Condon Report: 1321-B. This is a good example of a misidentified star combined with an apparently uncorrelated radar return causing an UFO report to be generated. The incident took place at Finland Air Force Base (60 mi. NE of Duluth), Minn., with a civilian sighting near Grand Marais, Minn., (50 mi. NE of Finland AFB) on the night of 5-6 September 1966, between 2130 and 0015 LST (0330-0615 GMT). The weather was clear, ceiling unlimited, visibility more than 15 mi.; a display of Aurora Borealis was in progress. 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 2130 LST. An FPS-90 search radar was activated but there was "too much clutter to see anything in that area ..." At 2200 LST a return was detected; it "flitted around in range from 13 to 54 mi.., but always stayed on the 270° azimuth." A pair of F-89s was scrambled from Duluth AFB and searched the area at altitudes of 8,000-10,000 ft. The two aircraft "merged with blip, apparently wrong altitude, no airborne sighting"; the radar operators insisted the target was at 8,000-10,000 ft., 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 1200 GMT 0600 LST) 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 8,300-9,800 feet because of the geometry of such reflected targets (sec. Section VI, Chapter 5). This agrees well with the reported "UFO" altitudes of 8,000-10,000 ft.

Figure 1: International Falls

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 2200 hours, the "white-red-green" object reappeared in the sky at exactly the same position it had appeared on 5 September. 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 1,927 ft., 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 min. right ascension. It would have set at just about 1:30 a.m. 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.

Google map of this location.