# MIRAS
*sensor . products*

Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), the sole payload on ESA's SMOS mission. A 2-D interferometric passive radiometer operating at L-band 1.413 GHz with a Y-shaped array of 69 LICEF antenna receivers spanning an 8 m diameter. Reconstructs brightness temperature fields interferometrically to retrieve global soil moisture and sea surface salinity.

## Specifications
- **manufacturer**: eads-casa-espacio
- **product status**: operational
- **deployment context**: orbital
- **sensor**: {"instrument_family":"radiometer","measurement_principle":"passive","frequency_bands_ghz":[1.413],"polarisation_modes":["H","V","H+V (full polarimetry)"],"scan_type":"synthetic-aperture-interferometric","swath_km":1050,"resolution_per_band_km":[{"frequency_ghz":1.413,"footprint_km":"35-50"}],"radiometric_sensitivity_k":3.5,"notes":"MIRAS consists of a central hub plus 3 deployable arms arranged in a Y-shape, total span 8 m. Each arm and the hub carry LICEF (Lightweight Cost-Effective Front-end) receivers totalling 69 antennas. Aperture-synthesis principle cross-correlates all receiver pairs to reconstruct brightness temperature field. Radiometric sensitivity 3.5 K rms at boresight, 5.8 K rms at swath edge (Level-1). Spatial resolution 35-50 km depending on position in swath; resampled to 15 km grid. Swath hexagonal footprint ~1050 km enabling 3-day global revisit at equator. Operates in dual-polarisation (all H or all V) or full-polarisation mode. Absolute accuracy 2.6 K (RMS 1.6-4 K depending on scene and swath position). Built under ESA contract by EADS-CASA Espacio (Spain) leading a >20-company European consortium. SMOS launched November 2009; MIRAS operational continuously since December 2009."}
- **entity type**: sensor
- **last verified date**: 2026-06-05
- **verified by**: agency-doc
- **claim status**: agency-sourced
- **provider**: eads-casa-espacio
- **attributes**: {"kind":"sensor","manufacturer":"eads-casa-espacio","description":"Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), the sole payload on ESA's SMOS mission. A 2-D interferometric passive radiometer operating at L-band 1.413 GHz with a Y-shaped array of 69 LICEF antenna receivers spanning an 8 m diameter. Reconstructs brightness temperature fields interferometrically to retrieve global soil moisture and sea surface salinity.","product_status":"operational","deployment_context":"orbital","sensor":"{\"instrument_family\":\"radiometer\",\"measurement_principle\":\"passive\",\"frequency_bands_ghz\":[1.413],\"polarisation_modes\":[\"H\",\"V\",\"H+V (full polarimetry)\"],\"scan_type\":\"synthetic-aperture-interferometric\",\"swath_km\":1050,\"resolution_per_band_km\":[{\"frequency_ghz\":1.413,\"footprint_km\":\"35-50\"}],\"radiometric_sensitivity_k\":3.5,\"notes\":\"MIRAS consists of a central hub plus 3 deployable arms arranged in a Y-shape, total span 8 m. Each arm and the hub carry LICEF (Lightweight Cost-Effective Front-end) receivers totalling 69 antennas. Aperture-synthesis principle cross-correlates all receiver pairs to reconstruct brightness temperature field. Radiometric sensitivity 3.5 K rms at boresight, 5.8 K rms at swath edge (Level-1). Spatial resolution 35-50 km depending on position in swath; resampled to 15 km grid. Swath hexagonal footprint ~1050 km enabling 3-day global revisit at equator. Operates in dual-polarisation (all H or all V) or full-polarisation mode. Absolute accuracy 2.6 K (RMS 1.6-4 K depending on scene and swath position). Built under ESA contract by EADS-CASA Espacio (Spain) leading a >20-company European consortium. SMOS launched November 2009; MIRAS operational continuously since December 2009.\"}"}
- **technology**: microwave-radiometry

## Editorial
MIRAS (Microwave Imaging Radiometer using Aperture Synthesis) is the sole payload on ESA's Soil Moisture and Ocean Salinity (SMOS) spacecraft. It is a 2-D interferometric passive microwave radiometer operating at L-band (1.413 GHz). ESA describes MIRAS as the first satellite instrument to apply aperture-synthesis imaging at L-band from orbit [^esa-smos].

The instrument uses a Y-shaped array of 69 LICEF (Lightweight Cost-Effective Front-end) receivers arranged on a central hub and three deployable arms, spanning a total diameter of approximately 8 metres [^esa-miras]. Rather than mechanically scanning a real aperture, MIRAS cross-correlates the signals received by all receiver pairs simultaneously to reconstruct a brightness temperature field across a hexagonal snapshot footprint. This aperture-synthesis approach achieves spatial resolution of 35 to 50 km [^esa-miras] across a swath of approximately 1050 km [^esa-miras], enabling 3-day global revisit at the equator [^esa-miras].

The instrument operates in dual-polarisation mode (all-H or all-V) or full-polarisation mode [^esa-miras]. eoPortal reports radiometric sensitivity at boresight of 3.5 K rms (Level-1 brightness temperature), degrading to 5.8 K rms at the swath edge, with absolute accuracy of 2.6 K rms and scene- and position-dependent variation of 1.6 to 4 K [^eoportal-smos].

MIRAS was built under ESA contract by EADS-CASA Espacio (Spain) as prime, leading a consortium of more than 20 European companies [^esa-eads-contract]. SMOS launched in November 2009 and MIRAS has been in continuous operation since December 2009 [^esa-miras]. Primary geophysical products are global surface soil moisture and sea surface salinity, both retrieved from L-band brightness temperature.

## Compositional position
- smos (missions) --[mission_payloads]--> MIRAS

## Sources
- [eoportal-smos] | SMOS (Soil Moisture and Ocean Salinity) Mission - eoPortal | https://www.eoportal.org/satellite-missions/smos | tier=community | accessed=2026-06-05
- [esa-miras] | MIRAS - ESA Earth Online | https://earth.esa.int/eogateway/instruments/miras | tier=agency-doc | accessed=2026-06-05
- [esa-smos] | SMOS Novel Technology - ESA | https://www.esa.int/Applications/Observing_the_Earth/SMOS/Novel_technology | tier=agency-doc | accessed=2026-06-05
- [esa-eads-contract] | ESA and EADS-CASA sign contract to build instrument for the SMOS mission | https://www.esa.int/About_Us/Business_with_ESA/ESA_and_EADS-CASA_sign_contract_to_build_instrument_for_the_SMOS_mission | tier=agency-doc | accessed=2026-06-05
- [eohandbook-miras] | CEOS Instrument Summary - MIRAS (SMOS) | https://database.eohandbook.com/database/instrumentsummary.aspx?instrumentID=689 | tier=community | accessed=2026-06-05

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Source: https://eo-atlas.org/products/sensor/miras
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