We’ve gathered here some of the most common terms that you’ll run across when working with satellite data. This glossary is based upon a much more comprehensive one originally developed for AQAST, which can be found here. 


Atmospheric Infrared Sounder (AIRS) – A satellite aboard the Aqua spacecraft that supports climate research and improves weather forecasting. It is the most advanced atmospheric sounding system developed for space to date. More information may be found here.

Aerosol Optical Depth (AOD) – A numerical measurement of the transparency of aerosols, most commonly in visible wavelengths. A small number (less than 0.1) indicates a clear sky, whereas an AOD of 1 or greater is hazy. AOD is measured by satellites like MODIS. More information here.

Aqua –Aqua is a NASA satellite housing instruments that measure aerosols and vegetation, as well as air, land, and water temperatures. Its primary focus, though, is data collection of the earth’s water cycle (hence its name) including oceanic evaporation, soil moisture, clouds, precipitation, snow cover, and sea/land ice.

Atmospheric Model version 3 (AM-3) – A chemistry-climate model developed at NOAA’s Geophysical Fluid Dynamics Laboratory that is the atmospheric component of the CH3 global climate model.

Aura – The Aura satellite houses instruments that collect data from space to monitor the many natural processes that affect the Earth, such as ozone, air quality, and climate.


Background ozone – The level of ozone in an area if human activity were not present.


Criteria Pollutants – Six substances controlled by the EPA’s NAAQS standards. They include carbon monoxide, lead, particle pollution, ozone, nitrogen dioxide and sulfur dioxide.


DISCOVER AQ – A NASA project designed to distinguish between pollution in the upper levels of the atmosphere and pollution closest to Earth’s surface in the air that humans breathe.


Earth Observing System (EOS) – EOS is a coordinated series of satellites designed by NASA to observe the globe and its processes over a long period of time. It helps scientists better understand the interactions between the Earth and its surface, ecosystems, atmosphere and oceans. Read more here.

Emission Inventory – An estimate of emissions for a single chemical or multiple chemicals from a single emission sector (such as electricity), or from multiple emissions sectors, for some particular region of the Earth (e.g. a state, country, the entire globe).

Episode/Air quality Event – An air quality event occurs when ambient air quality is affected more than usual, often by high winds, volcanic eruptions, large fires, seismic activity, or even fireworks.

Exceedance – When levels of a pollutant (such as surface ozone) increases in a certain area to the point that levels exceed national standards.

Exceptional Event – An exceptional event is any unusual or naturally occurring event that can affect air quality but which is not able to be reasonably controlled using techniques that tribal, state, or local air agencies may implement in order to attain and maintain the National Ambient Air Quality Standards.

Exposure Assessment – Public-health research focused on quantifying the levels of air pollution to which populations are being exposed.


Geostationary Operational Environmental Satellite (GOES) – A satellite that observes information regarding weather forecasting, severe storm tracking, and meteorology research.

Ground-based data – Data that comes from monitors or other instruments based on Earth.


Level 1 data products – Raw satellite irradiance data (how much a satellite can detect of certain properties at different wavelengths).

Level 2 data products – Swath-level (satellite’s eye level) data on derived variables based on Level 1 data. Level 2 data products are more usable for air quality managers, and are often called “retrievals” because they depend on the interpretation of Level 1 products.

Level 3 data products – A global, gridded version of Level 2 data.


Multi-angle Imaging Spectroradiometer (MISR) – A sensor onboard the Terra satellite that measures Earth processes.

Moderate Resolution Imaging Spectroradiometer (MODIS) – An instrument onboard the Terra and Aqua satellites that measures many elements; primarily used in the HAQAST community for its ability to measure Aerosol Optical Depth.

Measurements of Pollution in the Troposphere (MOPITT) – A sensor onboard the Terra satellite that measures Earth processes.


National Ambient Air Quality Standards (NAAQS) – Standards set by the EPA under the Clean Air Act to regulate certain pollutants that are considered threatening to public health. The six “criteria pollutants” under the NAAQS are carbon monoxide, lead, particle pollution, ozone, nitrogen dioxide, and sulfur dioxide.

Network Common Data Format (netCDF) – A way of digitally organizing atmospheric data (or other types of data). It allows for the binary storage of very large datasets, so that information on variables and the time and space that those variables represent may be quickly stored in a clear, organized, accessible way.


Ozone Monitoring Instrument (OMI) – An instrument onboard the Aura satellite that measures many atmospheric elements, but primarily ozone.


Retrievals – See Level 2 data products.


Terra – The flagship satellite in NASA’s Earth Observing System. Terra has five sensors onboard (ASTER, CERES, MISR, MODIS and MOPITT) that study the interactions between land, oceans, and the sun.

Tropospheric Emission Spectrometer (TES) – Pronounced “Tees,” TES is an instrument that measures many components of the troposphere like carbon monoxide, carbon dioxide, and ozone. TES is aboard the Aura satellite.

True color image – A composite of images taken of the Earth from space that show true-to-life coloring, rather than one changed to represent some set of information, such as temperature or the presence of chemicals.​

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