During a series of tests to provide operational and technical data for evaluating the capabilities of surface-based air defense systems against attacks by low-altitude high-performance aircraft, the capabilities of ground observers to detect and estimate the range to aircraft flying attack missions against prebriefed ground targets were examined. Observer performance was obtained for three aircraft flying three programmed speeds and two programmed altitudes. Sixteen observers searched a 180 deg sector for each trial, with early warning of an aircraft approach being provided for some trials. Three real time events--time at detection, time when the aircraft was at the estimated inbound range, and time when aircraft was at the estimated outbound range--were recorded for each observer for each trial. (Author)).