Weather balloon
From Memory Alpha, the free Star Trek reference.
A weather balloon was a device used on 20th century Earth by the US Army Air Corps and other agencies to assess wind speed and other meteorological conditions.
In 1947, according to the US Air Corps, a farmer from Roswell, New Mexico and later an Air Corps officer incorrectly identified a crashed weather balloon as fragments of a UFO. At least, that is the official story released to the press. (DS9: "Little Green Men")
