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.

Air Quality Applied Science Team (AQAST)  – The first generation of HAQAST, from 2011 – 2016, also referred to as HAQAST-1. More information can be found here.

Applied Remote Sensing Training (ARSET) – A NASA program that offers online and in-person training, covering rainings a range of datasets, web portals, and analysis tools and their application to air quality, agriculture, disaster, land, and water resources management. Information on upcoming training may be found 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. Learn more here.

Assimilation – A technique to combine observational data with a numerical model.

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. Learn more here.

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. Learn more here.


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. Learn more here.


Data fusion – a process to integrate multiple data sources, ideally to create more consistent or accurate information than could be gathered from a single source.

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. Learn more here.


​Earth observations – refers to any observations of Earth (in contrast to observations of space).

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). More information can be found here.

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. Learn more here.

Exposure Assessment – Public-health research focused on quantifying the levels of air pollution to which populations are being exposed. More information can be found here.


Geostationary Environment Monitoring Spectrometer (GEMS) – This satellite, launched by the Republic of Korea in 2020, enables monitoring of the Asia-Pacific region. Learn more here.

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

Geographic Information System (GIS) – A type of database with geographic information, combined with tools to manage, analyze, and map the data. Learn more here.

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


Health and Air Quality Applied Sciences Team (HAQAST) – A collaborative team focusing on using NASA satellite data to solve real-world public health and air quality programs. You are currently on the HAQAST website, and you can find more information about the mission of the team and the history on the About page.


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 Imager for Aerosols (MAIA) – A satellite instrument specifically for a mission of studying particulate matter and the relationship to health. Learn more here.

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

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. Learn more here.

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


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. Learn more here.

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. Learn more here.


Ozone Monitoring Instrument (OMI) – An instrument onboard the Aura satellite that measures many atmospheric elements, but primarily ozone. More information can be found here.


Particulate matter (PM) – A mixture of solid particles or liquid droplets in the air, often grouped by size. For example, PM2.5 includes fine particles that are 2.5 micrometers in diameter or less. More information can be found here.


Retrievals – See Level 2 data products.


Satellite – can refer to any object that orbits another object. Typically refers to machines launched into space that move around Earth. More information can be found here.

Satellite-derived PM2.5 – See Aerosol Optical Depth (AOD) above, used to estimate concentrations of particulate matter.

Stakeholder – A group or individual affected by a project, or whoever has a “stake” in the results, key grounps include government, community groups, non-profits, companies and more.


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. Learn more here.

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

Tropospheric Emissions: Monitoring of Pollution (TEMPO) – A spectrometer instrument on a satellite which will monitor air pollution hourly over North America. More information can be found here.

TROPOspheric Monitoring Instrument (TROPOMI) – An instrument on the Copernicus Sentinel-5 Precursor satellite. More information can be found here.

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.​ Learn more here.

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