SMOS, Studying the Earth’s salt and water

Studying the Earth’s salt and water

  • European Space Agency mission
  • In development
  • Scheduled for launch end of 2008
SMOS (Soil Moisture and Ocean Salinity) will make global observations of the Earth’s surface soil water content and the salt in the oceans. Both are linked to the Earth’s climate and water cycle. A greater understanding of soil moisture and ocean salinity will lead to better forecasting of weather and extreme-weather events.

Soil moisture and humidity are connected. If soil becomes dry, due to drought, then less water evaporates into our atmosphere. More moisture raises humidity and also lowers temperatures.

The salinity of the sea affects ocean currents. The salt content varies due to the addition or removal of fresh water through evaporation and rain and from melting ice in polar regions.

SMOS is the second Earth Explorer Opportunity mission and is part of ESA’s (European Space Agency) Living Planet Programme. Its data will contribute to seasonal climate forecasting and will also help studies of regions of snow and ice.

For more information, visit the ESA website.

Mission facts

  • SMOS will be launched on a modified Russian Intercontinental Ballistic Missile.

  • Its main instrument MIRAS (Microwave Imaging Radiometer using Aperture Synthesis) can measure as little as 4 per cent soil moisture from space.

  • The satellite will be able to make observations over a hexagonal area of almost 1,000 km across.

  • SMOS will be able to achieve global coverage every three days.


MIRAS is a new type of instrument that can observe both soil moisture and ocean salinity by imaging emitted microwave radiation at a frequency of around 1.4 GHz.

The Y-shaped antenna on MIRAS has 69 small receivers – 23 on each arm.

A 2-D measurement image will be taken every 1.2 seconds.

UK involvement

SciSys UK Limited is a member of the SMOS Payload Module Team and developed the on board software that controls one of the instruments. ComDev developed the X-band filter while Chelton Antennas was involved in the manufacture of the antennas.

Two Principal Investigators involved in SMOS are from the National Oceanographic Centre, Southampton and De Monfort University’s Earth and Planetary Remote Sensing Laboratory, Leicester.

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