Technology Readiness Levels (TRL) are a method of estimating the technology maturity of Critical Technology Elements (CTE) of a program during the acquisition process. They are determined during a Technology Readiness Assessment (TRA) that examines program concepts, technology requirements, and demonstrated technology capabilities.
Definition: Technology Readiness Levels (TRL) are a method used to measure and assess the maturity of a particular technology.
Purpose of Technology Readiness Level (TRL)
The purpose of Technology Readiness Levels (TRL) is to measure the maturity of technology components for a system. The measurement allows project personnel an understanding of how much development a certain technology needs before being utilized. A TRL rating helps in measuring the progress of a project.
Technology Readiness Level (TRL) Scale
TRL is based on a scale from 1 to 9 with 9 being the most mature technology. The use of TRLs enables consistent, uniform, discussions of technical maturity across different types of technologies. Decision authorities will consider the recommended TRLs when assessing program risk. [1,2]
|1||Basic principles observed and reported||Lowest level of technology readiness. Scientific research begins to be translated into applied research and development. Examples might include paper studies of a technology’s basic properties.|
|2||Technology concept and/or application formulated.||Invention begins. Once basic principles are observed, practical applications can be invented. Applications are speculative and there may be no proof or detailed analysis to support the assumptions. Examples are limited to analytic studies.|
|3||Analytical and experimental critical function and/or characteristic proof of concept.||Active research and development is initiated. This includes analytical studies and laboratory studies to physically validate analytical predictions of separate elements of the technology. Examples include components that are not yet integrated or representative.|
|4||Component and/or breadboard validation in laboratory environment.||Basic technological components are integrated to establish that they will work together. This is relatively “low fidelity” compared to the eventual system. Examples include the integration of “ad hoc” hardware in the laboratory.|
|5||Component and/or breadboard validation in relevant environment.||The Fidelity of breadboard technology increases significantly. The basic technological components are integrated with reasonably realistic supporting elements so it can be tested in a simulated environment.|
|6||System/subsystem model or prototype demonstration in a relevant environment.||A representative model or prototype system, which is well beyond that of TRL 5, is tested in a relevant environment. Represents a major step up in a technology’s demonstrated readiness.|
|7||System prototype demonstration in an operational environment.||Prototype near, or at, planned operational system. Represents a major step up from TRL 6, requiring the demonstration of an actual system prototype in an operational environment such as an aircraft, vehicle, or space.|
|8||Actual system completed and qualified through test and demonstration.||Technology has been proven to work in its final form and under expected conditions. In almost all cases, this TRL represents the end of true system development. Examples include developmental test and evaluations of the system in its intended weapon system to determine if it meets design specifications.|
|9||Actual system has proven through successful mission operations.||The actual application of the technology in its final form and under mission conditions, such as those encountered in operational test and evaluation. Examples include using the system under operational mission conditions.|
Systems Engineering use of Technology Readiness Level (TRL)
The primary systems engineering objective is to gain sufficient technical knowledge to develop the program’s System Requirements Document (SRD) and to verify that the system solution(s) required technology is sufficiently mature, has a TRL 6 or above, before proceeding into an end-item design or Milestone B. 
The Technology Development Strategy (TDS) will describe how a program plans to mature its CTE before proceeding into Milestone B. After Milestone B, a technology maturation plan/strategy should be part of the Engineering and Manufacturing Development (EMD) Phase Acquisition Strategy for those CTE that requires additional concurrency and technological development to achieve a higher TRL. 
Technology Readiness Assessment of Technology Readiness Levels (TRL)
While a Technology Readiness Assessment (TRA) uses Technology Readiness Levels (TRL) as key metrics for the evaluation of each technology, an assessment is more than just a single number at only single point in time. It is a compilation of lower-level assessments that could span several years, based on the program schedule and complexity of the development.
Evaluations can help gauge the progress of technology development, inform program plans, and identify potential concerns for decision-makers throughout acquisitions. Conducting TRAs periodically and during the earlier phases of development can identify potential concerns before risks are carried into the later and more expensive stages of system development.
TRAs can also facilitate communication between technology developers, program managers, and acquisition officials throughout development and at key decision points by providing a common language for discussing technology readiness and related technical risks. Finally, TRA results can inform other assessments and planning activities, such as cost and schedule estimates, risk assessments, and technology maturation plans. 
The Technology Readiness Assessment Deskbook – Appendix C, is the best source of TRL information. It covers:
1. Overview of TRL
2. Assessing Hardware Critical Technology Elements (CTE)
3. Assessing Software Critical Technology Elements (CTE)
Technology Readiness Assessment Calculator
The technology readiness assessment calculator was developed by the US Air Force to assist in the process of determining appropriate technology readiness levels (TRL). This calculator provides a technology maturity assessment at a particular time in its development.
Calculator: Technology Readiness Assessment Calculator
Instructions: Technology Readiness Assessment Instructions
Difference Between Technology Readiness Level (TRL) and Manufacturing Readiness Level (MRL)
The difference between Technology Readiness Level (TRL) and Manufacturing Readiness Levels (MRL) is:
- Manufacturing Readiness Levels (MRL): are used to assess the maturity of a given technology, system, subsystem, or component from a manufacturing perspective.
- Technology Readiness Level (TRL): are used to assess the maturity of individual technology.
Manufacturing readiness and technology readiness go hand-in-hand. MRLs, in conjunction with Technology Readiness Levels (TRL), are key measures that define risk when technology or process is matured and transitioned to a system. It is quite common for manufacturing readiness to be paced by technology readiness or design stability. Manufacturing processes will not be able to mature until the product technology and product design are stable.
- There’re different definitions of Technology Readiness Levels, so make sure you follow the one that’s specific to your program or R&D project.
AcqLinks and References:
-  Defense Acquisition Guidebook (DAG) – Chapter 10
-  Technology Readiness Assessment Deskbook – Appendix C
-  GAO Technology Readiness Assessment Guide – Aug 2016
- Technology Readiness Assessment Calculator
- Technology Readiness Assessment Instructions
- TRL Cheat Sheet