AIRS

AIRS
Name	Atmospheric Infrared Sounder
Acronym	AIRS
Operator	NASA / Jet Propulsion Laboratory
Launched	July 4, 2002
Platform	Aqua (satellite)
Mission type	Earth observation
Instrumentation	infrared sounder
Wavelength	infrared (3.7–15.4 µm)
Resolution	13.5 km nadir (at 705 km)
Status	operational (as of 2024)

AIRS The Atmospheric Infrared Sounder is a spaceborne hyperspectral instrument carried on the Aqua (satellite) mission, designed to obtain high-vertical-resolution profiles of atmospheric temperature and humidity and to monitor trace gases and surface properties. It was developed through a partnership including NASA, the Jet Propulsion Laboratory, and international contributors, and has contributed to fields spanning meteorology, climate science, and atmospheric chemistry by providing global, frequent infrared radiance measurements. AIRS data have been integrated into operational reanalysis, numerical weather prediction, and studies involving the El Niño–Southern Oscillation, Arctic amplification, and stratospheric composition variability.

Overview

AIRS operates as a grating spectrometer observing the thermal infrared and mid-infrared spectral bands to retrieve sounding information about the troposphere and lower stratosphere. The instrument complements microwave sounders such as the Advanced Microwave Sounding Unit and synergizes with other Aqua instruments including the Moderate Resolution Imaging Spectroradiometer, CloudSat, and CALIPSO for cloud and aerosol context. Designed to improve upon earlier hyperspectral systems like the Infrared Atmospheric Sounding Interferometer prototypes, AIRS has enabled improved operational forecasts at agencies such as the National Oceanic and Atmospheric Administration and scientific analyses at institutions like the European Centre for Medium-Range Weather Forecasts.

Instrumentation and Design

AIRS is a high-spectral-resolution grating spectrometer with 2378 spectral channels covering 3.7–15.4 µm, utilizing cryogenically cooled detectors and foreoptics engineered by teams at NASA Goddard Space Flight Center and the Jet Propulsion Laboratory. The optical train includes a scan mirror permitting a swath that yields near-global coverage every 24 hours from the Aqua (satellite) sun-synchronous orbit. The instrument was developed alongside the Advanced Microwave Sounding Unit to provide a combined retrieval capability: AIRS supplies infrared sensitivity to temperature and humidity profiles while microwave channels from AMSU provide cloud-clearing support. Engineering tradeoffs involved detector material choices informed by work at laboratories such as Lockheed Martin and procurement from industrial partners including Honeywell-affiliated subcontractors.

Data Products and Processing

AIRS produces radiance spectra, retrieved atmospheric temperature and water vapor profiles, cloud properties, and concentrations of gases such as carbon dioxide, ozone, methane, and carbon monoxide. Processing pipelines are maintained by the Goddard Earth Sciences Data and Information Services Center with algorithms developed by teams at Jet Propulsion Laboratory, University of Wisconsin–Madison, and California Institute of Technology. Level 1 products supply calibrated and geolocated radiances, while Level 2 provides geophysical parameters; Level 3 gridded monthly and daily composites support climate diagnostics at centers including the National Aeronautics and Space Administration climate modeling divisions. Radiative transfer models used in retrievals reference line databases and community models such as HITRAN and are validated against radiosonde networks like Integrated Global Radiosonde Archive and field campaigns led by National Center for Atmospheric Research.

Scientific Applications

AIRS data underpin research in atmospheric dynamics, trace gas transport, and surface temperature variability. Studies leveraging AIRS have advanced understanding of El Niño–Southern Oscillation teleconnections, moisture transport associated with the Asian monsoon system, and trends pertinent to Anthropogenic climate change. The instrument has been used to monitor wildfire emissions affecting ozone and carbon monoxide columns, studies of stratosphere–troposphere exchange linked to the Antarctic ozone hole, and assimilation experiments at centers such as European Centre for Medium-Range Weather Forecasts and NOAA National Centers for Environmental Prediction. AIRS observations have also supported validation and intercomparison activities with instruments like Infrared Atmospheric Sounding Interferometer and satellite missions including Suomi NPP and Sentinel-5 Precursor for continuity of infrared sounding records.

Mission History and Operations

AIRS was launched aboard Aqua (satellite) on July 4, 2002, as part of the NASA Earth Observing System. Post-launch commissioning involved calibration and algorithm tuning in collaboration with science teams from Jet Propulsion Laboratory and the international science community. Over its multi-decadal operation AIRS has undergone software updates, product reprocessing cycles, and intercalibration efforts with missions such as AIRS successor studies and international instruments flown by European Space Agency missions. Operational use expanded into the forecasting pipeline at agencies like NOAA and was incorporated into reanalysis datasets produced by NASA and ECMWF.

Calibration and Validation

AIRS radiometric and wavelength calibration relied on on-board blackbody views, deep-space observations, and vicarious validation using the AERONET sunphotometer network, radiosondes from Integrated Global Radiosonde Archive, and field campaigns coordinated with National Center for Atmospheric Research and university partners. Validation studies compared AIRS retrievals against lidar, microwave sounder, and in situ measurements to quantify biases and uncertainties; results guided algorithm revisions executed by teams at Jet Propulsion Laboratory and NASA Goddard Space Flight Center. Intercalibration with instruments on missions such as MetOp and Suomi NPP ensured continuity across the satellite observing system, supporting long-term climate records used by panels like the Intergovernmental Panel on Climate Change.

Category:Earth observation instruments