Developed in the 1970s, J. Allen Hynek’s original system of description divides sightings into six categories. It first separates sightings into distant- and close-encounter categories, arbitrarily setting five hundred feet as the cutoff point. It then subdivides these close and distant categories based on appearance or special features:
Nocturnal Lights (NL): Anomalous lights seen in the night sky.
Daylight Discs (DD): Any anomalous object, generally but not necessarily “discoidal”, seen in the distant daytime sky.
Radar/Visual cases (RV): Objects seen simultaneously by eye and on radar.
Hynek also defined three close encounter (CE) subcategories:
CE1: Strange objects seen nearby but without physical interaction with the environment.
CE2: A CE1 case that leaves physical evidence, e.g. soil depressions, vegetation damage, radiations or causes electromagnetic interference.
CE3: CE1 or CE2 cases where occupants or entities are seen.
Later, Hynek introduced a fourth category, CE4, which is used to describe cases where the witness feels he was abducted by a UFO. Some ufologists have adopted a fifth category, CE5, which involves conscious human-initiated contact with extraterrestrial intelligence.
Jacques Vallée has devised a UFO classification system, where the UFO sightings of four different categories are divided into five subcategories:
Close Encounter (CE): As per Hynek.
Maneuver (MA): Trajectory discontinuity in flight.
Fly-by (FB): No observed discontinuity in flight.
Anomaly (AN): Unusual lights or unexplained entities.
The five subcategories can apply to all previous categories of sightings:
Physical effects: for example, radar sighting
Life form or living entity
Reality transformation: witnesses experienced a transformation of their sense of reality (often corresponding to the popular characterization of the incident as an abduction)
Physiological impact: Such as death or serious injury
Thus, the Vallée categorization categorizes cases as MA-2, AN-1, CE-4, for example.
Ufology and UFO reports
In addition to UFO sightings, certain supposedly related phenomena are of interest to some in the field of ufology, including crop circles, cattle mutilations, and alien abductions and implants. Some ufologists have also promoted UFO conspiracy theories, including the alleged Roswell UFO Incident of 1947, the Majestic 12 documents, and UFO disclosure advocates.
Skeptic Robert Sheaffer has accused ufology of having a “credulity explosion”. He claims a trend of increasingly sensational ideas steadily gaining popularity within ufology. Sheaffer remarked, “the kind of stories generating excitement and attention in any given year would have been rejected by mainstream ufologists a few years earlier for being too outlandish.”
Likewise, James McDonald has expressed the view that extreme groups undermined serious scientific investigation, stating that a “bizarre ‘literature’ of pseudo-scientific discussion” on “spaceships bringing messengers of terrestrial salvation and occult truth” had been “one of the prime factors in discouraging serious scientists from looking into the UFO matter to the extent that might have led them to recognize quickly enough that cultism and wishful thinking have nothing to do with the core of the UFO problem.” In the same statement, McDonald said that, “Again, one must here criticize a good deal of armchair-researching (done chiefly via the daily newspapers that enjoy feature-writing the antics of the more extreme of such subgroups). A disturbing number of prominent scientists have jumped all too easily to the conclusion that only the nuts see UFOs”.
Surveys of scientists and amateur astronomers concerning UFOs
In 1973, Peter A. Sturrock conducted a survey among members of the San Francisco chapter of the American Institute of Aeronautics and Astronautics, where 1175 questionnaires were mailed and 423 were returned, and found no consensus concerning the nature and scientific importance of the UFO phenomenon, with views ranging equally from “impossible” to “certain” in reply to the question, “Do UFOs represent a scientifically significant phenomenon?” In a later larger survey conducted among the members of the American Astronomical Society, where 2611 were questionnaires mailed and 1356 were returned, Sturrock found out that opinions were equally diverse, with 23% replying “certainly”, 30% “probably”, 27% “possibly”, 17% “probably not”, and 3% “certainly not”, to the question of whether the UFO problem deserves scientific study. Sturrock also asked in the same survey if the surveyee had witnessed any event which they could not have identified and which could have been related to the UFO phenomenon, with around 5% replying affirmatively.
In 1980, a survey of 1800 members of various amateur astronomer associations by Gert Herb and J. Allen Hynek of the Center for UFO Studies (CUFOS) found that 24% responded “yes” to the question, “Have you ever observed an object which resisted your most exhaustive efforts at identification?”
Studies, panels, and conferences
Project Sign, Project Grudge (US, 1947–1949)
The first official USAF investigations of UFOs were Project Sign (1947–1949) and its successor Project Grudge (1949). Several hundred sightings were examined, a majority of them having a mundane explanation. Some sightings were classified as credible but inexplicable, and in these cases the possibility of an advanced unknown aircraft could not be ruled out. The initial memos of the project took the UFO question seriously. After surveying 16 early reports, Lt. Col. George D. Garrett estimated that the sightings were not imaginary or exaggerations of natural phenomena. Lt. General Nathan F. Twining expressed the same estimate in a letter to Brig. General Schulgen, and urged a concerted investigation by the Air Force and other government agencies. Twining’s memo led to the formation of Project Sign at the end of 1947. In the summer of 1948, Sign’s first intelligence estimate (Estimate of the Situation) concluded that some UFO reports were extraterrestrial in origin. The rejection of the estimate by USAF Chief of Staff Gen. Hoyt Vandenberg led to the dissolution of Sign and the formation of Project Grudge.