Air Intelligence Information Report IR-8-52: Unidentified Radar Target, Northern Kyushu, 18 December 1952

On 18 December 1952, at approximately 0828 hours, personnel at Detachment 7 of the 527th AC&W Group in Northern Kyushu, Japan, detected an unidentified radar target. The target was tracked for a duration of nine minutes on an AN/MPS-5 radar scope. The object, estimated to be the size of a B-29 aircraft, was initially observed at 300 knots and reached an estimated speed of 1040 knots by the final plot. The flight path varied from an initial course of 270 degrees to 312 degrees. Five other targets were present on the scope at the time, all of which were identified as USAF aircraft. A/3c Ronald L. Keene, who was operating the PPI console, reported that he initially observed the target at 230 degrees at 165 miles and, after observing its rapid movement, brought it to the attention of his crew chief, A/2c Jimmy P. McCoy. The weather conditions in the area included a strong subsidence inversion at 6000 feet with a temperature of 6 degrees centigrade. The official intelligence assessment, signed by Colonel George D. Hastings, concluded that the contact was not confirmed as a bona-fide target. It was suggested that the unusual speeds and the nature of the target were likely the result of radar wave refraction caused by the strong temperature inversion, combined with potential human error in the plotting of a normal friendly aircraft return. The sighting was officially categorized as an unknown.