Difference in intensity between all incoming energy and all outgoing energy carried by both shortwave and longwave radiation.

NetCDF format that uses the HDF5 data storage model.

Nitric acid (HNO3) is a water soluble, acidic gas.

In the atmosphere, nitric acid is formed by the conversion of nitrogen monoxide into nitrogen dioxide, and ultimately into nitric acid. It readily reacts with atmospheric water to produce acidic precipitation. Nitric acid also reacts with gaseous ammonia to form particulate or aerosol nitrate, which in turn is removed by wet and dry deposition of the particles. In the clean background troposphere, its removal in precipitation acts as a sink for odd hydrogen and nitrogen compounds and limits the formation of ozone.

The goal of the North American Land Data Assimilation System (NLDAS) is to construct quality-controlled, and spatially and temporally consistent, land-surface model (LSM) datasets from the best available observations and model output to support modeling activities.

Collection of products that are generated in response to a user's request. Such products could either be pre-defined or not.

ORRs evaluate the readiness of the program, including its projects, ground systems, personnel, procedures, and user documentation. ORRs also operate the flight system and associated ground systems in compliance with program requirements and constraints during the operations phase.

Operations Agreements are even lower level, more detailed interface documents that are created to help define the operations use of the interfaces, including such things as addresses, phone numbers, and names of responsible personnel. These documents are not intended for project-level development and control.

Loss of ozone through natural breakdown and anthropogenically produced chemical reactions.

A region of rapid, dramatic ozone depletion over Antarctica during the polar spring. Confined to south of 55° latitude. Disperses soon after temperatures rise above -80° C.

 A predetermined set of preselected, predefined and prearranged data (granules) organized for distribution.

A color lookup table that specifies which color to associate with each pixel value on the screen. A palette consists of an array of 256 RGB (Red-Green-Blue) colors.

A measurable or derived variable occurring in the physical or digital world. Variable and Parameter are used interchangeably. GCMD uses the term variable and NSIDC DAAC uses the term parameter.

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

Damaging photochemical oxidants that are very irritating to the eyes and throat. Represented as RC(O)OONO₂ where R denotes a hydrocarbon ring or chain.  They are markers for the source of volatile organic compounds (VOC) as being either biogenic or anthropogenic, which helps in the study of the effects of pollution. 

Also known as: photodissociation, photodecomposition, photofragmentation.

A chemical process driven by the Sun's radiation in which the molecules of a compound are broken down by the absorption of light.

Chemical process driven by solar energy in which CO₂ and H₂O, in the presence of chlorophyll, are converted to oxygen and carbohydrates. Oxygen and water vapor are released in the process.

The polar night jet is a stream of high velocity winds in the upper stratosphere and mesosphere. The polar night jet forms in late autumn, and generally encloses the region of the polar night, which occurs when there is no solar radiation reaching the polar regions.

High, thin clouds composed of nitric acid and water that form in the coldest regions of the stratosphere when temperatures drop below -80°C. Ice crystal surfaces within these clouds are efficient in converting inert chlorine reservoirs, such as ClONO₂ and HCl, into reactive chlorine compounds.

Wind region around the North or South pole.The southern vortex is a well formed circular to oblong mass of extremely cold, stagnant air, held in place by the ocean surrounding the Antarctic land mass and a strong westerly circulation pattern produced by the coriolis effect. 

The northern vortex is not as distinct because the Arctic is a frozen ocean surrounded by rugged land masses, which cause the circulating winds to encounter a variety of temperatures.

Uniform and nonrandom elliptical, circular, or linear variation of a wave, characteristic in light or other radiation.

PFARs evaluate how well mission objectives were met during a human space flight mission. PFARs also evaluate the status of the flight and ground systems, including the identification of any anomalies and their resolution.

PLARs evaluate the in-flight performance of the program and its projects. PLARs also determine the program's readiness to begin the operations phase of the life cycle and transfer responsibility to the operations organization.

PDRs evaluate the completeness/consistency of the program's preliminary design, including its projects, in meeting all requirements with appropriate margins, acceptable risk, and within cost and schedule constraints, and to determine the program's readiness to proceed with the detailed design phase of the program.

Preservation covers all processes and operations on individual or multi-mission data sets for ensuring the technical and intellectual survival of space data sets and their metadata through time. It grants dataset integrity, its discoverability and accessibility, and facilitates its use and reuse in the long term. 

Preservation is one of the tasks of data curation. Examples are data record improvement and consolidation.

The processing function generates higher-level products from lower level products and auxiliary products. The processing is performed by core algorithms supplemented by administrative functions (e.g. formatting). The algorithms are version controlled. Processing is able to produce the desired products systematically or on request.

Raw Data 
The physical telemetry payload data as received from the satellite, i.e. a serial data stream without de-multiplexing. 

Level 0 
Reconstructed unprocessed data at full space-time resolution with all available supplemental information to be used in subsequent processing (e.g. ephemeris, health and safety) appended. 

Level 1A 
Reconstructed unprocessed data at full resolution, time-referenced, and annotated with ancillary information, including radiometric and geometric calibration coefficients and geo-referencing parameters (e.g. ephemeris) computed and appended but not applied to the Level 0 data. 

Level 1B 
Radiometrically corrected and calibrated data in physical units at full instrument resolution as acquired. Level 1C L1B data orthorectified, re-sampled to a specified grid 

Level 2 
Derived geophysical parameters (e.g. sea surface temperature, leaf area index) at the same resolution and location as Level 1 source data. 

Level 3 
Data or retrieved geophysical parameters which have been spatially and/or temporally re-sampled (i.e. derived from Level 1 or 2 products), usually with some completeness and consistency. Such re-sampling may include averaging and compositing. 

Level 4 
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).

1.
Electronic data package distributable to users; content is derived from instrument data via processing involving ancillary and auxiliary data. Products may comprise metadata and browse images. 

2.
A product may be part of a collection – a distinction useful for archiving and cataloging purposes. 

3.
The term product may be used to denote a product type, such as e.g. ENVISAT_ASAR_L1B_PRI data. 

4.
End users may distinguish between (input, "raw") data and products, i.e. the derived geophysical parameters.

Useful references to published articles about the use of the data and user feedback received by the science and instrument teams about the products. Includes reports of any peculiarities or notable features observed in the products.

The specific implementation of global attributes, dimensions, groups, variables, and variable-level attributes in a data product, which is specified via the Product Format Specification (PFS) file.

The Product Generation Algorithm, the version of source code used to produce the data products, need to be carefully preserved and recorded, along with version history, as well as:

• The algorithm's theoretical (scientific and mathematical) basis,
• How the algorithm is numerically implemented, including possible issues with computationally intensive operations,
• A description of the outputted data products at a level of detail to determine if the product met specified product requirements,
• A description of all assumptions that have been made concerning the algorithm performance estimates and any limitations,
• A list of various error estimates and the error budget.

Description of the impact to product quality due to issues with computationally intensive operations (e.g., large matrix inversions, truncation and rounding).

A document that provides the technical specifications relating to the formatting and content of a particular data product.

Names of key science team leads and product team members (development, help desk and operations), roles, performing organization, contact information, sponsoring agencies or organizations and comments about the products.

PRRs evaluate the readiness of system developer(s) to produce the required number of systems within defined project constraints for projects developing multiple similar flight or ground support systems. PRRs also evaluate the degree to which the production plans meet the system's operational support requirements.

The project plan contains the technical approaches and management plans to implement the project requirements. It defines, at a high level, the scope of the project, the implementation approach, the environment within which the project operates, and the baseline commitments of the program and project. (From NPR 7120.5D)

The information that documents the history of the content information. This information tells the origin or source of the content information, any changes that may have taken place since it was originated, the inputs responsible for a product, what versions of algorithms used, who has had custody of it since it was originated etc. Examples of provenance information could be the principal investigator who recorded the data, and the information concerning its storage, handling, and migration.

One or more unique variables within a data file that show what data quality assessments have been performed as well as diagnostics on various aspects of quality. A quality flag can be a byte value with each bit representing a pre-defined quality verification criterion provided as a Boolean expression.

1. A quality indicator shall provide sufficient information to allow all users to readily evaluate the “fitness for purpose” of the data or derived product. A Quality Indicator may be a number, set of numbers, graph, uncertainty budget, or a simple “flag”.
2. One or more unique variables within a data file whose numerical value shows the overall quality of a geophysical measurement. The numerical value should be on a predefined numerical scale. For example, uncertainty per pixel (or measurement), percent cloud cover (in a scene).

Secondary data required to assess the primary data set’s fitness for purpose, e.g. calibration and validation data and quality control results.

The quasi-biennial oscillation (QBO) is a periodic variation in the prevailing wind direction (either easterly or westerly) in the stratosphere above Earth's tropical region. The wind direction changes every 14 months, creating a 28-month cycle. 

When the QBO is in an easterly phase, it can weaken the Arctic jet stream and cause a sudden stratospheric warming. When the QBO is in a westerly phase, it can create a strong jet stream and a stable polar vortex.

A data product, usually related to a Level 1 or higher Standard Data Product, which is generated and distributed in near-real time.

See: Processing Levels

Dominant form of light scattering in the upper atmosphere, which produces the blue color of the sky. It is caused by atmospheric particulates that have very small diameters relative to the wavelength of the light, such as dust particles or atmospheric gases like nitrogen and oxygen.

The ratio of reflected radiation to incident radiation on a surface. Virtually all remote sensing measurements in the visible range (~400 nm - 700 nm) can be converted to reflectance, which is a standard optical property related to the substance or surface from which light is reflected. Because reflectance can be wavelength-specific due to absorption and scattering, reflectance is a key and basic quantity in using remote sensing to determine the identity of anything that reflects light.

Remote sensing reflectances (Rrs) are defined as the at-surface spectral remote-sensing reflectances observed by the satellite instrument after atmospheric correction. The units of Rrs are sr^-1.

Ratio of the intensity of the total radiation reflected from a surface to the total radiation incident on the surface.

Reprocessing is a part of processing where a complete product collection is systematically generated to obtain a new revision using archived lower level products. Reprocessing is normally initiated after an improved processing algorithm is released. Reformatting could be considered or conducted as part of a re-processing exercise.

Requirements documents are detailed requirements allocated from the project to the next lower level of the project.

SMSRs prepare Agency safety and engineering management to participate in program final readiness reviews preceding flights or launches, including experimental/test launch vehicles or other reviews as determined by the Chief, Safety and Mission Assurance. SMSRs also provide the knowledge, visibility, and understanding necessary for senior safety and engineering management to either concur or nonconcur in program decisions to proceed with a launch or significant flight activity.

The angle between the position of a satellite and the zenith, which is the point directly over the observed target.

Subset of an instrument acquisition data segment, cut by time i.e. across-swath.