SMOS

SMOS
Name	Soil Moisture and Ocean Salinity (SMOS)
Operator	European Space Agency
Mission type	Earth observation
Launch date	2 November 2009
Launch site	Guiana Space Centre
Orbit type	Sun-synchronous orbit
Instruments	Microwave Imaging Radiometer using Aperture Synthesis (MIRAS)
Mass	~660 kg
Status	Operational

SMOS is a European Space Agency Earth observation satellite mission designed to provide global measurements of surface soil moisture and ocean salinity using passive microwave radiometry. Developed by the European Space Agency in partnership with national space agencies and research institutions, the mission addresses key needs in hydrology, oceanography, climate science, and weather prediction. SMOS data have supported studies ranging from water cycle variability to carbon fluxes and have been assimilated into operational models developed by international meteorological and hydrological centers.

Overview

SMOS was conceived during discussions within the European Space Agency strategic programs and emerged from collaborations among national agencies such as the Centre National d'Études Spatiales, the Instituto Nacional de Técnica Aeroespacial, and industry partners like Thales Alenia Space and EADS Astrium. Launched from the Guiana Space Centre aboard a Rockot/Dnepr-class vehicle, the spacecraft operates in a sun-synchronous orbit optimized for repeated global coverage. The mission uses an L-band radiometer and a novel two-dimensional synthetic aperture concept to achieve wide swath imaging, meeting requirements set by climate initiatives and programs such as the Global Climate Observing System and the Committee on Earth Observation Satellites.

Mission Objectives

Primary objectives include retrieval of global surface soil moisture patterns and sea surface salinity at a spatial and temporal resolution suitable for climate and hydrological studies. The mission aims to improve understanding of land–atmosphere interactions relevant to organizations like European Centre for Medium-Range Weather Forecasts and National Oceanic and Atmospheric Administration modeling centers, and to provide observational constraints for assimilation systems used by the Met Office and the Japan Meteorological Agency. Secondary objectives encompass cryosphere and freeze–thaw state monitoring relevant to work by the National Snow and Ice Data Center and contributions to disaster management frameworks such as those coordinated by the United Nations Office for Disaster Risk Reduction.

Spacecraft and Instruments

The payload centers on the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), a two-dimensional interferometric radiometer operating in the L-band (~1.4 GHz). MIRAS employs an array of antenna elements mounted on a deployable boom structure developed with industrial partners including Alcatel Space and OHB System. The instrument design was influenced by concepts explored in missions associated with the European Space Research and Technology Centre and laboratory programs at institutions like the Institut d'Astrophysique Spatiale. MIRAS provides multi-incidence angle brightness temperature measurements across swaths of several hundred kilometers, enabling retrieval algorithms developed in collaboration with researchers at the Institut National de la Recherche Agronomique and the Barcelona Supercomputing Center.

Data Products and Processing

SMOS data processing produces Level 1 brightness temperature maps and Level 2 geophysical products including soil moisture and sea surface salinity. Algorithm development has involved research centers such as the European Centre for Medium-Range Weather Forecasts, the National Aeronautics and Space Administration, and the French Alternative Energies and Atomic Energy Commission for calibration and radio-frequency interference mitigation. The processing chain runs at ground segments operated by agencies including the European Space Operations Centre and national data centers like the Pôle ORFEO and the Spanish Centre for Earth Observation. Products comply with formats accepted by programs such as the Group on Earth Observations and are made available to communities including the World Climate Research Programme and regional hydrological services.

Applications and Scientific Impact

SMOS products have been used in studies involving the Global Precipitation Measurement initiative, evapotranspiration estimates in collaboration with teams at the United States Geological Survey, and drought monitoring efforts tied to Food and Agriculture Organization programs. Ocean salinity observations contribute to research on thermohaline circulation relevant to the Argo float network and studies involving the World Ocean Circulation Experiment. SMOS-derived soil moisture has enhanced flood forecasting models used by river basin authorities such as the International Commission for the Protection of the Rhine and supported agricultural monitoring in partnership with the European Commission's Copernicus services. Peer-reviewed work by groups at institutions like the Max Planck Institute for Meteorology and the Woods Hole Oceanographic Institution demonstrates impacts on carbon cycle and climate model evaluation.

Mission Operations and History

After launch, early operations involved commissioning phases managed by the European Space Operations Centre and calibration campaigns with teams from the European Space Agency and national research institutes. The mission overcame challenges including radio-frequency interference and instrument calibration drifts addressed through coordinated campaigns with agencies like the International Telecommunication Union and research groups at the National Institute for Space Research (INPE). Operational lifetime has extended beyond its nominal design through engineering efforts comparable to those that sustained missions such as Envisat and SMAP, with ongoing science operations and reprocessing activities supporting long-term climate records.

International Collaboration and Management

SMOS is managed by the European Space Agency with strong contributions from member states and international partners including the National Aeronautics and Space Administration, the National Research Council (Italy), and the Swiss Space Office. Scientific advisory roles involve consortia of universities and institutions such as University of Valencia, University of Reading, and Institut Polytechnique de Paris. Data distribution and user support engage global networks including the Global Earth Observation System of Systems and regional centers linked to the Group on Earth Observations to ensure uptake by operational services and research programs.

Category:European Space Agency satellites Category:Earth observation satellites