"NASA space missions are more ambitious and require the development and integration of more advanced and complex scientific instruments and vehicles than ever before. Hardware systems embedded with software challenge traditional ways of viewing and evaluating critical technology. 13 The issues include a lack of distinction among software types (newly developed, reused, and commercial-off-the-shelf), insufficient experience and knowledge when moving from the laboratory to a "relevant" environment, poor oversight during development, and inconsistent definitions of what represents new software technology. In addition, in some cases, it is no longer possible to evaluate the maturity of certain hardware technologies without their embedded software."
"NASA introduced TRLs in the 1970s and DOD introduced TRAs in the 1990s; they have been adopted by other agencies and industry, and internationally as effective tools for facilitating understanding and increasing knowledge about the maturity of critical technologies and their readiness for integration into larger acquisition systems. Some experts, however, have argued that existing assessment tools are not well suited to addressing various areas - including software systems and systems' integration. For example, historically, the TRL scale has not always been understood in terms of what needs to be demonstrated when it comes to software at each of the nine maturity levels, since software development did not start until the later phases of the acquisition life-cycle, such as after critical design review. New assessment tools or variations on existing tools have been developed for these areas and others."