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The following is a summary of weather conditions surrounding UFO visual and radar sightings near .... [AFB A] between 7:30 P.M. and midnight on .... [the date of the first sighting].
Pacifique Sud, Automne 1967
Enquêteurs : Levine, Low et autres
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Les événements commençèrent avec une observation visuelle vers 20 h 00 d'un objet stationnaire avec des lumières colorées au-dessus de l'océan. On demanda à des radars de suivi de missiles de rechercher l'objet ; ils repérèrent immédiatement de nombreuses cibles non identifiées, la plupart d'entre elles en mouvement, et les suivirent. La plupart des cibles en mouvement permirent le verrouillage radar. Elles se déplaçaient à des vitesses allant jusqu'à 80 noeuds, et retournaient parfois des échos très forts. Plusieurs observations visuelles supplémentaires furent signalées. La plupart des observations furent faites au-dessus de l'océan, mais certaines cibles apparurent à l'Est et au Nord, au-dessus des terres. Les cibles radar étaient toujours observées lorsque l'équipement fut fermé vers 2 h 30. Encore aucun appareil n'était connu être dans la zone, et 3 vols de chasseurs envoyés pour investiguer ne trouvèrent rien d'inhabituel.
Une inversion de température inhabituellement forte offrit des conditions favorables aux effets de mirage visuels comme radar. Des mirages de navires en-dessous de l'horizon normal semble expliquer de manière adéquate les objets stationnaires ou lents. Les cibles radar plus élevées et plus rapides étaient cohérentes avec des oiseaux, que les opérateurs de suivi radar n'avaient pas eu l'occasion d'observer auparavant. Des observations radar semblables furent signalées lors de 2 jours suivants.
Le Projet Blue Book avait notifié le projet du Colorado de cette observation visuelle et radar intéressante à l'AFB A. Il fut également signalé que, lors d'un test 3 nuits après l'observation, il avait été établi que les radars à la base avaient pu à nouveau observer des "bogies" semblables à ceux observés la nuit de l'observation d'origine. Des enquêteurs du projet et d'autres visitèrent le site en 2 dates différentes. Lors du dernier jour, étaient présents : R. T. H. Collis, Roy Blackmer et Carl Herold de l'Institut de Recherche de Stanford ; Marx Brook de l'Institut de Mining et Technologie du Nouveau Mexique ; Roger Lhermitte de l'Administration des Services de Science Environmentale ; et Low et Levine du projet du Colorado. Lors du 1er rendez-vous Low et e Dr. Robert Nathan du Jet Propulsion Laboratory avaient visité l'AFB A.
Les observations de l'AFB A furent exceptionnels en raison des hautes qualifications professionnelles des observateurs. 2 étaient des responsables du Site d'Essais Western, chacun ayant 17 ans d'expérience comme aviateur naval. L'un d'entre eux avait 10000 h comme contrôleur d'interception aérienne et d'approche final ; l'autre avait également été contrôleur d'interception aérienne. Un 3ème, qui était Officier de Contrôle Aérien du Site la nuit de la 1ère observation avait 11 ans d'expérience de systèmes électroniques au sol et aériens embarqués. 6 autres étaient des opérateurs radar employés par des contractants privés sur la base, dont tous avaient eu une expérience étendue en opération radar. Ils affichaient une compréhension impressionnante des systèmes radar sophistiqués qu'ils opéraient et une bonne compréhension des principes d'ingéniérie radar. 1 autre témoin était de la force de sécurité, sans formation technique étendue.
Les radars suivants étaient impliqués dans les observations.
20 h 00 à 20 h 45 : Pendant 1/2 h un responsable du site de missiles observa depuis chez lui un objet à l'azimut 290 °. Il appela un autre responsable, également chez lui à 3 miles au sud, qui confirma l'observation à l'azimut approximatif de 280 ° et une altitude de 10 ° à 15 °. Le 2nd observateur signala que l'objet, vu à travers des jumelles 7 X 50, semblait avoir la taille d'un grand thumbtack, de forme elliptique et ayant une lumière rouge et verte séparées d'une distance de l'ordre de l'envergure d'un avion. Mais l'objet était stationnaire, et flou comme un sommet en rotation.
20 h 45 : L'observateur n° 2 appela les Opérations de Contrôle du Site (située à une altitude de 900 à 1100 pieds). L'officier de contrôle du site confirma l'observation visuelle. Pour lui elle semblait avoir des couleurs blanche, rouge et verte ou bleue qui ne variaient pas. Elles avaient l'air de lumières de fonctionnement d'un objet stationnaire. Il donna son orientation comme étant 290 °, une portée de plusieurs miles, une altitude approximative de 10000 pieds et suggéra que l'objet avair l'air d'un hélicoptère.
20h 45 : Le radar FPS-16 en mode recherche verrouilal sur 2 cibles fortes, une se déplaçant autour et une stationnaire. La cible stationnaire apparut dans la direction générale de l'observation visuelle, mais la position optique ne fut pas déterminée avec suffisamment de précision pour établir qu'il s'agissait d'une observation optique-visuelle simultanée. L'interpretation d'origine fut un hélicoptère, avec un autre l'assistant.
21 h 00 : L'officier de contrôle du site vérifia avec plusieurs autres bases aériennes le traffic aérien posssible dans la zone de la l'AFB A. Toutes répondirent par la négative.
21 h 00 : En utilisant son FPS-16 en mode de verrouillage automatique, la base D signala 2 cibles fortes dirigées vers l'AFB A. En raison du rayon mince du radar les cibles furent présumée être en ligne.
21 h 00 : Le radar TPQ-18 à l'AFB A fut mis en opération, et vit de nombreuses cibles. Une, à une portée de 8 miles nautiques 4000 pieds d'altitude, 290 ° d'azimut et 4,6 ° d'élévation procédait au sud à base vitesse. Une cible forte approchait et arriva directement en survol. A un moment, le TPQ-18 vit 4 cibles. La base D en vit jusqu'à 8. L'AFB A et la base D n'établirent pas qu'elles examinaient les mêmes cibles.
23 h 10 : Le Commandement de la Défense Aérienne envoie le 1er des 3 vols de chasseurs pour examiner la situation. La bande des conversations avec les sites radar et d'autres bases démontrent une confusion considérable à ce moment.
Les chasseurs furent handed off to AFB A Range Control by the FAA at a nearby city and controlled locally. Range Control tried to vector the fighters in on the bogies, but found it impossible to do so very systematically. By the time the second flight came in, the controllers were so busy with the aircraft that they no longer observed any unidentified targets. They did observe a moderate amount of clutter in the west and southwest quadrant. None of the fighter pilots saw anything. One pilot observed something repeatedly on his infrared detector, but only at distance. As soon as he would close in, the object would disappear. Another aircraft did "lock-on" to a target which was found to be a ship.
The weather officer reported that there was an inversion layer at 1800-2200 pieds (The unidentified targets generally were reported to be above the inversion). All observers indicated that the night was exceedingly clear. The project's consulting meteorologist reports:
Figure 4: Vandenberg AFB Weather Situation The following is a summary of weather conditions surrounding UFO visual and radar sightings near .... [AFB A] between 7:30 P.M. and midnight on .... [the date of the first sighting].
Sources de données
Données radiosonde et de vent depuis --
.... [AFB A, island A, city A]
Observations météo de surface autour des moments des observations depuis --
.... [villes B, C, D, E ; AFB A, B, C ; base D]
Situation météo générale
In a weather sequence which moved a trough line and a low pressure center southeastward from northwestern Utah to northwest Texas.... [the day prior to the first sighting], a dome of high pressure formed over the Great Basin and a surge of warm air moved from northeast to southwest.... Most of the surge of warm air moved southwestward from the southern part of the .....Valley between midnight.... [the day before the sighting] and 15 h 00. ...[the day of the sighting]. Weather stations near the coast from ...[ville B] to ...[ville D] all showed abnormally warm temperatures at a time of day when ordinarily a sea breeze would have created a cooling influence.
THE OVER-OCEAN FLOW OF WARM DRY AIR
Using surface wind data from various coastal stations it is possible to reconstruct an approximate pattern of the forward edge of the warm, dry air which moved out over the ocean from a general northeasterly direction. For most stations, fairly strong northeasterly winds were maintained through 11 h 00 (voir Fig. 4) with northeast winds continuing until 3:00 P.M. at the surface at ....[AFB B].
The upper wind flow from 1000' to 7000' was still from an easterly component at ....[island A] shortly after 3:00 P.M. By 4:00 P.M. air was still moving from an easterly component between 3000' and 10,000' over....[AFB A]. Near the surface westerly winds were beginning to move the warm air back toward the east and southeast. This air had been cooled and some moisture had been added during its stay over the ocean.
Figure 5: Time/Temp Charts - Vandenberg AFB Weather Situation (Charts of Warm Air Abnormalities) During most of the afternoon hours the modified air moved from the ocean back over the coastal area. Some of the strongest evidence of the bulge of warm air over the ocean is indicated by the warm, dry air that moved over ....[city D] between the hours of noon and 17 h 00. With surface wind directions from 240° through 300°, temperatures held above 80° with maximum of 90°. A portion of the heating of this air would have been caused by dynamic heating as it it moved downslope from the .... mountains.
The abnormality of the warm air is indicated in Figures 5 and 6 by the approximate difference in air temperatures entre 6 h 00 et 8 h 00. The blue profile of normal.... temperature [the date of the first sighting] was made up from long term average maximum and minimum temperatures and an assumed sea breeze influence. The red shaded area indicates the approximate abnormality of warm temperatures on this day as warm, dry air moved from land toward the ocean as compared with typical weather for.... [the date of the first sighting]. The hatched area shows the abnormality remaining after the air had been modified by its path over water.
REFRACTION RESPONSE TO WARM, DRY AIR
When warm, dry air is forced to move from a land mass out over cooler water it creates a narrow boundary of mixing as moisture is picked up from the ocean developing small turbulent eddies of cooler, more moist air near the ocean surface. This is accompanied by very rapid fluctuations of refractive index. At the upper edge of the bulge of warm, dry air there would be another more difuse boundary where some- what less sharp differences in both temperature and moisture would be present. However, there would be corresponding fluctuations in refractive index.
Figure 6: Time/Temp Charts - Vandenberg AFB Weather Situation (Charts of Warm Air Abnormalities, Pt Mugu & amp; Long Beach) The Glossary of Meteorology defines a mirage as a refraction phenomenon wherein an image of some object is made to appear displaced from its true position...The abnormal refraction response for mirages is invariably associated with abnormal temperature distribution that yield abnormal spatial variations in the refractive index. Complex temperature distributions produce correspondingly complex mirages.
The layer of warm, dry air above cooler water from the ocean would have been particularly conducive to anomalous propagation of any radar unit scanning the atmosphere at low angles. A somewhat less important segment of the air mass capable of producing anomalous propagation on the radar would have been the upper boundary of the bulge of warm dry air. The following is quoted from Battan's book on RADAR METEOROLOGY under the heading of Meteorological Conditions Associated with Non-standard Refraction. "There are various ways that the index of refraction can be modified to give rise to anomalous propagation... When warm, dry air moves over cooler bodies of water, the air is cooled in the lowest layers, while at the same time mois- ture is added. In this way strong ducts are produced. These conditions are frequently found over the Mediterranean Sea as air blows off the African continent. Extreme anomalous propagation has been experienced in this region. For example, there have been days when centimeter radar sets have 'seen' ground targets at ranges of 400-500 miles, even though the horizon was at perhaps 20 miles. In conformance with meteorological terminology, superrefraction brought about by the movement of warm, dry air over a cool, moist surface may be called 'advective superrefraction.' By the nature of the processes involved, it can be seen that such conditions can occur during either the day or the night and last for long periods of time. The duration would depend on the persistency of the glow patterns producing the advection."
Figure 7: Wind/Temp Profiles - Vandenberg AFB Weather Situation< br > (Wind & amp; Temperature Profiles) Figure 7 contains the wind and temperature profiles for ....[island A] and ....[AFB A] beginning with release times of 15 h 15 and 16 h 08 (PST) respectively on ....[the date of the first sighting]. At ....[AFB A] (shown by the solid lines of temperature, dew point, wind direction and velocity) dry air prevailed for all levels above the surface at : 16 h 00. (For the lowest point on the profile, surface temperatures reported at 19 h 30 have been substituted). The vertical sounding of temperature, dew point, wind velocity and direction for ....[island A] are indicated by the dashed lines in Figure 7. Temperatures even warmer than over ....[AFB A] were reported in the ascent above ....[island A]. For emphasis, the area shaded in red indicates how much warmer the temperatures were over ....[island A] than at ....[AFB A] during the mid-afternoon hours. Ocean water temperatures between 58° and 59° were being reported, which is considerably cooler than the warm, dry air having temperature in the 80's as it moved from land to over the water.
CONCLUSION
It is the author's opinion that the surge of very warm, dry air may have caused a mirage and visual observations could have been correspondingly distorted in the vicinity of ....[AFB A] between 7:30 P.M. and 8:30 P.M. It is more certain that the air mass conditions prevailing over the water continuing through at least midnight in an arc from south of ....[AFB A] swinging eastward to the coastline could have produced anomalous propagation echoes on radar. Visibility observations were generally 12 miles or greater at all stations and no clouds were reported by the observer at ....[AFB A] between 19 h 00 et minuit. ....[base D] reported a few stratus clouds offshore in the Remarks Column beginning at 19 h 00 continuing through 23 h 00.
3 jours après la 1ère observation, sous des conditions météo similaires au 1er jour mais avec plus de vent, plus de nuages et des températures plus basses, le radar FPS-16 à....[AFB A] fut opéré pour déterminer si des cibles semblables pouvaient être vues à nouveau. Des cibles ayant les mêmes caractéristiques générales furent acquises, mais elle ne furent pas aussi fortes que les premières observations. 2 autres opérateurs, travaillant non officiellement avec un radar différent, indiquèrent qui observaient some of the same sort of stuff.
On the night of the investigators' second visit, similar targets were acquired on the FPS-16 and TPQ-18 radars. The radar experts among those present (Blackmer, Brook, Collis, Herold, Lhermitte) immediately requested that printouts be obtained giving information on signal strength. This information could not be compared with earlier sightings because the operators had not taken steps to print out the data from the other observations.
The AFB A series of sightings is remarkable for two reasons; first, because of the extraordinarily high qualifications of the observers, and second, because of the availability of hard instrument data. No other UFO case in the records of the Colorado project contains so many numbers, representing such quantIties as range, azimuth, elevation, and velocity. Information from which signal strengths could have been computed also would have been available had the operators thought to print it out, but they did not. To relate signal strengths and ranges for these events, it was necessary to go back to the tape of the conversations and find the reports of signal strengths, which, when assigned precise times (fortunately, the tape contained good timing references), could be compared with the printouts of range, which also included timing references. Information on the visual sightings was, except for the high credibility of the observers, comparable to that in other reports of UFO sightings in the Colorado files: i.e., no reliably measured quantitative values were available from such sightings.
The detailed weather study by Loren Crow was not available at the time of the second trip to AFB A, so that it was not known at that time that the atmospheric conditions were in fact quite unusual. Fig. 7 of the Crow report indicates that at AFB A, although return air flow at the surface was well established by the late afternoon of the original sighting, the flow at 2000 pieds was still from the northeast, so that a thin sheet of warm, dry air lay over the cool, moist air. This sheet of air extended southward almost to the island, where there was return flow from the surface to 3000 pieds, but easterly flow persisted from 3000-10000 pieds. There were strong gradients of moisture and temperature at both stations. Crow has pointed out that the temperature and moisture contrasts probably were even greater than those shown, because the surface measurements were not made at the surface, but at some distance above it. Altogether the weather report indicates that conditions were very favorable indeed for optical mirage and scintillation and for anomalous radar propagation.
It should be noted that the incident that set off the entire sequence of events was an optical sighting at 20 h 00. It appears highly probable that the observer saw the running lights of a ship below the normal horizon, but made visible as a result of mirage. The conditions for such a mirage were present, but it must be pointed out that both the first two witnesses insisted emphatically that the object appeared at an elevation of about 10°. That is too high for a mirage of a ship's lights below the horizon. Hence, either their reports of the elevation angle were incorrect, or some other explanation must be found. However, even experienced observers tend to overestimate elevation angles.
A further fact is of interest, and that is that, in the Operations Control Center on the date of the second visit to AFB A, one of the operators of a search radar declared that he never saw any ships, that the shipping lanes were too far off the coast for ships to be seen by radar from that location, although the antenna was at an altitude of approximately 1,000 ft. He thereupon switched to his most distant range (80 mi.) and immediately a sprinkling of blips appeared at extreme range. They turned out to be ships, their identity confirmed by their slow speed. Since there is no reason to suppose, from a quick study of weather conditions that night, that anomalous propagation had anything to do with the observation of ships, it must be concluded that they could be seen any time. The only reasonable explanation of the operator's statement that he never saw ships on the scope is that he had never looked for them. Both the original witnesses indicated that large ships never were seen visually from the coast, and that is undoubtedly correct, because they would be below the horizon. Computations show, however, that, under mirage conditions, the running lights of ships would be visible at the 80 mi. range the radars had indicated.
Some of the visual sightings obviously were not of ships. However, they were impossible to evaluate on the basis of the limited and subjective descriptions given. In this connection, it is significant to note the importance of quantitative instrument observations or records in such investigations. The visual objects could not be evaluated with much confidence, for lack of definitive evidence; but abundant quantitative radar records made it possible to identify most of the radar targets beyond serious doubt.
The behavior and characteristics of the unidentified radar targets appeared to be consistent with the hypothesis that most of them were birds. Individual birds would produce signal strengths consistent with those observed. (The targets observed the night of the second visit to AFB A, according to calculations made by Dr. Lhermitte, yielded a radar cross section of approximately 10 cm.2). The velocities and coherent tracks of the targets also suggested consistency with the bird hypothesis.
In view of the remarkable inversion conditions on the date of the original sighting, it is highly probable that some of the radar targets were effects of anomalous propagation (radar mirages). Temperature and moisture gradients were quite sufficient to produce echoes from atmospheric discontinuities.
At first, even the radar experts were puzzled by the radar data, because the remarkably strong echo signals returned by some of the targets suggested much larger objects than birds. Their confusion was resolved when it became apparent from comparisons of range data and concurrent signal strengths that the very strong signals were always associated with targets at close range. A radar echo declines in strength proportionally to the fourth power of the distance of the target from the antenna, so that even a small target at unusually short range can produce a very strong signal. Also, the pulse power of the tracking radars was much greater than that of the more familiar search radars, and they were normally used to track relatively distant rockets. Consequently, their use in the unaccustomed search mode drew attention to the deceptively strong signals from very near targets.
No attempt had been made during the sightings to associate ranges and signal strengths. Had someone asked, "When you get an 80-dB signal, what range do you read?" the evening probably would have ended differently. Future radar operating procedures might very well provide that, when unidentified targets are causing concern, ranges and signal strengths be correlated. Apparently no formal procedure existed at the time of the sightings for use in identifying unusual radar targets such as insects, sidelobe echoes, anomalous echoes from object on the ground, etc. In the absence of such a procedure, the operators involved in this case handled the situation reasonably.
Certains commentaires dans une lettre de M. Collis sont particulièrement pertinents :
Je pense que l'.... incident could be a landmark case in the whole area of UFO studies. It combines so many factors. Firstly, the incident involved a whole complex of associated events which were reported by the most respectable observers. It combined multiple radar and multiple optical sightings. It occurred very recently and a substantial amount of recorded, data is available-- i.e., the TPQ 18 radar records and the meteorological data. At least in part, the radar echo phenomena were repeatable and were observed by design on subsequent occasions. It was sufficiently strange to cause interceptor aircraft to be sent off to investigate it in the heat of the moment, and also to cause the local and visiting experts considerable perplexity even in the cool light of day. We thus have a wonderful opportunity not only to study the physical nature of the incident but also to study the psychological implications of such incidents.
It would seem that most of the inexplicability of the events in this case (and possibly in many others) arises not from the facts themselves, (i.e., the specific sightings, etc., at any given instant) but in the interpretation made and significance attached to them when they were considered in inappropriate juxtapositions. The way in which this was done at the time under operational pressures and even subsequently provided, in my opinion, a most important object lesson.
It does indeed ! La leçon est que la "vague" aurait pu être évitée si les opérateurs radar avaient été au courant des types de cibles qui pourraient repérer en mode de recherche, en particulièrement lors de conditions atmosphériques anormales. Il est peu probable qu'une telle "vague" ait lieu à nouveau à l'AFB A dans de telles circonstances ; mais cela peut arriver ailleurs à moins que cette expérience ne soit communiquée via les procédures d'opération appropriées ou d'une autre manière, aux autres opérateurs de radar de suivi puissants.
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