By 1959, when Cocconi and Morrison were publishing their famous paper s1[12] G. Cocconi, P. Morrison, Searching for Interstellar Communications, Nature magazine, 1959 in which they suggested using radio telescopes to look for communication signals from other technological civilizations in the galaxy, a not insignificant proportion of the population had already concluded that intelligent beings from other worlds did exist and were visiting Earth. Both the North American continent and Europe had been confronted since the end of the 1940s with an important number of observations of UAP, and one of the most favoured explanation was these were space vehicles from extraterrestrial intelligences.
A few years earlier in the summer of 1950, Nobel's prize physicist Enrico Fermi during a visit to Los Alamos facilities posed the famous question "Where is everybody?" This led to what has since been known as the Fermi Paradox s2E. Jones: "'Where is everybody?' An account of Fermi’s question", Los Alamos Technical report LA-10311-MS, 1985. Commenting on a New Yorker magazine cartoon depicting a flying saucer in the background with aliens carrying trash cans, the Italian physicist questioned why if many different extraterrestrial civilizations existed in our galaxy, there was no sign or trace of them. Given the fact that there were billions of sun-like stars older than our sun in our galaxy, there had been plenty of time for life to develop on some planets and for intelligent technological civilizations to develop very advanced interstellar transportation systems. As no evidence of alien radio or optical transmission, spacecraft or technology had been discovered, the question about the likelihood of intelligent extraterrestrial life was debatable.
Obviously the notion of interstellar probes visiting Earth would constitute a neat solution to the Fermi paradox, and
some people might even argue that the accumulation of a large quantity of UFO observations over the past sixty years
is the definitive answer to Fermi’s question. The possibility that some smart extraterrestrial probes could have
already reached our solar system is not as absurd as it sounds at first, not even for the SETI scientists who often
share a very sensitive relationship with the UFO community. Professor A. Tough’s wrote in 1999 "How to achieve
contact: five promising strategies" s3When SETI succeeds: the impact of high information contact, a humanity 3000 knowledge workshop, (1999 seminar).,
a document in which he stressed the need for widening the array of the SETI searches and described among the range of
actions the following one: "Develop and implement rigorous new research designs to study any anomalous phenomena
that could be signs of ETI presence on Earth
".
For Tough some possible ways forward would be to use foolproof laboratory procedures to test whether any physical
traces or artefact supposedly associated with UFOs provide definitive evidence of alien origin. A complementary
possibility would be to set up sophisticated scientific equipment at promising locations in order to discover whether
it is possible to record solid data showing the physical presence of alien probes or spacecraft. Consequently even if
we take the assumption, that true extraterrestrial UFOs have not visited yet us, one might not suppose that this will
remain this way forever. Considering the fact that we do not have the slightest idea of what an extraterrestrial
advanced civilization will turn out to be, likely advanced to a level of knowledge and technology fantastically more
advanced than ours, perhaps even post-biological, we should be ready to investigate all potential promising
possibilities. However a delicate equilibrium needs to be maintained between either being too open-minded and opening
the door to pseudo-science, or immediately dismissing the reports of anomalous phenomena and potentially missing a
genuine manifestation of extraterrestrial visit. Sagan had emphasized this requirement more than thirty years ago:
"The idea of benign or hostile super beings from other planets visiting the earth clearly belongs in such a list of
emotion-rich ideas. There are two sorts of possible self-deceptions here: Either accepting the idea of
extraterrestrial visitation in the face of very meagre evidence because we want it to be true; or rejecting such an
idea out of hand, in the absence of sufficient evidence, because we do not want it to be true. Each of these
extremes is a serious impediment to the study of UFO
" s4C. Sagan, UFO’s—A scientific debate, Cornell University Press, 1969, p. 265..
Because the discovery of and contact with other civilizations would be an unparalleled historic event with potential invaluable benefits for humanity, including the field of unidentified aerospace phenomenon in the SETI strategies and reflecting on new scientific research directions appears essential. In that context, the following section gives an historical perspective on the different strategies and field experiments deployed in the USA, Canada and Europe by governments, researchers and organizations since the beginning of the modern emer- gence of the UFO phenomenon (end of the 1940s). The aim of this information is to provide a potential useful contribution to the definition of any future UAP research programme involving technical equipments and field programmes.