A target of opportunity is a target "visible to a surface or air sensor or observer, which is within range of available weapons and against which fire has not been scheduled or requested."[1] A target of opportunity comes in two forms; "unplanned" and "unanticipated".[2] Unplanned targets of opportunity are those that fall within mission parameters as appropriate targets but were not included within a mission brief. Unanticipated targets are those that fall outside of mission parameters because their availability was not expected, such as an otherwise high-value target being identified at a location where another unrelated mission is underway.