LP DAAC Dictionary

Unsure what a term means? Check out the LP DAAC Dictionary to learn what various terms mean in the LP DAAC world.


Aerosol Optical Depth

Aerosol optical depth is a measure of the extinction of the solar beam by dust and haze. In other words, particles in the atmosphere (dust, smoke, pollution) can block sunlight by absorbing or scattering light. AOD tells us how much direct sunlight is prevented from reaching the ground by these aerosol particles. It is a dimensionless number that is related to the amount of aerosol in the vertical column of atmosphere over the observation location.


Describes the ratio of radiant energy scattered upward and away from the surface in all directions to the downwelling irradiance incident upon that surface.

Application Program interface (API)

According to Wikipedia, "In computer programming, an application programming interface (API) is a set of routines, protocols, and tools for building software and applications. An API expresses a software component in terms of its operations, inputs, outputs, and underlying types, defining functionalities that are independent of their respective implementations, which allows definitions and implementations to vary without compromising the interface. A good API makes it easier to develop a program by providing all the building blocks, which are then put together by the programmer. An API may be for a web-based system, operating system, or database system, and it provides facilities to develop applications for that system using a given programming language." As examples in EOSDIS, NASA's Common Metadata Repository (CMR) and Global Imagery Services (GIBS) provide an APIs to support client developers.

Application for Extracting and Exploring Analysis Ready Samples (AppEEARS)

An online data access application that offers a straightforward and efficient way to rapidly access and transform geospatial data from a variety of federal data archives. AρρEEARS enables users to subset geospatial datasets spatially, temporally, and by band/layer, reducing the volume of data downloaded by the end user. Two types of sample requests are available: point samples at specific geographic coordinates, and area samples for spatial regions of interest via vector polygons. Sample requests submitted to AρρEEARS provide users with the desired analysis ready data values and decoded quality data values. Interactive visualizations with summary statistics are provided for each sample within the application. More information on AppEEARS can be found on the AppEEARS website: https://lpdaacsvc.cr.usgs.gov/appeears/ and throughout the LP DAAC website.


A NASA Earth-observing satellite that was launched on May 4, 2002 and has one of the MODIS sensors aboard. More information on Aqua can be found on the Aqua website:https://aqua.nasa.gov/ and throughout the LP DAAC website.

Algorithm Specification Document (ASD)

Created by the principal investigators of a data product to describe the algorithm used in the generation of the data.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)

One of the five sensor systems aboard the Terra satellite. ASTER is a partnership between NASA, Japan's Ministry of Economy, Trade and Industry (METI), the National Institute of Advanced Industrial Science and Technology (AIST) in Japan, and Japan Space Systems. More information on Terra ASTER can be found on the ASTER website: https://asterweb.jpl.nasa.gov/ and throughout the LP DAAC website.

Algorithm Theoretical Basis Document (ATBD)

Developed for NASA's Earth Observing Systems (EOS) instrument products, although some ATBDs address more than one product, and some products are addressed by more than one ATBD. ATBDs typically provide the theoretical basis, both the physical theory and the mathematical procedures and possible assumptions being applied, for the calculations that are made to convert the radiances received by the instruments to geophysical quantities. The geophysical quantities are then available to the scientific community for studies of the various characteristics of the Earth system.



In radiometry, a relatively narrow region of the electromagnetic spectrum to which a remote sensor responds; a multispectral sensor makes measurements in a number of spectral bands.

Bidirectional Reflectance Distribution Function (BRDF)

Specifies the behavior of surface scattering as a function of illumination and view angles at a particular wavelength.

Black-Sky Albedo (BSA)

Albedo in the absence of a diffuse component and is a function of solar zenith angle.


Climate Modeling Grid (CMG)

These datasets provide global coverage of land products in a Geographic coordinate reference system with a spatial resolution of 0.05 degrees. The objective is to provide products at consistent low resolution spatial and temporal scales suitable for global modeling.


Datasets sharing the same product specification. They are named dataset series as they may be mapped to ‘dataset series’ according to the terminology defined in ISO 19113, ISO 19114 and ISO 19115.

Collection Metadata

Elements that describe a collection of data products. Values of collection metadata apply to all of the data in that collection. Typical metadata in this category describes information about the data products, including the platform, sensor, documentation, URLs for distribution, publication, and DOI landing pages, collection data dates, processing level, and more.

Combined Moderate Resolution Imaging Spectroradiometer (MODIS)

Data products generated with both Terra and Aqua MODIS inputs are referred to as a combined (MCD) product.


An image created from multiple input images, either spatially (mosaic) or temporally (8-day composite image).



A product that is no longer publicly available/supported by the LP DAAC.

Digital Elevation Model (DEM)

A raster representing the elevation of the surface of the land.

Digital Object Identifier (DOI) Landing Page

These are web pages for each individual data product distributed by the LP DAAC. Included in these pages are information about the product, how to cite the product, related product documentation, how to access the data, and more. DOI links are persistent and will remain the same, even if the underlying URL changes.


Earth Surface Mineral Dust Source Investigation (EMIT)

The Earth Surface Mineral Dust Source Investigation (EMIT) is an Earth Ventures-Instrument (EVI-4) Mission to map the surface mineralogy of arid dust source regions via imaging spectroscopy in the visible and short-wave infrared (VSWIR). More information on EMIT can be found here: https://earth.jpl.nasa.gov/emit/.

Earth Observing System Data Information System (EOSDIS)

A key core capability in NASA’s Earth Science Data Systems Program. It provides end-to-end capabilities for managing NASA’s Earth science data from various sources – satellites, aircraft, field measurements, and various other programs. For the EOS satellite missions, EOSDIS provides capabilities for command and control, scheduling, data capture and initial (Level 0) processing. These capabilities, constituting the EOSDIS Mission Operations, are managed by NASA's Earth Science Mission Operations (ESMO) Project. NASA network capabilities transport the data to the science operations facilities. The remaining capabilities of EOSDIS constitute the EOSDIS Science Operations, which are managed by NASA's Earth Science Data and Information System (ESDIS) Project. These capabilities include: generation of higher level (Level 1-4) science data products for EOS missions; archiving and distribution of data products from EOS and other satellite missions, as well as aircraft and field measurement campaigns. EOSDIS science operations are performed within a distributed system of many interconnected nodes (Science Investigator-led Processing Systems, or SIPS; and Distributed Active Archive Centers, or DAACs) with specific responsibilities for production, archiving, and distribution of Earth science data products. The DAACs serve a large and diverse user community (as indicated by EOSDIS performance metrics) by providing capabilities to search and access science data products and specialized services.

ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS)

Attached to the International Space Station, ECOSTRESS measures the Earth's surface temperature to better understand how much water is used by plants. More information on ECOSTRESS can be found on the ECOSTRESS website: https://ecostress.jpl.nasa.gov/ and throughout the LP DAAC website.


The height above or below a fixed reference point in a geographic location.


Emissivity is the measure of an object's ability to emit infrared energy. Emissivity is a unitless quantity, and the emissivity of most natural Earth surfaces ranges between approximately 0.6 and 1.0, but surfaces with emissivities less than 0.85 are typically restricted to deserts and semi-arid areas.

Evaporative Stress Index (ESI)

A value computed from clear-sky estimates of the relative daily evapotranspiration (ET) fraction: ESI = ET/ETo. ET is ETdaily from the ECOSTRESS Level 3 product and ETo is the reference ET.

Evapotranspiration (ET)

The process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants.

Enhanced Vegetation Index (EVI)

A vegetation indices product that tells about the health of the vegetation in the area. It has improved sensitivity over high biomass regions by separating the canopy background signal, and reducing the atmospheric influences.

Enhanced Vegetation Index (EVI) 2

A reformation of the standard 3-band EVI, using the red band and NIR band. EVI 2 is used as a "backup algorithm" for cases when the blue band yields problematic VI values, mainly over dense snow or pixels with extensive sub pixel clouds.


File Specification

Provides a description of the product file including Scientific Data Sets and their attributes.

Fractional Photosynthetically Active Radiation (FPAR)

The fraction of incident photosynthetically active radiation, 400-700 nanometers (nm), absorbed by the green elements of a vegetation canopy.

Full Waveform

The observable measured by the GEDI (Global Ecosystem Dynamics Investigation) Lidar system, which contains the recorded voltage (returned light energy) captured by the laser pulse.


Global Ecosystem Dynamics Investigation (GEDI)

Attached to the International Space Station, GEDI observes nearly all tropical and temperate forests using a self-contained laser altimeter and makes precise measurements of forest canopy height, canopy vertical structure, and surface elevation. More information on GEDI can be found on the GEDI website: https://gedi.umd.edu/ and throughout the LP DAAC website.

Global Hyperspectral Imaging Spectral-library of Agricultural crops (GHISA)

GHISA is a hyperspectral library of all major agricultural crops of the world. More information on GHISA can be found on the GHISA website and on the LP DAAC website. 


The smallest aggregation of data which is independently managed.

Granule Metadata

Elements that describe a single granule of a data product. Values of granule metadata apply to all of the data in that one granule. Typical metadata in this category describe spatial and temporal extent of the data as well as the quality and lineage of the data.

Gross Primary Productivity (GPP)

The initial daily total of photosynthesis.


Harmonized Landsat and Sentinel-2 (HLS)

The Harmonized Landsat and Sentinel-2 (HLS) project is a NASA initiative to produce seamless, harmonized surface reflectance data from the Operational Land Imager (OLI) and Multi-Spectral Instrument (MSI) aboard Landsat 8 and Sentinel-2 Earth-observing satellites, respectively. For more information on HLS please visit: https://hls.gsfc.nasa.gov/.


Imaging of an object wherein a large number of small, continuous spectral bands are collected.


Infrared (IR)

The region of the electromagnetic spectrum defined by wavelengths between 6,700 and 7,000 nanometers (nm).


Joint Polar Satellite System (JPSS-1) (NOAA-20)

Joint Polar Satellite System (JPSS-1) (NOAA-20) is the second spacecraft within NOAA's and NASA’s partnership of next generation polar-orbiting satellites. One of the VIIRS satellite sensors is aboard the JPSS-1 (NOAA-20) satellite. For more information on JPSS-1 please visit https://www.jpss.noaa.gov/mission_and_instruments.html.



Land Cover

The vegetation (natural or planted) or man-made constructions (buildings, etc.) which occur on the earth surface. Water, ice, bare rock, sand and similar surfaces also count as land cover.

Land Surface Temperature (LST)

Specifically refers to the temperature of the land's surface not the surrounding air temperature. LST data products distributed by the LP DAAC are available in Kelvin.

Land Use

A series of operations on land, carried out by humans, with the intention to obtain products and/or benefits through using land resources.

Leaf Area Index (LAI)

The one-sided green leaf area per unit ground area in broadleaf canopies and the one-half the total needle surface area per unit ground area in coniferous canopies.

Level 2 data

Derived geophysical parameters (e.g. sea surface temperature, leaf area index) at the same resolution and location as Level 1 source data.

Level 2-G data

Derived geophysical parameters mapped on uniform space-time grid scales.

Level 3 data

Data or retrieved geophysical parameters which are spatially and/or temporally re-sampled (i.e. derived from Level 1 or 2 products), usually with some completeness and consistency. Resampling may include averaging and compositing.

Level 4 data

Model output or results from analyses of lower level data (i.e., variables that are not directly measured by the instruments, but are derived from these measurements; could be derived from multiple instrument measurements).

Light Detection and Ranging (LIDAR)

A remote sensing method that uses light as a pulsed laser to measure distance to the Earth and allows for topographical modeling of the Earth's surface.


Making Earth System Data Records for Use in Research Environments (MEaSUREs)

A NASA program that expands our understanding of the Earth systems using consistent records.

Midwave Infrared (MIR)

The region of the electromagnetic spectrum defined by wavelengths between 3,000 and 5,000 nanometers (nm).

Moderate Resolution Imaging Spectroradiometer (MODIS)

An instrument is operating on both the Terra and Aqua spacecraft. It views the entire surface of the Earth every one to two days. MODIS data contribute to a range of land and water application areas including wildfire monitoring, temperature and emissivity changes, land surface change, vegetation and ecosystem dynamics, natural disasters, and agriculture studies. More information on MODIS can be found on the MODIS website: https://modis.gsfc.nasa.gov/ and throughout the LP DAAC website.



A point on Earth directly beneath a satellite.

Near infrared (NIR)

The region of the electromagnetic spectrum defined by wavelengths between 700 and 1,100 nanometers (nm).

Net Primary Productivity (NPP)

The fraction of biomass produced after accounting for energy lost due to cellular respiration and maintenance of plant tissue.

Normalized Difference Vegetation Index (NDVI)

Quantifies plant “greenness” or photosynthetic activity by measuring the difference between near-infrared (which vegetation strongly reflects) and red light (which vegetation absorbs).



The path described by a space-borne body in its periodic revolution. Earth satellite orbits with inclinations near 0 degrees are called equatorial orbits because the satellite stays nearly over the equator. Orbits with inclinations near 90 degrees are called polar orbits because the satellite crosses over (or nearly over) the north and south poles.


Photosynthetically Active Radiation (PAR)

A light of wavelengths 400-700 nm and is the portion of the light spectrum utilized by plants for photosynthesis.

Product long name

The official name of a data product, which essentially tells you the bare bones information about the product. (ex: MODIS/Terra Vegetation Indices 16-Day L3 Global 250 m SIN Grid V006. This tells you the product is from the Terra MODIS satellite sensor, is a vegetation indices product, is a 16-Day composite, is a level 3 product, is provided across the globe at 250 meter spatial resolution, from the MODIS Sinusoidal Grid, and is a Version 6 product).

Product short name

A simple code for a product. It begins with a set of letters that indicate which sensor/project the data comes from, a set of numbers that typically are the same for all products in that product suite, and then a set of numbers and letters to indicate the specific product. (ex: MOD13Q1. This tells us the product is from Terra MODIS (MOD), a vegetation indices product (13)).

Product Specification Document (PSD)

Created by the principal investigators of a data product to describe the format and contents of the dataset.

Product Version

Describes which version of a data product that product is, occasionally data are reprocessed into a newer version that contains updated information including algorithms, inputs, lookup tables and more.




Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object.


Science Dataset (SDS)

A layer or variable contained within a hierarchical data format (HDF) containing scientific information/data.

Shuttle Radar Topography Mission (SRTM)

A collaborative effort by NASA, the National Geospatial-Intelligence Agency (NGA), and the participation of German and Italian space agencies. This collaboration aimed to generate a near-global digital elevation model (DEM) of Earth using radar interferometry. SRTM was the primary (and virtually only) payload on the STS-99 mission of the space shuttle Endeavour, which launched February 11, 2000, and flew for 11 days.

Spatial Extent

Indicates where the data can be found on the Earth.

Spatial Resolution

Describes how many meters are in a single pixel in the data.

Suomi National Polar-orbiting Partnership (S-NPP)

Suomi National Polar-orbiting Partnership (S-NPP) is the satellite that carries one of the Visible Infrared Imaging Radiometer Suite (VIIRS) satellite sensors. For more information on S-NPP VIIRS data please visit: https://viirsland.gsfc.nasa.gov/.

Surface Radiance

The amount of light a satellite instrument observes from an object.

Surface Reflectance

The amount of light reflected by the surface of the earth; it is a ratio of surface radiance to surface irradiance, and as such is unitless, and typically has values between 0.0 and 1.0.


The area covered by a scan of a spaceborne instrument as it orbits the Earth.

Shortwave Infrared (SWIR)

The region of the electromagnetic spectrum defined by wavelengths between 1,000 and 3,000 nanometers (nm).


Temporal Resolution / Extent

The period of time captured within a data granule.


A NASA Earth-observing satellite that was launched on December 18, 1999 and has one of the MODIS sensors and the ASTER sensor aboard. More information on Terra can be found here: https://terra.nasa.gov/.

Thermal Anomalies

Sources of heat on the Earth that are not fires, for example volcanoes.

Thermal Infrared (TIR)

The region of the electromagnetic spectrum defined by wavelengths between 8,000 and 15,000 nanometers (nm).



These data contain reconstructed original data values. Radiometric calibration coefficients, geometric correction coefficients and other auxiliary data have been calculated and appended to the metadata but have not been applied to the data.

User Guide

A document containing the necessary technical information for users to interpret and use the data products.


Vegetation Continuous Fields (VCF)

Maps of annual global fractional vegetation cover.

Vegetation Indices (VI)

An algorithm to quantify the concentrations of green leaf vegetation within an areal unit. Remote sensing phenology studies use this data gathered by satellite sensors that measure wavelengths of light absorbed and reflected by green plants.

Visible Infrared Imaging Radiometer Suite (VIIRS)

An instrument operating on the Suomi National Polar-orbiting Partnership (S-NPP). It views the entire surface of the Earth twice a day, once during the day and once at night. VIIRS data contribute to a range of land and water application areas including wildfire monitoring temperature and emissivity changes, land surface change, vegetation and ecosystem dynamics, natural disasters, and agriculture studies. VIIRS products aim to extend the data life cycle of MODIS products. VIIRS is a joint mission between NASA and NOAA, VIIRS data distributed by the LP DAAC are NASA produced data products. More information on VIIRS can be found on the VIIRS website:https://viirsland.gsfc.nasa.gov/ and through out the LP DAAC website.

Visible and Near-Infrared (VNIR)

A portion of the electromagnetic spectrum that has wavelengths between approximately 400 and 1400 nanometers (nm). It combines the full visible spectrum with an adjacent portion of the infrared spectrum up to the water absorption band between 1400 and 1500 nm.



A record of the distribution of returned light energy captured by a Lidar laser system.

White-Sky Albedo (WSA)

Albedo in the absence of a direct component when the diffuse component is isotropic.