Operation Close Encounter — File 17/26/AIR

Operation Close Encounter was an investigation conducted by the Royal Australian Air Force (RAAF) in response to a series of unidentified radar contacts reported by the Area Approach Control Centre (AACC) at Mascot, Sydney, in June and July 1983. The AACC reported that these contacts exhibited movements consistent with aircraft and suggested they were man-made objects. In response, RAAF Base Williamtown was directed to investigate. 3CRU (3 Control and Reporting Unit) initiated round-the-clock surveillance and placed Mirage interceptors on alert. An investigative team of Air Defence Controllers was dispatched to the AACC to analyze the radar data. The team discovered that the reported contacts were not physical objects but were instead the result of radar interference within the Sydney Route Surveillance Radar (RSR) processor, a phenomenon known as 'running rabbits.' This interference was being misinterpreted by AACC operators as rapidly moving aircraft. The investigation team confirmed this by comparing the AACC's radar display with raw video from the maintenance radarscope, which showed no corresponding targets. The operation resulted in significant accrued overtime for 3CRU personnel and disrupted planned maintenance and training. The report concludes that the sightings were not genuine unidentified flying objects and recommends improved data-linking between radar sensors and better communication between operational and technical staff to prevent similar false alarms in the future.