Glossary of Terms

An ASM is a forum where senior Agency management reviews major acquisitions in programs and projects before authorizing significant budget expenditures. The ASM is held at the Mission Directorate/Mission Support Office level, implementing the decisions that flow out of the earlier Agency acquisition strategy planning. The ASM is typically held early in Formulation, but the timing is determined by the Mission Directorate. The ASM focuses on considerations such as impacting the Agency workforce, maintaining core capabilities and make-or-buy planning, and supporting Center assignments and potential partners.

The aerosol angstrom exponent is an exponent that expresses the spectral dependence of aerosol optical thickness (τ) with the wavelength of incident light (λ). The spectral dependence of aerosol optical thickness can be approximated (depending on size distribution) by, τa = β λα where α is Angstrom exponent (β = aerosol optical thickness at 1 μm).

Angstrom exponent (computed from τ measurements on two different wavelengths) can be used to find τ on another wavelength using the relation.

The Angstrom exponent provides additional information on the particle size (larger the exponent, the smaller the particle size), aerosol phase function and the relative magnitude of aerosol radiances at different wavelengths.

Also known as: back scatter. 

The aerosol back scattering ratio is a measure of scattering in a backward direction ( i.e. towards the incident direction, at a scattering angle of 180°, sometimes also applied to scattering at an angle larger than 90°) for light encountering atmospheric aerosol particles. 

Also known as: aerosol particle size.

Aerosol effective radius is an area weighted mean radius of aerosol particles.

To characterize the size of atmospheric particles, aerosols are usually divided into three modes: the Aitken mode (diameter less than 0.5 μm), the accumulation mode (0.5 to 2.5 μm), and the coarse mode (greater than 2.5 μm). The Aitken and accumulation modes are collectively referred to as fine particles. Human produced emissions (e.g biomass burning in southern Africa and South America and Industrial pollutions) are examples of small mode aerosols. Example of the coarse mode particles are the large Africa's Sahara Desert dust particles that cross Atlantic ocean and reach America

In air pollution studies PM-2.5 aerosols are referred to particulate matter smaller than 2.5 μm that is suspended in the air. In general, submicron aerosols (particles smaller than 1 micron in diameter) affect human health by penetrating to the deepest part of human lungs.

Also known as: extinction coefficient definition.

Aerosol extinction profiles are a measure of attenuation of the light passing through the atmosphere due to the scattering and absorption by aerosol particles. Extinction coefficient is the fractional depletion of radiance per unit path length (also called attenuation especially in reference to radar frequencies). It has units of km-1. The integrated extinction coefficient over a vertical column of unit cross section is called aerosol optical depth or optical thickness.

Also known as: UV aerosol index, aerosol absorbing index, or aerosol absorbing indicator.

The aerosol index is an index that indicates the presence of uv-absorbing aerosols such as dust and soot.

UV aerosol index (AI) is based on a spectral contrast method in a UV region where the ozone absorption is very small. It is the difference between the observations and model calculations of absorbing and non absorbing spectral radiance ratios. 

Also known as: aerosol concentration, aerosol density.

Aerosol mass concentration is a measure of aerosol density.

The columnar aerosol mass concentration (μgm/cm² ) is the total aerosol mass in a vertical column of atmosphere.

Also known as: aerosol optical depth, τ, tau

Aerosol optical thickness is the degree to which aerosols prevent the transmission of light by absorption or scattering of light. The aerosol optical depth or optical thickness (τ) is defined as the integrated extinction coefficient over a vertical column of unit cross section. Extinction coefficient is the fractional depletion of radiance per unit path length (also called attenuation especially in reference to radar frequencies). The optical thickness along the vertical direction is also called normal optical thickness (compared to optical thickness along slant path length).

Aerosol Optical Depth/Thickness Data Pathfinder

Also known as: scattering contribution, Mie contribution, aerosol contribution, atmospheric radiance

Aerosol radiance is the radiance contribution due to aerosol scattering to the observed Earth-atmosphere radiances (as measured by satellite). The satellite viewing a surface (e.g ocean) receives radiance contributions from different sources. These include contribution due to Rayleigh scattering, aerosol scattering (Mie scattering), solar glint, sea foam/whitecap and surface/water leaving radiances. Aerosol radiance contributions depend on wavelength and size distribution of aerosol particles.

Also known as:ω , ωo.

Aerosol single scattering albedo is a measure of the effectiveness of scattering relative to extinction for the light encountering the atmospheric aerosol particles.

In radiative transfer studies, single scattering albedo is the ratio of scattering optical depth to the total optical depth (scattering + extinction) of the atmosphere. It is a dimensionless quantity and ranges from 0 to 1.

 A gaseous suspension of fine solid or liquid particles that can travel vast distances form their original source, affecting air quality and visibility. These particles might serve as nuclei for condensation in the atmosphere. These particles can also absorb and scatter light when sufficiently large, impacting Earth's radiative budget.

 The ratio of radiation reflected by a surface compared to the amount it receives.

Clouds are the chief cause of variations in the Earth's albedo since clouds have highly varying albedo, dependent upon thickness and composition. Old snow is about 55% (0.55), new snow around 80% (0.8). water surfaces vary from very low about 5% (0.05) at high sun elevation to at least 70% (0.70) at low sun angles.

Organic chemical compound derived from the oxidation of primary alcohols, having the common group CHO. Used in manufacturing of dyes, resins, and organic acids.

A formula or set of steps used, sometimes repetitively, to solve a problem. Algorithms implemented as software are delivered to NASA's Science Investigator-led Processing System (SIPS) or to NASA's Science Data Processing Segment (SDPS) by a science investigator (principal investigator, team leader, or Interdisciplinary Investigator) to use as primary tools in the generation of science products. The term includes executable code, source code, job control scripts, and documentation.

An ATBD describes the physical and mathematical description of the algorithms to be used in the generation of data products. It includes a description of variance and uncertainty estimates and considerations of calibration and validation, exception control, and diagnostics. In some cases, internal and external data product flows are required.

Data which are not obtained from the sensor itself (usually provided in the science telemetry) and have the primary purpose to serve the processing of instrument data. This can be divided into data referred to as spacecraft ‘engineering’, ‘core housekeeping’ or ‘subsystem’ data obtained from other parts of the platform and includes parameters such as orbit position and velocity, attitude and its range of change, time, temperatures, pressures, jet firings, water dumps, internally produced magnet fields, and other environmental measurements. Ancillary refers to data that exist purely to serve the data processing; auxiliary data, while helping the process, are also data sets in their own right.

Extensive wind system, of high barometric pressure, that circulates clockwise in the Northern hemisphere and counterclockwise in the Southern hemisphere.

 The farthest point of an elliptical orbit. For an Earth-centered orbit, this is the point where the orbiting body is farthest from the center of the Earth.

A system access point or library function that has a well-defined syntax and is accessible from application programs or user code to provide well-defined functionality. Check out the Earthdata Developer Portal for a list of APIs managed by the ESDS Program.

The archive stores data products, guaranteeing their preservation for future use. This function includes all operations to identify, store and retrieve the data and ensure their integrity.

(ADURD) A document which provides generic requirements for data archiving, data distribution and user services for EOSDIS-supported data.

Also known as: P; Barometric Pressure.

The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the "column" of air directly above the point in question.

The atmospheric pressure decreases as the height above sea level increases. The atmospheric pressure at a station is reported as what it would be if it were actually situated at sea level. Adjustment of atmospheric pressure readings to a common elevation (sea level) removes the influences of the earth's relief (topography) on atmospheric pressure readings. Under normal conditions, the atmospheric pressure above sea level is less that the atmospheric pressure at sea level which is sometimes referred to as one atmosphere.

Also known as: T.

A measure of the average kinetic energy of the air molecules. This is the most measured quantity in the atmosphere.

Also known as: precipitable water vapor, humidity.

Atmospheric Water Vapor, is a measure of the water vapor content of the air.

More than fifty percent of all of the atmospheric water vapor is found below 2 km altitude, and only a minute fraction of the total occurs above the tropopause. Water vapor is a major vehicle for the transport of energy (latent heat) and acts as a regulator of planetary temperatures through absorption and emission of radiation, most significantly in the thermal infrared (the greenhouse effect).

Data that represent spacecraft orientation and onboard pointing information. Attitude data includes: attitude sensor data used to determine the pointing of the spacecraft axes, calibration and alignment data, Euler angles or quaternions, rates and biases, and associated parameters. Attitude generated onboard in quaternion or Euler angle form. Refined and routine production data related to the accuracy or knowledge of the attitude.

An element of metadata, e.g., title, summary, format, dataset language.

Amazon Web Services (AWS) clusters their data centers into separate physical locations, or regions. Users accessing cloud data or services within a region can expect high bandwidth and low latency. Between regions, data are encrypted for security which may increase data latency.

Big data is a broad term for data sets so large or complex that traditional data processing applications are inadequate. Challenges include analysis, capture, data curation, search, sharing, storage, transfer, visualization, querying and information privacy. 

The apparent temperature of the surface assuming a surface emissivity of 1.0. Setting the emissivity to one is equivalent to assuming the target is a blackbody, so the brightness temperature is defined as the temperature a blackbody would be in order to produce the radiance perceived by the sensor.

Brightness temperature is a descriptive measure of radiation in terms of the temperature of a hypothetical blackbody emitting an identical amount of radiation at the same wavelength. The brightness temperature is obtained by applying the inverse of the Planck function to the measured radiation. Depending on the nature of the source of radiation and any subsequent absorption, the brightness temperature may be independent of, or highly dependent on, the wavelength of the radiation.

Bromine monoxide (BrO) plays an important role in the chemistry of the atmosphere because of its very high efficiency as a catalyst of the ozone destruction.

BrO enters the atmosphere as a result of both natural and anthropogenic activities. In the atmosphere BrO is produced from the destruction of methyl bromide (both natural and anthropogenic in origin). The chemical reaction involving BrO and chlorine dioxide (OClO) result in the depletion of ozone in the stratosphere.

1. Subsets of data set other than the directory and metadata that facilitates user selection of specific data having the required characteristics. For example, for image data, browse data could be a single channel of multi-channel data, and with degraded resolution. The form of browse data is generally unique for each type of data set and depends on the nature of the data and the criteria used for data selection within the related science discipline.

2. Data produced primarily to provide other investigators with an understanding of the type and quality of data available. Typically, browse data sets are limited in size or resolution. The specific form of browse data depends on the type of instrument or discipline with which the browse data is related. Browse data is sometimes considered to be a sample of available data.

3. Browse data facilitates access to real-time or priority playback data which receive minimal processing and are forwarded to the user for his review/use. The user may provide additional processing to suit his requirements.

Visual representation of a product (as an image) to help and support product selection in the frame of the user service facility. Synonyms are: Browse, Quick-look, and Preview.

The process of quantitatively defining the system responses to known, controlled signal inputs.

The collection of data required to perform calibration of the instrument science data, instrument engineering data, and the spacecraft or platform engineering data. It includes pre-flight and in-flight calibration measurements, calibration equation coefficients derived from calibration software routines, and ground truth data that is to be used in the data calibration processing routine.

An observational study used to acquire targeted observations or samples to support a clearly defined science or research objectives. Also called (or at least related to) what some stakeholders call a Mission, Project, Field Campaign, or Field Investigation. A campaign may be a multi-year program with multiple projects, such as the Arctic-Boreal Vulnerability Experiment (ABoVE), an Earth Ventures Suborbital (EVS) mission, such as Delta-X, or a single project targeting a specific set of measurements, such as the CARbon Atmospheric Flux Experiment (CARAFE).

Halocarbon compound used in air conditioning systems as a refrigerant. One of two primary chlorofluorocarbons that photolyze at high altitudes to release chlorine atoms. An important factor in ozone depletion. Also known as dichlorofluoromethane.

Chapman Reactions: stratospheric reactions in which ozone dissociates into molecular oxygen and atomic oxygen, and the resulting free oxygen atoms recombine with ozone to form molecular oxygen. The process was first described by a British physicist named Sydney Chapman in 1930.

A set of metadata conventions that were invented for climate and weather forecast data but have since been applied to describe other kinds of Earth Science data, with the intention of promoting the processing and sharing of data.

 A visible aggregate of minute water droplets and/or ice crystals in the atmosphere above the Earth's surface.

The Common Metadata Repository-SpatioTemporal Asset Catalog (CMR-STAC) is NASA's implementation of the STAC specification for all NASA holdings within Earth Observing System Data and Information System (EOSDIS). STAC allows spatiotemporal assets to be easily searched/discovered and accessed. Spatiotemporal assets are any files that represent information about Earth for a certain space and time. A query to CMR-STAC will be translated to a CMR query before being translated into STAC collections.

See Data Set Series

These are metadata elements that describe an entire set of data products or files. Values of collection metadata apply to all of the products in a specific collection. Collections may represent the same release of any given data product, sets of data generated during an experiment, a campaign or an algorithmic test.

A means for enhancing the addressing and access of elements contained in a digital object in the cloud.

The transfer of heat through motion within a liquid, solid or gas (e.g. the atmosphere).

 A two dimensional graphical representation of the geographic coverage of selected inventory granules.

CDRs evaluate the integrity of the program integrated design, including its projects and ground systems. CDRs also help meet mission requirements with appropriate margins and acceptable risk within cost and schedule constraints. CDRs also determine if the integrated design is appropriately mature to continue with the final design and fabrication phase.

CERRs evaluate the readiness of the program and its projects to execute a critical event during the flight operations phase of the life cycle.

Scientific or technical measurements, values calculated therefrom, observations, or facts that can be represented by numbers, tables, graphs, models, text, or symbols which are used as a basis for reasoning and further calculation.

For NASA's Earth Science Program and according to NASA's Earth Science Data & Information Policy, the term 'data' includes observation data, metadata, products, information, algorithms, including scientific source code, documentation, models, images, and research results.

Data assimilation is defined as the process of combining observations with model simulations to enhance the accuracy of predictions.

A major release of a data product, or of a set of closely related data products, which can be followed by minor releases within the same collection.

See also: Data Set Series on this page.

An entity responsible for archiving and distributing data products. 

See also: DAAC.