Introduction (The lure of local SETI: Fifty years of field experiments)

With the commemoration in October 2007 of the Sputnik launch, space exploration celebrated its 50th anniversary. Despite impressive technological and scientific achievements the fascination for space has weakened during the last decades. One major contributing factor has been the gradual disappearance of mankind's hope of discovering intelligent extraterrestrial life within its close neighbourhood. The search for extraterrestrial intelligence (SETI) initiated almost 50 years ago has equally contributed to this disenchantment, as it failed to intercept any sign of radio or optical transmission from an extraterrestrial intelligence. It follows that the most profound philosophical question of humankind: "Are we alone in the universe?", still remains unanswered today. Not for everyone. In striking contrast and since the middle of the 20th century, a non-negligible proportion of the population believes that intelligent beings from other worlds do exist and visit Earth through space vehicles popularly called Unidentified Flying Objects (UFOs). Although that most of the sightings can be attributed to the misidentification of natural phenomenon or man-made objects and that Ufology (study of UFOs) has failed to provide any irrefutable scientific evidence, the continuation of UFO observations and the existence of a residue of cases remaining unexplained after analysis call for a legitimate consideration of the topic and some appropriate study. Avoiding the usual controversy, speculation and sensationalism, this paper provides an objective, historical perspective on a cross section of scientific field experiments deployed in the USA, Canada and Europe over the last 60 years aimed at proving the physical reality of the UFO Phenomena and potentially the presence of probes of extraterrestrial origin on Earth.