CEOS EO HANDBOOK – MEASUREMENT INSTRUMENTS
Measurements > Atmosphere >
Aerosols >
Aerosol optical depth (column/profile)


Measurement Definition*: The aerosol optical depth or optical thickness (τ) is defined as the integrated extinction coefficient over a vertical column of unit cross section.

Thematic Links
InstrumentStatus/
Accuracy
Instrument DescriptionMeasurement TechnologyTimeline
ABI
Advanced Baseline Imager
Operational
Detects clouds, cloud properties, water vapour, land and sea surface temperatures, dust, aerosols, volcanic ash, fires, total ozone, snow and ice cover, vegetation index.Multi-purpose imaging Vis/IR radiometer
ACDL
Aerosol and Carbon Detection Lidar
Operational
For CO2 a pulsed dual-wavelength lidar alternately emits two pulsed lasers near 1572 nm in a sequential manner one in the CO2 absorption line and one off the line. For aerosol detection a high spectral resolution lidar (HSRL) at 532 and 1064 nm.Atmospheric lidar
Advanced GOCI
Advanced Geostationary Ocean Colour Imager
Operational
Ocean colour information, coastal zone monitoring, land resources monitoring.Multi-purpose imaging Vis/IR radiometer
AHI
Advanced Himawari Imager
Operational
Measures cloud cover, cloud motion, cloud height, cloud properties, water vapour, rainfalll, sea surface temperatures and Earth radiation, dust, aerosols, volcanic ash, fires, snow and ice cover.Multi-purpose imaging Vis/IR radiometer
AMI
Advanced Meteorological Imager
Operational
Continuous monitoring capability for the near real-time generation of high-resolution meteorological products and long-term change analysis of land/sea surface temperature and cloud coverage.Multi-purpose imaging Vis/IR radiometer
AVHRR/3
Advanced Very High Resolution Radiometer/3
Operational
Measurements of land and sea surface temperature, cloud cover, snow and ice cover, soil moisture and vegetation indices. Data also used for volcanic eruption monitoring.Multi-purpose imaging Vis/IR radiometer
DPC-2
Directional Polarization Camera - 2
Operational
To measure aerosol and cloud microphysical parameters and the Bidirectional Reflectance Distribution Function (BRDF)n/a
EPIC
Earth Polychromatic Imaging Camera
Operational
+/-1 %
Diurnal measurements of ozone, sulfur dioxide, UV surface radiation, clouds, aerosols and vegetation.Multi-purpose imaging Vis/IR radiometer
GNSS POD Receiver
Global Navigation Satellite Systems (GNSS) Precise Orbit Determination (POD) Receiver
Operational
Precision orbit determination.n/a
GOME-2
Global Ozone Monitoring Experiment - 2
Operational
Measurement of total column amounts and stratospheric and tropospheric profiles of ozone. Also amounts of H20, NO2, OClO, BrO, SO2 and HCHO.High-resolution nadir-scanning SW spectrometer
MISR
Multi-angle Imaging SpectroRadiometer
Operational
Measurements of global surface albedo, aerosol and vegetation properties. Also provides multi-angle bidirectional data (1% angle-to-angle accuracy) for cloud cover and reflectances at the surface and aerosol opacities. Global and local modes.Multi-channel/direction/polarisation radiometer
MODIS
MODerate-Resolution Imaging Spectroradiometer
Operational
Data on biological and physical processes on the surface of the Earth and in the lower atmosphere, and on global dynamics. Surface temperatures of land and ocean, chlorophyll fluorescence, land cover measurements, cloud cover (day and night).n/a
MSU-MR
Low-resolution multispectral scanning imager-radiometer
Operational
Parameters of clouds, snow, ice and land cover, vegetation, surface temperature, fire detection.Multi-purpose imaging Vis/IR radiometer
NACHOS Hyperspectral Imager
NACHOS Hyperspectral Imager
Operational
 High-resolution nadir-scanning SW spectrometer
OLCI
Ocean and Land Colour Imager
Operational
Marine and land services.n/a
OMI
Ozone Measuring Instrument
Operational
Mapping of ozone columns, key air quality components (NO2, SO2, BrO, OClO and aerosols), measurements of cloud pressure and coverage, global distribution and trends in UV-B radiation.High-resolution nadir-scanning SW spectrometer
OMPS
Ozone Mapping and Profiler Suite
Operational
Measures total amount of ozone in the atmosphere and the ozone concentration variation with altitude.High-resolution nadir-scanning SW spectrometer
SGLI
Second-generation Global Imager
Operational
+/-0.15
Medium resolution multi-spectral imaging of land, ocean and atmosphere. SGLI-VNR is an optical sensor capable of multi-channel nadir observation at wavelengths from near-UV to NIR and forward or backward polarization observation at red and near infrared wavelengths (Push-broom scanning). SGLI-IRS is an optical sensor capable of multi-channel nadir observation at wavelengths from SWIR to TIR wavelengths (Cross-track scanning).n/a
SPEXone
Spectro-Polarimeter for Exploration
Operational
Polarimeter for measuring aerosol optical properties, clouds and aerosol types. Multi-angle spectro-polarimetry by spectral modulation technology. Distribution and detailed micro-phyiscal properties of atmospheric aerosol. Direct and indirect aerosol radiative forcing and their impact on climate. A second instance of this instrument is in development.Multi-channel/direction/polarisation radiometer
TANSO-CAI
Thermal And Near infrared Sensor for carbon Observation - Cloud and Aerosol Imager
Operational
Detection and correction of cloud and aerosol for TANSO-FTS.Multi-purpose imaging Vis/IR radiometer
TANSO-CAI-2
Thermal And Near infrared Sensor for carbon Observation - Cloud and Aerosol Imager-2
Operational
Detection and correction of cloud and aerosol for TANSO-FTS, aerosol characteristicsMulti-purpose imaging Vis/IR radiometer
VIIRS
Visible/Infrared Imager Radiometer Suite
Operational
Global observations of land, ocean, and atmosphere parameters: cloud/weather imagery, sea-surface temperature, ocean colour, land surface vegetation indices.Multi-purpose imaging Vis/IR radiometer
3MI
Multi-Viewing Multi-Channel Multi-Polarisation Imaging
Being developed
Measure aerosol parameters, air quality index, surface albedo, cloud informationMulti-channel/direction/polarisation radiometer
ACX
GeoXO Atmospheric Composition Instrument
Being developed
 n/a
GXI
GeoXO Imager
Being developed
Detects clouds, cloud properties, water vapour, land and sea surface temperatures, dust, aerosols, volcanic ash, fires, total ozone, snow and ice cover, vegetation index.Multi-purpose imaging Vis/IR radiometer
MAP
Multi-Angular Multi-band Polarimeter
Being developed
Multi-angle polarimeter for supporting the CO2 and CH4 retrieval allowing to accurately estimate the effective light path effects of aerosol. Relatively high spatial resolution and accurate aerosol information will be operationally delivered.Multi-channel/direction/polarisation radiometer
METimage
Multi Spectral Imager
Being developed
Operational multi spectral imager for meteorological EPS-SG VIS/IR Imaging Mission (VII): imagery data for global and regional NWP, NWC, and climate monitoring with information on LST, SST, clouds coverage, height and micro-physics, land surfaces (vegetation, snow/ice, fire), water vapour column, aerosol and atmospheric motion vectors. Provides collocated cloud mask, height & characterisation as well as intra-pixel heterogeneity to other EPS-SG missions (with larger footprint).Multi-purpose imaging Vis/IR radiometer
UVN (Sentinel-4)
UV-visible- near infrared imaging spectrometer (Sentinel-4)
Being developed
Supporting atmospheric composition and air quality monitoring services.High-resolution nadir-scanning SW spectrometer
UVNS (Sentinel-5)
Ultra-violet Visible Near-infrared Shortwave-infrared spectrometer
Being developed
Supporting atmospheric composition and air quality monitoring services. Measurements of atmospheric trace gases, primarily O3, NO2, SO2, HCHO, CH4, CO, CHOCHO as well as Aerosols and UV Index.High-resolution nadir-scanning SW spectrometer
ATLID
ATmospheric LIDar
Approved
Derivation of cloud and aerosol properties - Measurement of molecular and particle backscatter in Rayleigh, co-polar and cross-polar Mie channels.Atmospheric lidar
GHMI
Geostationary HiMawari Imager
Approved
 Multi-purpose imaging Vis/IR radiometer
MAIA
Multi-Angle Imager for Aerosols
Approved
+/-0.05
Pushbroom spectropolarimetric camera on a 2-axis gimbal for multiangle viewing, frequent revisits over targets, and inflight calibration. Major metropolitan areas are sampled with sub-km spatial resolution to study impacts of different types of particulate matter on human health.Multi-channel/direction/polarisation radiometer
Advanced MSU-MR
Advanced Multispectral scanning imager-radiometer
Proposed
Parameters of clouds, snow, ice and land cover, vegetation, surface temperature, fire detection.Multi-purpose imaging Vis/IR radiometer
HiRDLS
High Resolution Dynamics Limb Sounder
No longer operational
Measures atmospheric temperature, concentrations of ozone, water vapour, methane, NOx, N2O, CFCs and other minor species, aerosol concentration, location of polar stratospheric clouds and cloud tops. Currently not collecting data on Aqua.n/a
* Description adapted from WMO.