HOKKAIDO, JAPAN, February 1953February 1953

On February 7, 1953, five U.S. Air Force personnel stationed at Misawa Air Base in Hokkaido, Japan saw an unidentified object in the night sky. The object was a bright light that changed colors rapidly, shifting from red to green to white. Observers estimated it was about 15 degrees above the horizon and located roughly due east of the base, on a bearing of 91 degrees. Two of the five witnesses reported that the object was moving, though observers disagreed about the type of movement. One witness noted that some thought it was whirling, some said it was stationary, and others believed it was in orbit. The object was bright, noticeably brighter than the evening star, and two observers reported that light appeared to beam from the lower side of the object's bottom. The witnesses watched for approximately 35 minutes.

During the visual sighting, a radar blip appeared on the station's radar screen briefly. The radar operators recorded the target at 85 nautical miles away, but only saw it for a short time on a single sweep. Despite searching the area, the radar operators could not relocate the target.

An Air Force intelligence officer who arrived at the scene directed the radar antenna to lock onto the object and took a bearing of 207 degrees with a tolerance of plus or minus 4 degrees. The object appeared to be about 15 degrees above the horizon, though the officer noted this was only a rough estimate made without proper instruments. The Air Force's official analysis concluded that the sighting most likely was a lighted weather balloon, probably launched from a Soviet weather station in the islands near Hokkaido, noting that the time of the sighting matched when weather balloons were normally launched. The weather at the time was clear, which the analysis cited as consistent with excellent visibility for observing a balloon.

The full case file is reproduced below as held by the National Archives in 8 pages.