Glossary of Terms

The FA is prepared by the project to establish the technical and acquisition work that needs to be conducted during formulation and defines the schedule and funding requirements during Phase A and Phase B for that work.

The FAD is issued by the Mission Directorate Associate Administrator (MDAA) to authorize the formulation of a program whose goals will fulfill part of the Agency's Strategic Plan and Mission Directorate strategies and establish the expectations and constraints for activity in the Formulation Phase. In addition, a FAD or equivalent is used to authorize the formulation of a project. (See Appendix E.)

A term used in data processing when the data is moving from one version to another version.

Spectrometer that consists of a collimator and beamsplitter, which divides the source beam into two parallel beams with equal amplitudes. By scanning the movable mirror over some distance, an interference pattern is produced that encodes the spectrum of the source.In its simplest form, a Fourier transform spectrometer consists of two mirrors located at a right angle to each other and oriented perpendicularly, with a beamsplitter placed at the vertex of the right angle and oriented at a 45° angle relative to the two mirrors.

Geopotential is the potential energy acquired by unit mass on being raised through unit distance in a field of gravitational force of unit strength. The geopotential meter is related to the dynamic meter by the expression one geopotential meter = 0.98 dynamic meter. It is roughly the height of a pressure surface in the atmosphere above mean sea level.

The equation which defines the relationship between geopotential height (Z) and geometric height (z) is Z = gz/980. Thus when gravity (g) has its near average value of 980 cm/sec², heights in geopotential meters and and geometric meters are the same; for g < 980 cm/sec² the height in geopotential meters is smaller, for g > 980 cm/sec² it is bigger.

Geopotential (from the dynamic point of view) is a better measure of height in the atmosphere than is geometric height since energy is in general lost or gained when air moves along a geometrically level surface but not when it moves along an equigeopotential surface.

 A satellite that remains over a fixed point because its rate of travel corresponds to the Earth's rate of rotation. Geostationary satellites follow a circular orbit at a fixed distance from the orbit's barycenter. 

The goal of the Global Land Data Assimilation System (GLDAS) is to ingest satellite- and ground-based observational data products, using advanced land surface modeling and data assimilation techniques, in order to generate optimal fields of land surface states and fluxes.

An attribute that applies to either the entire file or the entire collection of files.

GIBS provides full resolution visual representations of NASA Earth science data in a free, open, and interoperable manner.

1. The smallest aggregation of data which is independently managed (i. e. described, inventoried, retrievable). Granules may be managed as logical granules and/or physical granules. 
   
   See also: Scene 
    
2. The smallest aggregation of independently managed (i.e., described, inventoried, retrievable) data at a DAAC. Some web applications and services provided by DAACs allow for the subsetting of granules. One granule usually comprises one file, more rarely multiple files. The latter is not optimal as it complicates data management by both the archive and users, and utilization by tools and services.

These are 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. 

See also: Granule.

Surface with parallel grooves or slits that enable diffraction of incoming light into optical spectra.

Greenhouse gases are those gases in the atmosphere that both emit and absorb radiation in the long-wavelength infra-red region of the electromagnetic spectrum. The absorption and subsequent downward re-emission of the Earth's thermal radiation by greenhouse gases is the primary cause of the greenhouse effect. The greenhouse effect alters the radiative balance of the Earth resulting in a higher surface temperature than would exist absent any atmosphere. 

The most abundant greenhouse gases in the atmosphere are water vapor (H₂O), carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), ozone (O₃), and chlorocluorocarbons (CFC).

The Goddard Satellite-based Surface Turbulent Fluxes (GSSTF) have been widely used by scientific communities for global energy and water cycle research and regional and short period data analysis since its official release in 2000/2001. Accurate sea surface fluxes measurements are crucial to understanding the global water and energy cycles.

The fluxes are derived using the Special Sensor Microwave Imager (SSM/I) surface winds and surface air humidity, as well as the 2 m air and sea surface temperatures of the National Center for Environmental Prediction (NCEP-NCAR) reanalysis, by means of a bulk aerodynamic algorithm based on the surface layer similarity theory.

Harmony is the name of the collective NASA EOSDIS effort to make data access consistent and easy across the different NASA Distributed Active Archive Centers (DAACs). As the individual DAACs migrate data to the cloud, Harmony allows users to seamlessly access and analyze data from multiple DAACs directly within the cloud (analysis-in-place). 

Harmony also allows users to subset and download data directly to their local work environment. Harmony is created through the merger of existing on-premises services from the individual DAACs into an overarching cloud service.

The Hierarchical Data Format (HDF) is designed to facilitate managing and sharing scientific data. HDF includes two formats (HDF4 and HDF5), software for accessing data in HDF formats, and applications for working with HDF data. 

HDF is designed for efficient storage and access of high volume, complex data, and for mixing varieties of data types in a single container.

 A general term referring to water vapor in the air.

Infrared radiance is the intensity of infrared radiation. In radiometery, radiance refers to measure of the intrinsic radiant intensity emitted by a radiator in a given direction. Radiance is measured in watts per square meter and steradian.

Infrared radiation refers to that portion of the electromagnetic spectrum lying between visible light and microwaves. The wavelength range is approximately between 720 and 1 mm. In meteorology, this range is often further divided into the solar infrared and terrestrial radiation, with the division occurring around 4 m. 

Dominant absorbers of infrared radiation include the Earth's surface, clouds, water vapor, and carbon dioxide. By Kirchhoff's law, these are also good emitters of infrared radiation. 

Radiance is a radiometric term for the rate at which radiant energy in a set of directions confined to a unit solid angle around a particular direction is transferred across unit area of a surface (real or imaginary) projected onto this direction.

Sensor that measures the intensity of infrared radiation (720 nm-1500 nm) within a specific field of view.

The ingestion function accepts data from different sources: ground segment reception, processing or data migration elements. The received data is quality checked and metadata including browse images are obtained from the data. The data and metadata form a data product. The product is consistently submitted to archiving and cataloguing.

The solid angle through which a pixel sensor is sensitive to electromagnetic radiation at any one time. This is the measure of the spatial resolution of the remote sensing system. The area of the ground, or other target area, viewed by a sensor at a given point in time.

The instrument calibration function is the determination of parameters describing instrument characteristics. They are to be used by the instruments and ground processing to generate calibrated and comparable physical values. These parameters vary for different instruments and modes. And they may vary over time in the long run (degradation).

IPAs are agreements between ESDIS and projects not managed by ESDIS. Generally, the projects involved agree on an exchange of support services and data. From the interface control viewpoint, these agreements identify the need for an interface and the scope of the interface.

ICDs are used to record design agreements for the interfaces between participating organizations. ICDs provide a means to evaluate and control all mutually interdependent and/or interacting design parameters of the interface.

IRDs define the requirements for data exchanges across an interface between separately managed systems or subsystems. The requirements statements in IRDs are derived directly from project requirements documents.

The ability of different information technology systems and software applications to communicate, exchange data, and use the information that has been exchanged. 

In Earth observation it includes e.g. interoperable discovery and access, i.e. the capability of the user interface and administrative software of one instance of a catalogue service to interact with other instances of catalogue services. E.g. the capability of accessing granules in one data format with APIs or services of another API.

The inventory function provides organization capabilities for archiving management. Data products can be grouped, searched and identified for retrieval, statistics and reorganization. Inventory is also referred to the list of available items stored and/or controlled in a storage warehouse system. 

In this latter case it is necessary to specify the kind of inventory, e.g. ICT Inventory for infrastructure inventory list.

 Flux divided by the area through which it passes, designated as watt per square meter (W/m²).

A key decision point (KDP) is the event at which the Decision Authority determines the readiness of a program/project to progress to the next phase of the life cycle (or to the next KDP).

LRRs evaluate a program/project and its ground, hardware, and software systems for readiness for launch.

LVs are rockets that send people and other payloads into space.

Rigid, outermost mass of Earth composed of rock, soil, and sediment. Below the lithosphere is the area called the asthenosphere, which is a hotter, and deeper part of the upper mantle and is able to convect. The lithosphere reacts to stress elastically and through brittle failure; the asthenosphere reacts viscously and via plastic deformation.

The act of maintaining information in a correct and independently understandable form over the long term, i.e. a period of time long enough to be concerned with the impact which changing technologies, including support for media and data formats, and changing user communities will have on the information being held in a repository. 

See: Preservation.

The top of the mesosphere and the base of the thermosphere. The mesopause is usually located at heights of 85-95 km, and is the site of the coldest temperatures in the atmosphere. Temperatures as low as 100 K (- 173° C) have been measured at the mesopause by rockets.

Region of the atmosphere, between the stratosphere and the mesopause, from approximately 50 km to 85-100 km, in which temperature decreases with altitude.

Data about data, contained in data sets, and which provides an understanding of the content and utility of the data set. Metadata may be used to select on data for a particular scientific investigation. 

Metadata is intended as information describing significant aspects of a resource (Earth Observation space data in this context). They are created for the purposes of data search, discovery and access management and may exist at various levels, typically from data collection through to the individual variables of each data file in a collection.

Also known as: marsh gas,

Methane (CH₄) a colorless and inflammable gas, is most abundant in the troposphere.

Methane is a strong greenhouse gas and an important source of stratospheric water vapor that contributes to global warming. The concentration of methane has doubled since pre-industrial times. The atmospheric mixing ratio of methane is currently about 1.7 parts per million. This increase is attributed to intensified human activity in agriculture, biomass burning, and fossil fuel consumption. 

The atmospheric lifetime of methane is about eight years. It reacts with atmospheric hydroxyl (OH) in the troposphere forming formaldehyde (HCHO), carbon monoxide (CO) and ozone (O₃).

Microwave radiance is the intensity of microwave radiation. In radiometery, radiance refers to a measure of the intrinsic radiant intensity emitted by a radiator in a given direction. Radiance is measured in watts per square meter and steradian.

Microwave radiation refers to electromagnetic radiation generally in the frequency range between 300 MHz and 300 GHz (free-space wavelengths between 1 and 1000 mm). Within these frequencies lie the UHF, SHF, and EHF radio frequency bands.

Radars operate at microwave frequencies. Radiance is a radiometric term for the rate at which radiant energy in a set of directions confined to a unit solid angle around a particular direction is transferred across unit area of a surface (real or imaginary) projected onto this direction.

Passive sensor that measures the intensity of microwave radiation (0.3 cm-30 cm) within a specific field of view.

Atmospheric scattering caused by large particles such as dust, pollen, smoke, and water droplets. This is more prevalent in the lower atmosphere, from 0 to 5 km.

MCRs evaluate the feasibility of the proposed mission concept(s) and its fulfillment of the program's needs and objectives. MCRs also determine whether the maturity of the concept and associated planning are sufficient to begin Phase A.

MDRs evaluate the credibility and responsiveness of the proposed mission/system architecture to the program requirements and constraints, including available resources. MDRs also determine whether the maturity of the project's mission/system definition and associated plans are sufficient to begin Phase B.

MRRs evaluate the readiness of the program and its projects, ground systems, personnel, and procedures for a safe and successful launch and flight/mission.

The MRTP documents the strategy that will be used to verify and ensure that all system components working together meet design specifications and requirements for the mission.

Mixing ratio is the number of molecules of a specific type in a mixture relative to that of all other components. In Earth observation, mixing ratio usually refers to the mass ratio of water which is the mass of water divided by the mass of dry air in a given volume of air.

An investigative technique that uses a mathematical or physical representation of a system or theory that accounts for all or some of its known properties. Models are often used to test the effects of changes of system components on the overall performance of the system.

A composite of two or more images put together to create one image.

 Direction toward the center of the Earth, i.e., directly down.

NGAP provides a NASA-compliant, secure, cloud-based Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS) for hosting Earth Observing System Data and Information System (EOSDIS) applications.

NRT Data are those that are available for use with a specified (small and application dependent) latency, which is typically 3 hours for meteorological applications. See LANCE.