Minimize Scientific requirements

The principal objective of the SMOS mission is to provide maps of soil moisture and ocean salinity of specified accuracy, sensitivity, spatial resolution, spatial coverage and temporal coverage. In addition, the mission is expected to provide useful data for cryosphere studies.

In summary, the SMOS science objectives are to:

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

In order to:

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

Measurement goals

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 x 200 km