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.

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.

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.