IASI

IASI
Name	IASI
Mission type	Atmospheric sounding
Operator	CNES, EUMETSAT
Manufacturer	Airbus Defence and Space, CNES
Launch mass	~280 kg
Power	~250 W
Launch date	2006–2014 (series)
Orbit	Sun-synchronous
Instruments	Infrared Fourier Transform Spectrometer

IASI

IASI is a spaceborne infrared atmospheric sounding instrument flown on polar-orbiting meteorological satellites. It provides high-spectral-resolution measurements of thermal infrared radiation used for atmospheric temperature, humidity, and trace gas retrievals supporting operational ECMWF analyses, WMO services, and research by institutions such as NASA, NOAA, and Met Office. The program is governed through partnerships between CNES and EUMETSAT and flies on the Metop series of satellites operated in cooperation with ESA programmes.

Overview

IASI was conceived to advance atmospheric sounding capabilities first demonstrated by instruments like IASI's predecessors within international efforts including NOAA-14 and ERS-2. The instrument performs high-resolution interferometric sounding analogous to laboratory Fourier transform spectrometers used at facilities such as JPL, LMD, and Laboratoire de Physique de l'Atmosphère. Flight models were integrated into the Metop-A, Metop-B, and Metop-C platforms, which follow polar sun-synchronous orbits coordinated with programmes like Suomi NPP and NOAA-20 to improve temporal coverage for global monitoring and assimilation into systems run by ECMWF, Météo-France, and Deutscher Wetterdienst.

Instrument Design and Technology

The IASI instrument is a cooled infrared Fourier Transform Spectrometer coupled with a broadband infrared imager. Its design draws on heritage from laboratory interferometers at CNES and industrial experience at Airbus Defence and Space and subcontractors such as Thales Alenia Space. Key components include a Michelson interferometer, cryogenic detectors cooled by passive and active systems similar to those used on AIRS and TES, and a pointing mechanism aligned to the Metop payload module. Spectral coverage spans strong and weak molecular bands enabling retrievals of gases like Ozone, Carbon dioxide, Methane, Nitrous oxide, and water vapour, while radiometric calibration relies on on-board blackbodies and views of deep space analogous to calibration approaches used on MOPITT and SCIAMACHY.

Mission Operations and Data Processing

Operations are jointly managed by CNES for instrument stewardship and EUMETSAT for data distribution and operational service. Raw interferograms are downlinked to ground stations such as Kiruna Space Observatory and processed through level-0 to level-2 chains implemented at processing centres including EUMETSAT’s central facility and partner sites like LMD and NOAA laboratories. Processing pipelines perform apodization, radiometric correction, and transform to spectral radiances followed by retrieval algorithms developed by teams at LSCE, ULB, and University of Oxford that produce temperature and humidity profiles and trace gas columns. Data streams are archived and disseminated via operational portals used by ECMWF, Copernicus services, and national meteorological services.

Scientific Applications and Products

IASI products serve meteorological forecasting, climate monitoring, air quality, and emergency response. Operational products include retrieved atmospheric temperature profiles, humidity profiles, and surface temperature used in numerical weather prediction at ECMWF and UK Met Office. Climate-oriented products track long-term trends in greenhouse gases such as CO2 and CH4 comparable to records from OCO-2 and GOSAT. Air quality and chemistry applications exploit IASI’s sensitivity to pollutants like NO2, SO2, and carbon monoxide measured alongside observations from OMI and TROPOMI to inform agencies including European Environment Agency. IASI data also facilitate volcanic ash detection relevant to ICAO advisories, and wildfire plume monitoring alongside sensors such as VIIRS and MODIS.

Performance and Validation

Performance assessments compare IASI radiances and retrievals with reference measurements from radiosondes, ground-based FTIR networks like NDACC, and aircraft campaigns such as MOZAIC and IAGOS. Validation studies led by groups at LSCE, CNES, EUMETSAT, and Met Office demonstrate radiometric stability, spectral calibration accuracy, and retrieval precisions that meet or exceed design requirements for operational assimilation. Intercomparisons with instruments like AIRS, CrIS, and TES quantify biases and spectral residuals; mitigation efforts include refined instrument line shape characterization and improved forward radiative transfer from models maintained at LAM and AER.

Historical Development and Future Perspectives

The IASI programme evolved from early proposals in the 1980s and 1990s and benefited from collaborations among CNES, EUMETSAT, and industrial partners during the EUMETSAT Polar System planning. The successive Metop launches established a long-term data record supporting continuity into successor missions coordinated with EUMETSAT Polar System Second Generation and research missions such as EPS-SG and concepts explored by ESA and NASA. Future enhancements focus on higher spectral resolution, improved hyperspectral imagers inspired by TROPOMI and CrIS developments, and integration with constellation strategies pursued by Copernicus and national agencies to bolster diurnal coverage and climate monitoring capabilities.

Category:Spacecraft instruments