Existing cognitive performance test batteries consist of synthetic tasks that, while they may probe isolated cognitive functions, provide an incomplete and unconvincing picture of an individual's true cognitive capacity within the total context of space missions. In essence, they are 'laboratory' measures that appear unrelated to the real-world environment. This leads to user non-compliance or rejection. The present proposal describes a technique for integrating traditional cognitive performance measures with assessment of the system and mission in which the individual must operate. This yields quantified measures of the person's cognitive ability to perform specific jobs in space. Specifically, an entertaining and scientifically rigorous assessment tool is integrated with a sleep/fatigue model and a quantified workload estimate for each task. This is accomplished by selecting tests based on task analyses of what the astronaut actually has to do, using the Fatigue Avoidance Scheduling Tool (FAST) to predict performance capacity as a function of sleep/rest, and integrating a mathematical vector to quantify the workload of specific tasks. The resulting "Person-System-Mission (PSM) index" provides a totally new and unique way not only to assess present cognitive capability, but to diagnose specific causes of decrement, and to suggest remedial actions.