Project 10073 Record Card — Knoxville, Tennessee, October 21, 1952

On October 21, 1952, a weather observer at the Weather Bureau Airport Station in Knoxville, Tennessee, reported an encounter with unexplained aerial phenomena while tracking a 100-gram pibal balloon. Fifty-seven minutes after the release of the balloon, the observer noted six white or whitish, round objects appearing in the theodolite's field of vision. These objects maintained a loose formation at an altitude of approximately 54,347 feet MSL, with an elevation angle of 36.5 degrees and an azimuth of 267.6 degrees. The observer reported that the objects appeared to be roughly the same size as the balloon. During the one-and-a-half to one-and-three-quarter minute observation, the objects were seen executing a long, shallow dive toward the rising balloon, as if to investigate it. Subsequently, the formation passed the balloon and pulled up at a sharper angle than their initial approach, while simultaneously increasing their speed. The pibal balloon eventually disappeared from view at 58,022 feet MSL, with the observer noting it could have burst. The incident was documented on a Project 10073 record card, which classified the event as 'Unknown.' The investigator's notes indicate that the sighting was made using a theodolite and explicitly mention that two other similar observations were present in the project's files.