MILDENHALL, ENGLAND, April 1954April 1954

On April 26, 1954, an aluminum sphere about the size of a beach ball fell to earth near RAF Station Mildenhall in England. The object was hollow, weighed only six ounces, and measured roughly sixteen inches across. Attached to it by twine was a five-foot square piece of coarse fabric, and remnants of a ruptured balloon hung from that fabric. The sphere itself bore the printed word "HARMLESS" in yellow grease pencil. The most telling clue was stamped on the balloon material: "Made in England."

Air Force investigators from the UK District Office of Special Investigations examined the object after it landed in a tree near the base. They called RAF Station Duxford and other military facilities across the United Kingdom trying to identify its source. Several people who handled or heard about the object volunteered their opinions that it had been used for radar tracking, a purpose many radar testing stations employed balloons and suspended devices for.

The investigation concluded the object was a radar tracking target, essentially an experimental device designed to help radar operators practice spotting and following targets. Since it was manufactured in England, the Air Force believed it had been launched by a radar station somewhere in the United Kingdom. The file notes that no investigation was requested by the commander at Mildenhall, and the matter was forwarded to the Air Technical Intelligence Center for final assessment.

The complete case file, including two black-and-white photographs of the recovered object, is reproduced below as held by the National Archives, comprising 8 pages.