Ft. Meade, MarylandFebruary 1961

On the night of February 28, 1961, radar operators at Fort George G. Meade detected an unusual target on their screen at 2245 EST (Eastern Standard Time). The object appeared on ground-based radar used for missile tracking at the 35th Artillery Brigade's Missile Master Center. Lieutenant Paul Foster, a radar duty officer, was among the military personnel who tracked the target. According to the file, the object showed unusually high speed, an ability to stand still, and a high rate of change of direction. It appeared at an elevation of approximately 6,300 feet and an azimuth (direction) of approximately 270 degrees (due west). The target remained visible for about twenty minutes before disappearing at roughly the same elevation but at an azimuth of approximately 200 degrees (southwest).

Military investigators interviewed multiple personnel present at the Missile Master Center that night, all rated as reliable. The radar was an AN/FPS-33 set, a sophisticated military system used to track aircraft and missiles. Investigators also collected weather data from the area, including wind aloft readings at various altitudes and sky conditions that night, which were reported as clear with unlimited ceiling and visibility.

An analysis by radar specialists ultimately concluded that the target was probably caused by a temperature inversion (a layer of warmer air trapping cooler air below it, which can bend radar beams and create false signals on radar screens). The specialists noted that erratic false targets are not uncommon when the right temperature inversion conditions exist. Because the behavior of the reported object matched this type of radar artifact, they evaluated it as such. The file notes that equipment malfunction could not be completely ruled out. The Air Force evaluation listed the case as "probably balloon," though the radar analysis suggested atmospheric conditions as the more likely culprit.

The full case file is reproduced below as held by the National Archives, comprising 15 pages.