ITAZUKE AFB, JAPAN, December 1952December 1952

On December 18, 1952, radar operators at Detachment #7 of the 527th Air Control and Warning Group, located in Northern Kyushu, Japan, detected an unidentified target on their radar scope. The object appeared roughly the size of a B-29 bomber and left no visible trace or trail on the radar. It was tracked for nine minutes as it crossed the northern Kyushu area.

The radar operators plotted five separate positions of the target between 0028 and 0037 hours (12:28 a.m. and 12:37 a.m.). The object's speed appeared to increase dramatically during the nine-minute observation, starting at around 300 knots on the first detection and climbing to an estimated 1,040 knots on the final plot. The course varied from 270 degrees (roughly west) on the initial plot to 312 degrees (northwest) at the final position. One radar operator, Airman L. Kemp, estimated the speed exceeded 1,000 miles per hour by the time the target left the scope. Five other radar targets visible at the same time were identified as U.S. Air Force aircraft and posed no mystery.

The weather conditions at the time were variable, with cloud coverage ranging from 50 to 70 percent at altitudes between 4,000 and 5,000 feet. A strong temperature inversion (a layer of warm air trapping cooler air below it) was noted at 6,000 feet with a temperature of 6 degrees Celsius. No interception was attempted, and the radar equipment was operating normally throughout the sighting.

The investigating officers offered a possible explanation. The preparing officer noted that refraction of radar waves through the strong atmospheric inversion could have accounted for the unusual phenomena and apparent high speed. A comment from D/I FEAF (the Air Force's intelligence director in the Far East) added that refraction through the inversion combined with timing errors in plotting a normal friendly aircraft return might explain the reported speeds. However, the comment also noted that the contact had not been confirmed as a genuine target. The Air Force's final evaluation of this case was "unknown." The full case file, comprising seven pages, is reproduced below as held by the National Archives.