TRL 1 - Basic principles observed and reported. Lowest level of technology readiness. Scientific research begins to be translated into applied research and development.
TRL 2 - Technology concept and/or application formulated. Once basic principles are observed, practical applications can be invented and R&D started. Applications are speculative and may be unproven.
TRL 3 - Analytical and experimental critical function and/or characteristic proof-of concept. Active research and development is initiated, including analytical / laboratory studies to validate predictions regarding the technology.
TRL 4 - Component and/or breadboard validation in laboratory environment. Basic technological components are integrated to establish that they will work together.
TRL 5 - Component and/or breadboard validation in a relevant environment. The basic technological components are integrated with reasonably realistic supporting elements so it can be tested in a simulated environment.
TRL 6 - System/subsystem model or prototype demonstration in a relevant environment. A representative model or prototype system is tested in a relevant environment.
TRL 7 - System prototype demonstration in relevant environment. A prototype system that is near, or at, the planned operational system.
TRL 8 - Actual system completed and “qualified” through test and demonstration. In an actual system, the technology has been proven to work in its final form and under expected conditions.
TRL 9 - Actual system “proven” through successful mission operations. The system incorporating the new technology in its final form has been used under actual mission conditions.