Essential procedures required to conduct a successful long duration space mission post-flight debrief are described. The purpose of the debrief is to accumulate meaningful long duration mission habitability data. The data is translated into candidate human engineering “lessons learned” that are reviewed using predefined acceptance criteria to determine the scope and generalization potential of the data. Candidate lessons learned that satisfy the acceptance criteria are reviewed by human engineering specialists and crewmember representatives to achieve consensus. Lessons learned knowledge is evaluated, shared, and when applicable, incorporated into future space operations / habitability systems. The goals of applying International Space Station (ISS) Phase I human engineering lessons learned to future long duration missions are to enhance crew operations and system effectiveness.