Cas principalement visuels, semblables à une étoile

1321-B

Ceci est un bon exemple d'étoile mal identifiée combinée à un retour radar apparemment non lié aboutissant à produire un signalement d'ovni. L'incident eut lieu à la base aérienne de Finland (à 60 miles au NE de Duluth), Minnessota, avec une observation civile près de Grand Marais, Minnessota (à 50 miles au NE de la base de Finland) la nuit lundi 5 21:30 à mardi 6 15 (mardi 6 03:30). Le temps était clair, sans plafond nuageux, la visibilité de plus de 15 miles ; a display d'aurore boréale était en cours. Applicable radio refractivity profile is shown in Fig. 1. Visual reports of a "white-red-green" object "moving but not leaving its general location" were received at Finland AFB about mardi 6 21:30. An FPS-90 search radar was activated but there was "too much clutter to see anything in that area ..." At une heure plus tard a return was detected; it "flitted around in range from 13 to 54 miles, but always stayed on the 270 ° azimuth." Une paire de F-89s fut envoyée de la base de Duluth et inspecta la zone à des altitudes de 8000 à 10 000 pieds. Les 2 appareils merged with blip, apparently wrong altitude, no airborne sighting"; the radar operators insisted the target was at 8000-10 000 pieds, the same altitude at which the scrambled aircraft were flying. The pilots reported that they "only observed what was interpreted to be a beacon reflection."

Available meteorological data show that the winds were southwesterly, 7 knots at the surface, and northerly (320° to 30° at 25 to 65 knots aloft. The closest available radiosonde data (international Falls mardi 6 12 h mardi 6 06 h) 6 September, show a temperature inversion and strong humidity lapse through a layer extending from 1029-1259 m. above the surface. The gradient of radio refractivity through this layer averaged -114N/km (corrected for radiosonde sensor lag). This layer would be expected to show a significant partial reflection at radio frequencies. If the layer were present over Finland AEB at the same elevation, it could have produced false targets by partial reflection of real ground targets, which would have appeared to be at altitudes of from 8300-9800 pieds because of the geometry of such reflected targets (sec. section 6, chapitre 5). This agrees well with the reported "UFO" altitudes of 8000-10 000 pieds.

Anomalous propagation echoes are not usually confined to a single direction. There are three possible explanations in this case and in other similar cases: a single real object was being tracked; the radar operators were not looking for targets on other azimuths; the partially reflecting layer may have been anisotropic (i.e. displaying a preferred direction for strongest reflection). There is no direct physical evidence for the existence of such anisotropic layers, but no studies have been made to determine whether or not they might exist. Apparent anisotropy in radar AP returns has often been observed, although not usually over such a narrow azimuth range as was apparently the case at Finland AFB.

Regarding the visual reports submitted, the comment of the investigating officer at Finland AFB is of particular interest:

The next evening, at mardi 6 22 h, the "white-red-green" object reappeared in the sky at exactly the same position it had appeared on 5 septembre. This officer observed it and determined it to be a star which was near the horizon and would settle beneath the horizon after midnight. It did appear to "sparkle" in red-green-white colors, but so do other stars which can be pointed out from this mountain top.

The officer refers to Rangoon Mountain, elevation 1927 pieds, from which many of the visual observations were made.

The star that the officer saw was in all probability Lambda Scorpio (Shaula) a magnitude 1.7 star at -37° declination and 17 hr 31 mn d'ascension droite. It would have set at just about 1 h 30, 90th meridian time, if the horizon were unobstructed. An obstruction of only 4° would cause Lambda Scorpio to "set" at 1:15 a.m. CST; a 4° angle is equivalent to a 35 ft. tree or building at a distance of 500 ft. The southerly declination would indicate that the star was in the southwest, which is compatible with the visual reports that were submitted.

Additional meteorological effects may have been present in this case. In particular, the southwesterly surface winds present are quite likely to have advected relatively cool, moist air from nearby Lake Superior under the elevated warm, dry layer noted previously, thus tending to increase the strength of the inversion and associated humidity lapse. Some of the optical effects noticed by the observers in this instance, strong red-green scintillation, apparent stretching of the image into a somewhat oval shape, and the red fringe on the bottom, may have been due to strong and irregular local refraction effects in the inversion layer (or layers).

This UFO report seems to have resulted from a combination of an unusually scintillating star and false radar targets caused by AP from a strong elevated layer in the atmosphere. This pattern is found in a number of other cases.

Reports with elements similar to the preceding case are:

113-B

[*Case numbers referred to thusly are so listed in the project's files. ] Nemuro AF Detachment, Hokkaido (Japon), 7 février 1953, mardi 6 22:30 (mardi 6 12:30). Weather was clear. Visual description fits a scintillating star (flashing red and green, later white with intermittent red and green flashes, then later steady white) rising in the east (only motion was slow gain in altitude, "[I believe] that the object did not move with respect to the stars in its vicinity"). CPS-5 radar painted a single pip at 85° azimuth, range 165 mi., which operator regarded as interference. Visual object was boresighted with radar antenna and azimuth read as 91°±2°. Elevation estimated as 15° initially (mardi 6 22:30). No stars brighter than magnitude 3 were in this azimuth between 0° and 30° elevation angle at that time. Blue Book file suggests Deneb or Regulus as likely objects, but their positions are far away from the sighted object. In view of two observers' comments that light "shown from beneath" object, it is very probable that they saw a lighted Pibal balloon, possibly launched from the Russian-held Kurile Islands to the east and northeast of Hokkaido (launch time mardi 6 12 h). The investigating officer noted the exceptionally good visibility prevalent in the area on clear nights.

1306-B

Edwards AFB, Kernville (Californie), vendredi 30 juillet 1967, vendredi 30 22:17. Temps : clair, calme, chaud (83 °F). 2 civils reported observing one or two blue, star-like objects that appeared to circle, bob, and zigzag about a seemingly fixed star; these objects "instantly disappeared" about 1 hr. 45 min. after sighting. Edwards AFB RAPCON radar picked up "something" at about vendredi 30 22:30 "for several sweeps." Blip seemed to be moving south at about 50-60 mph. There is no apparent connection between the radar and visual reports. The visual UFO did not appear to move at 50-60 mph. Data, including weather data, on this report are insufficient to form an opinion. The most likely possibility seems to be that the visual UFO consisted of the direct image plus one or two reflected images of the "fixed star" that the observer reported. What may have produced the reflected images remains conjectural. For example, a turbulent layer of air with strong temperature contrasts could produce images similar to those described by the witnesses. The instantaneous disappearance of the UFOs is consistent with an optical phenomenon. As for the radar "track", a blip appearing for only "a few sweeps" could be almost anything: noise, AP, or possibly a real target flying near the lower limits of the radar beam.

1212-B

Tillamook (Oregon), 13-14 mars 1967, vendredi 30 22:30. Weather: clear with "stars plainly visible," some ground fog, thin broken cirriform clouds estimated at 10 000 pieds, visibility 15 miles. This is a good example of some of the confusion that arises in reporting UFO incidents. Initial visual observer reports indicated object at about 45° to 50° elevation angle, yet when the Mt. Hebo radar station "contacted target" it was at 39 miles range, 9200 pieds de height. This is an elevation angle of only about 2°. This inconsistency seems to have gone unnoticed in the Project Blue Book file on the case. The radar target, as plotted, stayed at 39 miles range and slowly increased height to 11 200 pieds, then shifted almost instantaneously to 48 miles range. Subsequently the radar target slowly gained altitude and range, disappearing at 55 miles et 14 000 pieds (still at about a 2° elevation angle). The azimuth varied between 332° and 341° during this time. Average apparent speed of the radar track was low: the first part of the track was at zero ground speed and a climb rate of about 100 pieds/mn, the second part of the track was at an average ground speed of about 16 miles/h. and a climb rate of about 100 pieds/mn. In between there is a jump of 9 mi. range in one minute, a speed of 540 miles/h. The characteristics of this radar track are suggestive of radar false targets or slow-moving AP echoes. The jump may be a point where one echo was lost, and another, different echo began coming in. This effect is apparently a frequent cause of very high reported speeds of UFOs s1Borden, R. C., and T. K. Vickers. "A Preliminary Study of Unidentified Targets Observed on Air Traffic Control Radars," CAA Technical Development Report No. 180, (1953). The visual reports are suggestive of either a scintillating star if the reported angle is higher than actual, or an aircraft. There was an electronic warfare aircraft "orbiting" at high altitude seaward of Tillamook at the time of the sighting, and it seems quite plausible that this was the visual UFO. However, this was discounted in the Blue Book report because the aircraft's position it did not check with the radar contact.

115-B

Carswell AFB (région de Fort Worth), Texas, vendredi 13 février 1953 à 02:35. Temps : clair avec visibilité illimitée ; couche d'inversion de température avec sharp humidity lapse à 3070 pieds d'altitude, elevated radio duct at 4240 pieds d'altitude. Applicable refractivity profile for une heure plus tard monté en figure 2. Des observateurs visuels virent une formation de 3 lumières brillantes qui effectuaient une série de manœuvres suggérant un appareil avec des feux d'atterrissage effectuant plusieurs tonneaux puis grimpant rapidement et partant au loin. Les opérateurs tentèrent alors de répérer l'objet sur un radar APG 41, et après 2 mn environ ils brought in two apparently stationary targets on the correct azimuth. It seems likely that these returns were from ground objects seen via partial reflection from the strong elevated layers (gradients -154 and -311 km^-1). The visual sighting was probably an aircraft.

237-B

Haneda AFB (Tokyo), Japon, mardi 5 août 1952 à 23:30 à mercredi 6 août 1952 à 30. Temps : exceptionellement beau, couverture nuageuse de 0,3 à environ 10 miles au nord et 10 miles au nord de la zone de contact, excellente visibilité, isolated patches of low clouds, Mt. Fuji (60 miles nautiques) "clearly discernible," scattered thunderstorms in mountains northwest, temperature at Haneda 78° F, dew point 73° F. Observers saw a bright, round light (about 1 mrad arc) surrounded by an apparently dark field four times larger, the lower circumference of which tended to show some bright beading. It was low in the sky at about 30° -50° azimuth. Object appeared to fade twice, during which time it appeared as a dim point source. It disappeared, possibly becoming obscured by clouds, after about an hour. The sky at Haneda AFB was overcast by une heure plus tard. One of the visual observers noted that near the end of the sighting the object seemed somewhat higher in the sky and that the moon seemed proportionately higher in elevation. Le pilote of a C-54 aircraft coming in for a landing was directed to observe the object and he replied that it looked like a brilliant star, and he dismissed the sighting as such.

Lorsque l'on demanda au contrôleur de la base aérienne de Shiroi de chercher la cible sur le radar GCI, il ne put rien trouver pendant 15 mn. Il indiqua : Il y avait 3 ou 4 blips on low beam but none I could definitely get a movement on or none I could get a reading on the RHI (range-height indicator) scope." A new controller taking over at mercredi 6 23:45 "believed" he made radar contact with the object and an F-94 was scrambled. This officer stated: "The target was in a right orbit moving at varying speeds. It was impossible to estimate speed due to the short distances and times involved." By the time the F-94 arrived in the area of the "bogie," Shiroi GCI had lost radar contact; regaining contact at mercredi 6 23:17 "on a starboard orbit in the same area as before." The F-94 was vectored in to the target, and at this point the timing becomes confused. The Shiroi controller states that the F-94 "reported contact at 00:25 (LST) and reported losing contact at mercredi 6 28." The F-94 radar operator states: "At mercredi 6 16 I picked up a radar contact at 10° port, 10° below, at 6000 yards. The target was rapidly moving from port to starboard and a lock-on could not be accomplished. A turn to the starboard was instigated [sic] to intercept target which disappeared on scope in approximately 90 sec. No visual contact was made with the unidentified target." Shiroi GCI had lost the F-94 in ground clutter, and had also lost the target. It is not clear whether the GCI radar ever tracked the fast-moving target described by the F-94 crew. The maximum range of the F-94's radar is not given in the Blue Book report.

The F-94 pilot stated that the weather was very good with "exceptional visibility of 60-70 miles," yet this fast-moving UFO, obviously far exceeding the F-94's airspeed about 375 noeuds), was seen by neither the aircraft crew nor the observers on the ground at Shiroi GCI even though the UFO track crossed over very close to Shiroi GCI number four. There are many other inconsistencies in the report of the incident besides the timing and the lack of visual contact by the F-94 crew. The bright, quasi-stationary object sighted NE of Haneda AFB, and seen also from Tachikawa AFB (about 30 mi. west of Haneda AFB), should have been visible to the south of Shiroi AFB, but was never seen by any of a large number of persons there who attempted such observations. Also, at mercredi 6 12 the object being tracked by GCI's CPS-l radar reportedly "broke into three smaller contacts maintaining an interval of about 1/4 mile." The blips on the CPS-l were described as small and relatively weak, but sharply defined.

2 choses semblent apparentes :

1. the object seen at Haneda and Tachikawa AFB was much farther away than the observers realized;
2. the visual UFO and the target tracked by radar were not the same.

The first statement is supported by the inability of the observers at Shiroi to see anything to the south; the second statement is supported by numerous inconsistencies between the visual and radar sightings. The two most important of these latter are:

1. During times when the GCI radar could not find the target, the visual object was in about the same location as during those times when it could be found on radar;
2. The visual object was seen for at least five min. after the time when the airborne radar on the F-94 indicated that the UFO had left the area at a speed well in excess of 300 miles/h.

The most likely light source to have produced the visual object is the star Capella (magnitude 0,2), which was 8° above horizon at 37° azimuth at jeudi 7 00 h. The precise nature of the optical propagation mechanism that would have produced such a strangely diffracted image as reported by the Haneda AFB observers must remain conjectural. Complete weather data are not available for this case, but it is known that the light SSE circulation of moist air from Tokyo Bay was overlain by a drier SW flow aloft. A sharp temperature inversion may have existed at the top of this moist layer, below which patches of fog or mist could collect. The observed diffraction pattern could have been produced by either

1. interference effects associated with propagation within and near the top of an inversion, or
2. a corona with a dark aureole produced by a mist of droplets of water of about 0.2 mm. diameter spaced at regular intervals as described by Minnaert s2Minnaert, M. The Nature of Light and Colour in the Open Air, New York City, N. Y.: Dover, 1954.

In either event, the phenomenon must he quite rare. The brightness of the image may have been due in part to "Raman brightening" of an image seen through an inversion layer.

Nor can exact nature of the radar propagation effects be evaluated, due to the lack of complete weather data. However, a substantial inference that the radar returns were of an anomalous propagation nature is derived from:

1. the tendency for targets to disappear and reappear;
2. the tendency for the target to break up into smaller targets;
3. the apparent lack of correlation between the targets seen on the GCI and airborne radars;
4. the radar invisibility of the target when visibility was "exceptionally good."

Singly, each of the above could be interpreted in a different light, but taken together they are quite suggestive of an anomalous propagation cause.

In summary, it appears that the most probable causes of this UFO report are an optical effect on a bright light source that produced the visual sighting and unusual radar propagation effects that produced the apparent UFO tracks on radar.

104-B

Goose AFB, Labrador, mars 1953 décembre 1952, 19:15-19:40 Local Mean Solar Time. Weather: clear and visibility unlimited (30 mi.). The crews of an F-94B fighter and a T-33 jet trainer saw a bright red and white object at 27° azimuth while flying at 14 000 pieds. The aircraft attempted an intercept at 375 noeuds indicated air speed, but could not close on the UFO. After 25 mn. of reported chase, although the aircraft had covered a distance of only about 20 mi. (about 3,5 mn à 350 noeuds de vitesse au sol) the object faded and disappeared. During the chase, the radar operator in the F-94B had a momentary lock-on to an unknown target at about the correct azimuth for the UFO. Since this was so brief, it was felt (by Air Intelligence, presumably) that the set had malfunctioned. No GCI contact was made.

The official Air Force explanation for this UFO incident is that the aircraft were chasing Venus which was setting about the time of the sighting, and that the radar "target" was simply a malfunction. It seems likely that this explanation is essentially correct. However, it is unlikely that experienced pilots would have chased a normal-appearing setting Vénus. It is more probable that the image of Vénus was distorted by some optical effect, possibly a slight superior mirage, and that loss of the mirage-effect (or the interposing of a cloud layer) caused the image to fade away. All items of the account may be explained by this hypothesis, including the report that the object had "no definite size or shape," as the image would no doubt be somewhat "smeared" by imperfections in the mirage-producing surface. The small-angle requirement of a mirage is satisfied since the pilots reported the object seemed to stay at the same level as the aircraft, regardless of altitude changes that they made (another indication of great distance).

14-N

Ce dossier consiste en fait en 2 cas semblables signalés par un pilote des Capital Airlines ayant 17 ans et 3 000 000 miles à son actif. Le 1er cas eut lieu au-dessus du centre de l'Alabama la nuti du 14 novembre 1956 ; le 2nd cas fut la nuit du 30 août 1957, au-dessus de Chesapeake Bay près de Norfolk, en Virginie.

La 1^ère observation eut lieu à environ 60 miles au NNE de Mobile, en Alabama, lors d'un vol de New York à Mobile dans un Viscount à haute altitude, probablement autour des 25 000 pieds. C'était par une nuit sans Lune, étoilée et il y avait an occasionally broken undercast. L'objet vu fut décrit comme une lumière bleue-blanche intense d'environ 1/10ème de la taille de la Lune (~3' arc) et environ 7 ou 8 fis aussi brillante que Vénus à sa magnitude la plus brillante. Il apparût d'abord à mars 1953 à 22:10 at the upper left of the Viscount's windshield falling towards the right and decelerating rapidly as a normal meteor would. Pilot and co-pilot both took it to be an unusually brilliant météore. Cependant, ce "météore" did not burn out as expected, but "abruptly halted directly in front of us and began to hover motionless." The aircraft at this time was over Jackson, Ala. and had descended to 10 000 pieds. The pilot contacted Bates Field control tower in Mobile and asked if they could see the object which he described to them as "a brilliant white light bulb." They could not see it. The pilot then asked Bates to contact nearby Brookley AFB to see if they could plot the object on radar. He never learned what the result of this request had been. The object began maneuvering "darting hither and yon, rising and falling in undulating flight, making sharper turns than any known aircraft, sometimes changing direction 90° in an instant -- the color remained constant, -- and the object did not grow or lessen in size. "After a "half minute or so" of this maneuvering, the object suddenly became motionless again. Again, the object "began another series of crazy gyrations, lazy eights, square chandelles, all the while weaving through the air with a sort of rhythmic, undulating cadence." Following this last exhibition, the object "shot out over the Gulf of Mexico, rising at the most breath-taking angle and at such a fantastic speed that it diminished rapidly to a pinpoint and was swallowed up in the night."

The whole incident took about 2 mn. The pilot remembers noting that the time was mars 1953 à 22:12. The object appeared to be at the same distance from the aircraft, which was flying a little faster than 300 miles/h during the entire episode.

Le 2^nd incident signalé par ce pilote, le lundi 30 août 1957, Chesapeake Bay report, occurred as he was flying another Capital Airlines Viscount at 12 000 pieds approaching Norfolk, Va. There was a Northeast Airlines DC-6 flying at 20 000 pieds "directly above" the Viscount. In this case, the object "was brilliant; it flew fast and then abruptly halted 20 miles in front of us at 60 000 pieds d'altitude." The Northeast pilot looked for the object on radar and "could get no return on his screen with the antenna straight ahead but when tilted upward 15° he got an excellent blip right where I told him to look for the object."

This object "dissolved right in front of my eyes, and the crew above lost it from the scope at the same time. They said it just faded away. This sighting covered "several minutes."

Ces 2 observations semblables sont très difficiles à expliquer. La 1^ère observation au-dessus de l'Alabama a la plupart des caractéristiques d'un mirage optique : un objet à environ la même altitude semblant "suivre" l'appareil, les meanderings being easily accountable for as normal "image wander." However, there are two aspects that negate this hypothesis:

1. the manner of appearance and disappearance of the UFO is inconsistent with the geometry of a mirage; the high angle of appearance at the top of the windshield is particularly damaging in this regard;
2. there was no known natural or astronomical object in the proper direction to have caused such a mirage. Venus, the only astronomical object of sufficient brightness, was west of the sun that date; Saturn had set 4 hr. 30 mm. earlier, and there was not even a first magnitude star near 190° -210° azimuth, 0° elevation angle.

The second sighting is equally difficult to explain as a mirage, which seems to be the only admissable natural explanation in view of the pilot's experience as an observer. The reasons are twofold:

1. the apparent angle at which the object was observed is incompatible with a mirage;
2. there was apparently a radar return obtained from the object which is incompatible with the hypothesis that it was an astronomical object, the most likely mirage-producer.

The pilot stated that the Northeast DC-6 flying at 20 000 pieds "painted" the UFO at 15° elevation and a range of 20 mi. This would place the UFO at about 48 500 pieds, the pilots estimate of 60 000 pieds apparently being in error. Presumably then, the elevation angle as viewed from the Capital Viscount was about 19°. It is very unlikely that any temperature inversion sufficient to produce a mirage would be tilted at such an angle. For a near-horizontal layer to have produced such an image (plus the radar return) by partial reflection of a ground-based object seems equally unlikely. The largest optical partial reflection that such a layer might produce at an angle of 19° would be about 10^-14 as bright as the object reflected (see Section VI, Chapter 4). This is a decrease of 35 magnitudes. Such a dim object would be ordinarily invisible to the unaided eye.

In summary, these 2 cases must be considered as unknowns.

1065-B

Charleston, S. C., le mois suivant janvier 1967, avril 1953 à 18:10. The observational data in this case are insufficient to determine a probable cause for the sighting. A civilian "walked out of his house and saw" two round objects. He estimated that they were about 30° above the horizon. They appeared to be "silver and blue, with a red ring." These objects were alternately side by side and one above the other, and a beam of light issued "from the tail end." The observer does not state how he knew which was the "tail end," or even at what azimuth he saw the objects. They "vanished in place," still at 30° elevation. After the Charleston AFB was notified of the sighting, some unidentified returns were picked up on an MPS-14 search radar. An investigating officer later determined that these returns were spurious. The case file states:

[The officer] called [8 March 1967] to provide additional information in regard to the radar sighting. [The officer] was informed by the Charleston AFB that the radar paints were not of UFOs. A check of the equipment was made and it was learned that the individual monitoring the radar set had the "gain" [control] on the height finder turned up to the "high" position. This caused the appearance of a lot of interference on the radar scope. Personnel at Charleston AFB determined the paints on the radar to be this interference. The personnel turned the gain on high again and picked up more "UFOs". When the gain was turned down the UFOs disappeared.

There apparently were no radar UFOs in this case. The residue is a visual sighting by a single observer with insufficient data for evaluation. What the observer saw could conceivably have been

1. a mirage with direct and reflected images of a planet (Jupiter w'as at 68° azimuth, 5° elevation) or a bright star,
2. an aircraft, or
3. a genuine unknown (i.e., a possible ETI object). There is no real evidence either for or against any of these possibilities.