has generally become synonymous with alien spacecraft; however, the term ETV (extra-terrestrial vehicle) is sometimes used to separate this explanation of UFOs from totally earthbound explanations. Investigations of reports UFOs have been subject to investigations over the years that varied widely in scope and scientific rigor. Governments or independent academics in the United States, Canada, the United Kingdom, Japan, Peru, France, Belgium, Sweden, Brazil, Chile, Uruguay, Mexico, Spain, and the Soviet Union are known to have investigated UFO reports at various times. No official government investigation has ever publicly concluded that UFOs are indisputably real, physical objects, extraterrestrial in origin, or of concern to national defense. Among the best known government studies are the ghost rockets investigation by the Swedish military (1946–1947), Project Blue Book, previously Project Sign and Project Grudge, conducted by the USAF from 1947 until 1969, the secret U.S. Army/Air Force Project Twinkle investigation into green fireballs (1948–1951), the secret USAF Project Blue Book Special Report No. 14 by the Battelle Memorial Institute, and the Brazilian Air Force's 1977 Operação Prato (Operation Saucer). France has had an ongoing investigation (GEPAN/SEPRA/GEIPAN) within its space agency Centre national d'études spatiales (CNES) since 1977; the government of Uruguay has had a similar investigation since 1989. Prosaic explanations Studies show that after careful investigation, the majority of UFOs can be identified as ordinary objects or phenomena. The most commonly found identified sources of UFO reports are: astronomical objects (bright stars, bolides, bright planets, and the Moon) aircraft (including military, civilian, and experimental aircraft as well as such peculiarities as aerial advertising, missile and other rocket launches, artificial satellites, re-entering spacecraft including space debris, kites, and various unmanned aerial vehicles often popularly termed "drones") balloons (surveillance balloons, toy balloons, weather balloons, large research balloons) other atmospheric objects and phenomena (birds, unusual clouds, flares) light phenomena (mirages, Fata Morgana, ball lightning, moon dogs, satellite flares, searchlights and other ground lights, etc.) psychological effects (pareidolia, suggestibility and false memories, mass psychogenic disorders, optical illusions, and hallucinations) hoaxes A 1952–1955 study by the Battelle Memorial Institute for the USAF included these categories. An individual 1979 study by CUFOS researcher Allan Hendry found, as did other investigations, that fewer than one percent of cases he investigated were hoaxes and most sightings were actually honest misidentifications of prosaic phenomena. Hendry attributed most of these to inexperience or misperception. Americas Brazil (1952–2016) On October 31, 2008, the National