There are two levels to evaluating the operational effectiveness of UAV systems. At the highest level are the Critical Operational Issues (COIs). At the lowest level, there are specific performance characteristics, such as time on station at a given range, the probability of detecting a target, or the level of target location error. Specificperformance characteristics are usually utilized within requirements documents due to the perceived ease of measuring and evaluating these types of metrics; however, this approach presents its own set of unique problems as described below.