ESA definition[edit]
Instruments and spacecraft sub-systems technical maturity with respect to a specific
space application are classified according to a "Technology Readiness Level" (TRL) on
a scale of 1 to 9.
Technology Readiness Levels in the European Space Agency (ESA)[5]
Technology Readiness
Description
Level
TRL 1.
Basic principles observed and reported
TRL 2.
Technology concept and/or application formulated
Analytical and experimental critical function and/or
TRL 3.
characteristic proof-of-concept
Component and/or breadboard functional verification in
TRL 4.
laboratory environment
Component and/or breadboard critical function verification in
TRL 5.
relevant environment
Model demonstrating the critical functions of the element in a
TRL 6.
relevant environment
Model demonstrating the element performance for the
TRL 7.
operational environment
Actual system completed and accepted for flight ("flight
TRL 8.
qualified")
Actual system "flight proven" through successful mission
TRL 9.
operations
European Commission definition[edit]
Technology Readiness Levels in the European Commission (EC)[6]
Technology
Description
Readiness Level
TRL 1.
basic principles observed
TRL 2.
technology concept formulated
TRL 3.
experimental proof of concept
TRL 4.
technology validated in lab
technology validated in relevant environment (industrially
TRL 5.
relevant environment in the case of key enabling technologies)
technology demonstrated in relevant environment (industrially
TRL 6.
relevant environment in the case of key enabling technologies)
TRL 7.
system prototype demonstration in operational environment
TRL 8.
system complete and qualified
actual system proven in operational environment (competitive
TRL 9.
manufacturing in the case of key enabling technologies; or in
space)