Colorado project scientists attempted to evaluate the usefulness of the Prairie Network as an instrumented system for UFO searches. A list of UFO sightings dating back to 1965 that occurred within the network limits was presented to the supervisor of the field headquarters in Lincoln, Neb. He was requested to produce those plates which might conceivably have been able to photograph the objects which gave rise to the sightings. Information supplied to the supervisor was deliberately limited to case number, year, month, day, time, city, duration, direction, and location. Duration of the sighting was given in minutes. Direction in the sighting reports referred either to the direction in which the observer was looking, or the direction of motion of the object. Location was specified by the coordinates of an atlas. Presenting the information in this form avoided biases based on preconceptions and placed more emphasis on the immediate environs of the sighting point. The assumption that an UFO was in the immediate neighborhood of the sighting was made so as to combat any tendency to attribute sightings to distant objects, that is, to astronomical bodies.
A map was prepared for each case (see Fig. 2) and each film scanned for exceptionally bright objects and planes or satellites. Tracks of bright meteors were never seen because the films on which they appeared had been sent to Cambridge, but the azimuth, elevation, and trajectory of these meteors were available and correlated with the sighting report. Angular positions of bright objects were roughly determined by means of a template.
The following criteria-were applied to the reports and to the films:
- Not operating (NO): cameras do not operate before dusk or after dawn and they sometimes malfunction or run out of film.
- Meteor (M): a fireball with a known trajectory computed by its film tracks at several stations.
- Overcast (O): this applied to cases where two nearby stations were so overcast that no star images showed, and where there was little information on films from more distant stations.
- No information (NI) : this classification was used when the report failed to state the direction in which the observer was looking or the direction in which the object was moving, or both.
- No conclusion (NC) : the report information was so fragmentary that no correlation between the objects on the photograph and those reported, was possible, or the films gave no information which could confirm that an object was seen.
- Inconclusive identification (II) : if the photographic evidence showed the presence of a body which could have been responsible for the sighting with a fair degree of probability, the case was called inconclusively identified.
- Conclusive identification (CI): when description in the visual report was confirmed with a high degree of probability in all characteristics, the case was considered to be conclusively identified.
The following rules were adopted:
- All NI cases became NC
- No NO cases were labelled NC
- Some O cases were classified NC
Of 114 cases, two were identified as meteors, one conclusively and one inconclusively, four cases received conclusive and 14 inconclusive identifications. Of the remaining cases 80 were classified NC; and 14, NI or NI combined with NO and O.
The sighting identified conclusively as a meteor was made by a couple who were driving north on Highway 281, six miles north of Great Bend, Kans., at 2200 CST. They reported that they saw "... a flash or burst of fireworks above car, not unlike the usual Fourth of July fireworks, except that this was much larger and much higher. The fireworks or sparkles were varicolored and out of them emerged a disc-like object about the size of an ordinary wash tub. The object was as red as fire, but it appeared solid with a very definite, sharp edge ... and traveling at a tremendous speed. Its direction was north-northeast and in a straight line ... It did not require more than five seconds to reach a distance that made it invisible ..."
Two phrases in this statement needed clarification: "above us" and "its direction was north-northeast." The observer explained that "above us" meant "through the upper part of the windshield." He said that his (and his wife's) attention was called to the object by the flash of the burst, which they saw just to the west of north, and it vanished while still slightly west of north. He insisted that the object was traveling north-northwest, explaining the correction by saying that he often confused west with east. He was therefore certain that it could not have been on the NW to SE course determined from the photographic data, and that it was not a meteor because it was rising, not falling. Questioned as to the time, he said that 10:00 P.M. was approximate and that the duration of the sighting was short, probably less than the five seconds referred to.
Six stations of the Prairie Network photographed a meteor at about 10:10 P.M., determined that it passed over Republican City, Neb. at an altitude of some 50 km., and predicted that its point of impact was near Downs, Kans. Republican City lies a few degrees west of north from the sighting point at a distance of about 177 km., and Downs an equal number of degrees east of north at a distance of about 116 km. Assuming a mean distance of 145 km., the observer saw the meteor at an elevation of approximately 19°. The elevation of the top of a windshield of an American two-door sedan from the eye level of a man of average height is about 25° or less.
The observer's impression was that the object was rising. This would be expected if it were approaching him at a constant altitude. His strong feeling that it was on a northerly course, and therefore receding, is explained by recalling the very short time during which he saw it.
Considering the general agreement as to time, elevation and region of viewing, the probability is high that the object seen was the meteor photographed.
The second case was labeled inconclusive because, in spite of the paucity of information available about it, there was a relatively close agreement between the time of the sighting (0001 CST, 26 January 1967) and the time of a meteor recorded on three network stations (2341:51 CST, 25 January 1967). The discrepancy of only 18 minutes leads to a probable identification of the sighting as the meteor, but the identification cannot be made conclusive.
A striking example of the lack of correlation that can occur between a familiar object and the interpretation of a sighting is related in the case where a large, helmet-shaped, luminous body appeared overhead from behind a cliff. The observer was driving west. He reported that the object stayed nearly overhead for 45 min. until it disappeared behind a hill to the southwest at an altitude of about 40°.
Network photographs show the moon moving from 245° to 270° at a starting elevation of 85° dropping to 45° Stars and a plane also appeared on the film, but their positions did not tally with the report.
Neither the observer nor the Air Force interviewer mentioned that the moon was visible, but the conclusion appears to be inescapable that the object seen was the moon. A summary of the results of this study are presented in Table 2.
Bearing in mind that Prairie Network optics and geometry were designed to detect bright astronomical objects at high angular velocities, it is not surprising that 100% of the conclusive and 67% of the inconclusive identifications relate to astronomical objects. In fact, any future investigation utilizing the network should guard against a possible bias arising from its design features.
The network's identification of 18% of all sightings with a fair degree of probability, does not constitute as poor a performance as might be thought since 34% could not be recorded because of overcast and 43% were so deficient in information that, even if an object had been recorded by the film it would have been impossible to correlate it with the sighting.