Technology Readiness Levels (TRL) are different points on a scale used to measure the progress or maturity level of a technology. The scale ranges from 1 to 9, where TRL 1 is the lowest and TRL 9 is the highest. When a technology is at TRL 1, scientific research is beginning and those results are being translated into future research and development, while at TRL 9 the technology has already been proven to work during a flight mission in space.
Each technology project is evaluated against the parameters for each technology level and is then assigned a TRL rating based on the projects progress.
While the implementation of the concept is a well-established standard, not only in ESA and NASA, but also in many Agencies and Industry around the world, different definitions or interpretations were used. ESA uses the ISO 16290 TRL Scale.
ESA’s different research and development Programmes and Projects work across a range of TRLs. (Further info also available via the ECSS website - document ECSS-E-HB-11A (registration is required).)