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This is the prepared statement James E. McDonald, a senior physicist at the University of Arizona's Institute of Atmospheric Physics, submitted to the House Committee on Science and Astronautics for its July 29, 1968 Symposium on Unidentified Flying Objects. He draws on hundreds of witness interviews and weighs eight hypotheses. His conclusion is that UFOs are probably extraterrestrial surveillance devices. He argues that scientists have wrongly neglected the subject and urges much more scientific investigation and further Congressional hearings.
“APRO Bulletin”4 pages
4. Radar Propagation Anomalies: In the past twenty years, there have been many instances in which unidentified objects have been tracked on radar, many of them with concurrent visual observations. Some examples have been cited above. It is always necessary to approach a radar unidentified with full knowledge of the numerous ways in which false returns can be produced on radar sets. The physics of "ducting" or "trapping" is generally quite well understood. As with mirages, the allowed angle of elevation of the radar beam can only depart from zero by a few tens of minutes of arc for typically occurring inversions and humidity gradients. Ducting with beam angles in excess of a degree or so would require unheard of atmospheric temperature or humidity gradients. Care must be taken in interpreting that statement, since beam- angles have to be distinguished from angles of elevation of the beam axis. For the latter reason, a beam-axis elevation of, say, two degrees still involves emission of some radar energy at angles so low that some may be trapped, yielding "ground returns" despite the higher elevation of the axis. All such points are well described in an extensive literature of radar propagation physics. In addition to trapping and ground return effects, spurious returns can come from insects, birds, and atmospheric refractive-index anomalies that generate radar echoes termed "angels". These are low-intensity returns that no experienced operator would be likely to confuse with the strong return from an aircraft or other large metallic object. Also, other peculiar radar effects such as interference with other nearby sets, forward scatter from weak tropospheric discontinuities (see work of Atlas and others), and odd secondary reflections from ground targets need to be kept in mind. When one analyzes some of the famous radar-tracking cases in the UFO literature, none of these propagation anomalies seem typical as accounting for the more interesting cases. Several examples have already been discussed above (Cases 32, 35, 36, 37, 38, 39). SUMMARY AND RECOMMENDATIONS: In summary, I wish to emphasize that my own study of the UFO problem has convinced me that we must rapidly escalate serious scientific attention to this extraordinarily intriguing puzzle. I believe that the scientific community has been seriously misinformed for twenty years about the potential importance of UFOs. I do not wish here to elaborate on my own interpretation of the history behind that long period of misinformation; I only wish to urge the Committee on Science and Astronautics to take whatever steps are within their power to alter this situation without further delay. The present Symposium is an excellent step in the latter direction. I strongly urge your Committee that further efforts in the same direction be made in the near future. I believe that extensive hearings before your Committee, as well as before other Congressional committees having concern with this problem, are needed. The possibility that the Earth might be under surveillance by some high civilization in command of a technology far beyond ours must not be overlooked in weighing the UFO problem. I am one of those who lean strongly towards the extraterrestrial hypothesis. I arrived at that point by a process of elimination of other alternative hypotheses, not by arguments based on what I would call "irrefutable proof." I am convinced that the recurrent observations by reliable citizens here and abroad over the past twenty years cannot be brushed aside as nonsense, but rather need to be taken extremely seriously as evidence that some phenomenon is going on which we simply do not understand. Although there is no current basis for concluding that hostility and grave hazard lie behind the UFO phenomenology, we cannot be entirely sure of that. For all of these reasons, greatly expanded scientific and public attention to the UFO problem is urgently needed. The proposal that serious attention be given to the hypothesis of an extraterrestrial origin of UFOs raises many intriguing questions, only a few of which can be discussed meaningfully. A very standard question of skepticism is
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