SMOS (satellite)

SMOS (satellite)
Name	SMOS
Operator	European Space Agency
Mission type	Earth observation
Spacecraft bus	Minisatellite
Launch date	2009-11-02
Launch vehicle	Rockot
Launch site	Plestsk Cosmodrome
Orbit type	Sun-synchronous orbit
Instruments	Microwave Imaging Radiometer using Aperture Synthesis

SMOS (satellite) SMOS is an Earth observation satellite developed by the European Space Agency in partnership with the Centre National d'Études Spatiales, the Institut national de l'information géographique et forestière, and numerous European research institutions. Designed to provide global measurements of soil moisture and sea surface salinity, SMOS carries a novel interferometric radiometer to address scientific objectives relevant to the World Climate Research Programme, Intergovernmental Panel on Climate Change, and operational services such as Copernicus Programme. The mission supports applications in hydrology, oceanography, and climate by delivering L-band microwave brightness temperature observations.

Overview

SMOS was initiated under ESA's Earth Explorer Opportunity Missions framework with contributions from national agencies including CNES, DLR, and ISRO partner science teams, aiming to demonstrate new remote sensing capabilities for the European Space Agency's Earth observation strategy. The spacecraft implements an aperture synthesis radiometer concept developed by European laboratories such as Institut d'électronique et de télécommunications de Rennes and tested in experiments involving the European Space Research and Technology Centre. SMOS operates in the L-band at 1.4 GHz, exploiting a protected frequency allocated by the International Telecommunication Union for passive microwave sensing.

Mission Objectives

Primary objectives include retrieval of global surface soil moisture with spatial resolution suitable for land-surface models used in the Global Energy and Water Exchanges project and monitoring of sea surface salinity for studies of the global water cycle and ocean circulation features like the Gulf Stream and El Niño–Southern Oscillation. The mission supports validation campaigns involving institutions such as European Centre for Medium-Range Weather Forecasts, NASA, NOAA, and national hydrological services. Ancillary goals encompass characterizing sea ice thickness, wetland inundation, and freeze–thaw state for polar studies tied to Arctic Council science initiatives.

Spacecraft and Instruments

The SMOS payload is the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), conceived by a consortium coordinated by European Space Agency contractors and research teams at Institut de mécanique des fluides de Toulouse and Universidad Politécnica de Madrid. MIRAS features a deployable planar array of deployable Y-shaped antennas forming a synthetic aperture interferometer, enabling wide swath imaging without a large parabolic reflector. Onboard subsystems include attitude control by reaction wheels and star trackers from SENER, thermal control systems developed with Thales Alenia Space, and data handling processors designed with support from Airbus Defence and Space. The instrument measures Stokes parameters of L-band brightness temperature to infer geophysical variables.

Launch and Orbit

SMOS was launched on 2 November 2009 aboard a Russian Rockot launch vehicle from Plestsk Cosmodrome into a 758 km sun-synchronous dawn-dusk orbit, providing global coverage every three days with a 645 km swath. The orbit configuration was chosen to align local overpass times with diurnal cycles relevant to retrieval algorithms used by teams at University of Valencia, Institut Pierre-Simon Laplace, and University of Leicester. Post-launch commissioning involved orbit control maneuvers coordinated with European Space Operations Centre and instrument calibration campaigns linking ground sites such as the AUSTRALIAN Bureau of Meteorology testbeds and SMOS Valencia site.

Data Processing and Products

SMOS data are processed through ESA's Level 0–2 processing chain at the European Space Agency's payload data ground segment with algorithms developed by the SMOS Barcelona Expert Centre and the European Space Agency's Earth Observation Directorate. Level 1 products provide calibrated brightness temperatures; Level 2 delivers geophysical retrievals including soil moisture and sea surface salinity with associated uncertainty estimates. Processing algorithms incorporate radiative transfer models validated by campaigns with European Centre for Medium-Range Weather Forecasts, National Oceanography Centre, and CSIRO. Data dissemination leverages the Copernicus Open Access Hub and research portals used by the World Meteorological Organization and academic partners.

Scientific Results and Applications

SMOS has contributed to improved characterization of continental water storage, enhancing seasonal forecasts by groups at Centre National de Recherches Météorologiques and informing drought monitoring systems used by the Food and Agriculture Organization. In oceanography, SMOS salinity maps revealed mesoscale variability associated with the Atlantic Meridional Overturning Circulation and freshwater plumes from the Amazon River, supporting studies by Scripps Institution of Oceanography and Plymouth Marine Laboratory. Polar science teams from Alfred Wegener Institute and University of Alaska Fairbanks used SMOS brightness temperatures to infer sea ice thickness trends and freeze–thaw dynamics relevant to Arctic Council assessments. Multi-sensor synergy combining SMOS with Soil Moisture Active Passive, Jason, and GRACE missions improved hydrological model constraints and validation for the Global Precipitation Measurement community.

Mission Operations and Status

Operational oversight is conducted by ESA's Earth Observation Programme with mission management interfaces involving CNES and national operator teams; routine calibration and validation are coordinated with international partners including NASA and NOAA. After more than a decade in orbit, SMOS continues to provide research-quality L-band observations while facing instrument degradation challenges typical of long-duration missions; mitigation measures include algorithm updates from research centers like University of Barcelona and hardware mode adjustments executed from the European Space Operations Centre. SMOS legacy informs follow-on missions and proposals within the ESA Living Planet Programme and contributes datasets to ongoing climate and operational services.

Category:Earth observation satellites of the European Space Agency