect less than one teaspoonful of water mixed into a handful of dry soil.

• accuracy of 4% volumetric soil moisture
• spatial resolution 35-50 km
• revisit time 1-3 days

For ocean salinity:

Salinity describes the concentration of dissolved salts in water. It measures in practical salinity units (psu), which expresses a conductivity ratio. The average salinity of the oceans is 35 psu, which is equivalent to 35 grams of salt in 1 litre of water. SMOS aims to observe salinty down to 0.1 psu (averaged over 10-30 days and an area of 200 km x 200 km) - which is about the same as detecting 0.1 gram of salt in a litre of water.

• accuracy of 0.5-1.5 practical salinity units (psu) for a single observation
• accuracy of 0.1 psu for a 10-30 day average for an open ocean area of 200 km x 200 km