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New maps of salinity reveal the impact of climate variability on oceans
Since the saltiness of ocean surface waters is a key variable in the climate system, understanding how this changes is important.

blue arrow Mission Overview


The Soil Moisture and Ocean Salinity (SMOS) mission, launched on 2 November 2009, is one of the European Space Agency's Earth Explorer missions, which form the science and research element of the Living Planet Programme.

It is the first mission to provide, from microwave L-band measurements, global observations of variability in soil moisture and sea surface salinity due to continuous exchange in Earth's water cycle between the oceans, the atmosphere and the land. These key geophysical parameters, soil moisture for hydrology studies and salinity for enhanced understanding of ocean circulation, are both vital for climate change models.

Although designed as a five-year mission, the Programme Board for Earth Observation has recommended the approval of the extension of SMOS mission operations based on its excellent technical and scientific performance until end 2021 (and beyond). This enables enhanced analysis of longer-term process and new synergistic opportunities from new observing systems.

Mission Parameters
Orbit altitude Min 761.3 km
Max 788.4 km (height of elliptical orbit)
Orbit type LEO, sun-synchronous, polar, circular, dawn-dusk (LTAN 06:00)
Orbit inclination 98.42°
Repeat Cycle 149 days, 18 days sub-cycle

blue arrow Mission Objectives

The SMOS mission furthers our scientific knowledge of the Earth's water cycle, contributes to better weather and extreme-event forecasting, and helps improve climate models. SMOS also contributes significant information to cryospheric research.

blue arrow Instruments

The Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) is a passive microwave 2-D interferometric polarimetric radiometer.
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blue arrow Data

blue arrow DATA DOWNLOAD

Download SMOS data from the SMOS Online Dissemination Service. An EO-SSO account is required to access the service.
SMOS data is freely and openly available to everyone.

Direct download via HTTP or FTP


The following SMOS products are available:

  • SMOS baseline science products - The complete Level 1B/1C brightness temperature and Level 2 soil moisture and sea surface salinity datasets. These are the operational baseline products of the SMOS mission.
  • SMOS Near Real Time products - This includes the Level 1C brightness temperature "Light" product (in BUFR format) and the Level 2 soil moisture product generated using a Neural Network algorithm (in netCDF format), distributed by the SMOS ground segment in near real time i.e. respectively within three and four hours from sensing.
  • SMOS NRT Level 2 swath wind speed - SMOS retrieved surface wind speed gridded maps (with a spatial sampling of 1/4 x 1/4 degrees) are available in NetCDF format.
  • SMOS Level 3 daily wind speed - SMOS L3WS products are daily composite maps of the collected SMOS L2 swath wind products for a specific day, provided with the same grid than the Level 2 wind data (SMOS L2WS NRT) but separated into ascending and descending passes.
  • SMOS Level 3C Sea Ice Thickness - This data set contains daily estimations of SMOS retrieved sea-ice thickness and its uncertainty, at the edge of the Arctic Ocean during the period October-April and for Antarctica over the period April-October.
  • SMOS Soil Freeze and Thaw State - The SMOS Level 3 Freeze and Thaw (F/T) product provides daily information on the soil state in the Northern Hemisphere based on SMOS observations and associated ancillary data.
  • SMOS Tropical Cyclone Wind Radii fixes (WRF) - The SMOS WRF product is available in Near Real Time to support tropical cyclone forecasts.

Further information can be found in the data brochure.

blue arrow DATA TOOLS

A number of tools are available for visualising, processing and analysing SMOS data.

SMOS Toolbox

The SMOS Toolbox provides visualisation of Level-1C and Level-2 products in the Sentinel Application Platform (SNAP).


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The SMOS Data Viewer (SDV) provides a quick and easy way to view SMOS products and the auxiliary files used for generating Level-1 and Level-2 products.


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The SMOS Global Mapping Tool (GMT) is useful for plotting SMOS data into a single global geographical map. The GMT is also able to visualise additional quantities derived from SMOS data.

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SMOS NetCDF Conversion Tool

The SMOS NetCDF Conversion Tool is a self contained command line executable to be used for batch processing of large amounts of files.


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RWAPI can be used to extract information from Level-1 or Level-2 data files in Matlab, as it reads all products related to the retrieval of soil moisture as well as some auxiliary data used as input for the Level-2 processor.

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The SMOS Comparison Tool (SCoT) can be used to compare Level-1 SMOS products of the same type generated with the same schema version for the Data Blocks.

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The Earth Observation Swath and Orbit Visualisation tool (ESOV) can be used to view and select SMOS orbits, but it does not read any data products.


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blue arrow DATA QUALITY

SMOS data quality information covering monitoring of science and calibration products, providing monthly overviews of the health of MIRAS instrument and product quality, and any MIRAS instrument anomalies that may affect the quality of data acquired.

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blue arrow Cal/Val

Calibration and validation activities support the quality measures for SMOS data, by ensuring that the MIRAS instrument is performing well and to established baselines. Ongoing activities are conducted to support this process and reports are available which cover the status and any anomalies which may have occurred throughout the mission lifetime.

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