AVHRR

AVHRR
NASA · Public domain · source
Name	AVHRR
Other names	Advanced Very High Resolution Radiometer
Operator	National Oceanic and Atmospheric Administration; European Organisation for the Exploitation of Meteorological Satellites; Russian Federal Service for Hydrometeorology and Environmental Monitoring
Mission type	Earth observation; meteorology; climatology
Mass	70–120 kg (varies by platform)
Power	50–150 W (approximate)
Spectral bands	Visible, near-infrared, thermal infrared
Spatial resolution	~1.1 km (nadir)
Launched	1978–present (series)
Instruments onboard	scanning radiometer
Status	In service on multiple polar-orbiting platforms

AVHRR

AVHRR is a spaceborne scanning radiometer series designed for global meteorology, oceanography, and land surface monitoring that provided continuity between early NOAA polar platforms and later international systems. The instrument supported long-term records used by agencies such as National Aeronautics and Space Administration, European Space Agency, and Japan Meteorological Agency for operational forecasting, climate research, and environmental change studies. AVHRR data underpin analyses by research centers including National Center for Atmospheric Research, Godard Space Flight Center, and Hadley Centre.

Overview

The AVHRR family comprises cross-track scanning radiometers flown on polar-orbiting satellites like NOAA-6, NOAA-19, and the MetOp series, providing multi-spectral imagery across visible and infrared channels for global coverage. Designed during collaborations among National Environmental Satellite Data and Information Service, United States Department of Commerce, and international partners including EUMETSAT and Russian Federal Space Agency, AVHRR established systematic records for sea surface temperature, vegetation indices, and cloud detection. The instrument's role intersects major observational programs such as Global Climate Observing System, International Geosphere-Biosphere Programme, and Group on Earth Observations.

Instrument Design and Specifications

AVHRR is a passive, cross-track scanning radiometer using rotating scan mirrors and cooled detectors to measure radiance in discrete bands. Earlier generations had 4 channels while later variants added a 5th channel for enhanced thermal separation; spectral characteristics align with standards used by MODIS on Terra and VIIRS on Suomi National Polar-orbiting Partnership. Typical specifications include a nadir spatial resolution near 1.1 km, swath widths around 2,700 km enabling near-global twice-daily coverage from sunsynchronous polar orbits like those of NOAA-19 and MetOp-A. Onboard electronics derive calibrated counts which are converted to radiances and brightness temperatures using preflight radiometric characterizations tied to facilities such as National Institute of Standards and Technology and verification campaigns with instruments from Jet Propulsion Laboratory.

Data Products and Processing

AVHRR processing chains generate Level 1 calibrated radiances, Level 2 geophysical variables (e.g., sea surface temperature, cloud masks), and higher-level products like normalized difference vegetation index (NDVI) and land surface temperature. Operational processing centers include NOAA CLASS, EUMETSAT Metop Ground Segment, and regional data hubs tied to Goddard Earth Sciences Data and Information Services Center and PANGEA. Algorithms implement atmospheric correction and cloud screening procedures developed by teams at University of Maryland, University of Exeter, and CSIR laboratories, often cross-comparing with microwave sensors on ASCAT and scatterometer missions. Reprocessing efforts to create Climate Data Records are coordinated with National Climatic Data Center initiatives and global archives maintained by Committee on Earth Observation Satellites participants.

Applications and Uses

AVHRR-derived datasets support operational weather forecasting at centers like European Centre for Medium-Range Weather Forecasts and National Weather Service, oceanographic analyses at NOAA National Ocean Service, and ecological monitoring by groups such as World Wildlife Fund and Conservation International. Long-term series enable trend detection for sea surface temperature anomalies related to El Niño–Southern Oscillation, land cover change analyses used in studies by NASA Jet Propulsion Laboratory and Woods Hole Oceanographic Institution, and agricultural monitoring applied by Food and Agriculture Organization. Disaster response teams from International Federation of Red Cross and Red Crescent Societies and United Nations Office for the Coordination of Humanitarian Affairs have used AVHRR imagery for wildfire, flood, and volcanic ash mapping.

Calibration and Validation

Calibration strategies combine on-ground preflight characterization, onboard calibration using space and internal references, and vicarious validation against in situ networks such as Argo, Drifting Buoy, and global radiosonde arrays coordinated by World Meteorological Organization. Intercomparisons with contemporary satellite instruments—MODIS, VIIRS, and instruments on Envisat—support bias assessments and time series homogenization performed by research groups at NOAA/STAR and University of Colorado Boulder. Field campaigns collaborating with institutions like Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory provide matchup data for radiometric and geolocation accuracy improvements.

Operational History and Satellite Platforms

Deployed continuously since the late 1970s, AVHRR has flown on NOAA polar satellites (e.g., NOAA-7, NOAA-9, NOAA-15, NOAA-18, NOAA-19), on MetOp-A, MetOp-B, and on select international platforms supporting bilateral programs with Russian Meteor-M series. The data record has been maintained through successive instrument upgrades, operational transitions managed by NOAA NESDIS and EUMETSAT, and reprocessing initiatives to produce homogeneous climate records used by the Intergovernmental Panel on Climate Change and national climate services. Continued legacy utility informs the design of successor sensors and contributes to multi-decadal Earth system observing strategies championed by Group on Earth Observations.

Category:Satellite remote sensing instruments