5) The photographs confirmed this reconstruction of a complicated series of events. The pictures obtained by the gun camera displayed a round, indistinct blur. Analysis showed that the size of the object was that of a twenty-foot sphere—a balloon—photographed from a distance of 30,000 feet.
“Ghosts” and “Angels” on Radar
Every experienced radar man has observed blips on his scope that he cannot account for[VIII-4], but he recognizes many characteristics of these “ghosts” or “angels.” They often come from an apparently clear and normal sky. They are usually concentrated in the lower atmosphere, are weak in character, and last only a short time. Although they may occur at any time of the year, they appear most often on summer nights in calm weather[[VIII-10]]. Summer atmospheric conditions, in which the air is relatively quiet but varies in temperature and moisture content, have an adverse effect on radio and radar transmission and produce many of these ghost returns.
The uneven distribution of temperature and humidity in the atmosphere is only one of the many possible causes of the radar angels often labeled as saucers[[VIII-11], [VIII-12]]. These ghosts may be produced by peculiar atmospheric conditions, back and forward scatter of radio waves[VIII-13], smoke, wind-carried debris, moisture-laden clouds, ice crystals in clouds or air, lightning, meteors, the Aurora Borealis, birds, insects, bats, electronic reflections from the moon, flares on the sun, or by “chaff” or “window” (foil dropped from airplanes). A radar operator once picked up a group of phantom echoes that seemed to form the letters “GI” which, according to the scope, apparently stretched over a distance of about eighty miles. He tracked them for two hours, but gave up trying to interpret the message when he learned that it was produced by chaff dropped from an Air Force plane during an experiment.
An extremely unusual pattern of “angels” (see [Plate IVc]) appeared on the radarscope at Schilling Air Force Base at Salina, Kansas, on September 10, 1956, and was attributed to forward scatter from atmospheric eddies to ground targets and back[[VIII-13]].
Many radar angels are caused by insects and birds. Their detection on sensitive, high-resolution, Q-, K-, and X-band radars has been verified both observationally and theoretically. Since a radar set surveys a very large volume of the atmosphere and maps it on a relatively small dial, a surprisingly small concentration of insects can cause appreciable clutter on the scope. On sets such as the 0.86-cm TPQ-6 (Cloud Base and Top Indicator), a single insect of detectable size in a volume of 100,000 cubic feet of air is enough to fill the scope with return[[VIII-4]]. Since the guilty insect would be invisible both to ground observers and to the crew of pursuing jets, a flying-saucer report inspired by the radar echoes would remain forever an “Unknown.”
Birds can cause substantial echoes on many radars. Large birds at a distance of ten miles can give signals equivalent to those from a medium-sized aircraft at a distance of fifty miles; in fact, even the fading and fluctuation resemble those of aircraft echoes. On radar, a sea gull may cause a return equivalent to that of a quart of water flying around. The radar cross section of the blip may be several times larger than the geometric cross section of the bird, so that a single adult sea gull at a distance of twenty nautical miles gives a very large radar return. As few as eight birds per square mile can completely fill a PPI (Planned Position Indicator) scope with return[[VIII-14]]. If conditions were exactly right, the birds might be visible to an observer and the source of the angel would thus be explained. But if no one happened to see the birds, the “mysterious” returns could serve as a basis for still another report of invisible flying saucers.
Birds have also been responsible for some of the “ring” angels that have been interpreted as fleets of invisible spaceships. In September 1953 several radar sites in England picked up unidentified objects apparently encircling the city of London. They performed peculiar maneuvers including, according to one saucer publication, the formation of the letters Z and U of the English alphabet. How the correct orientation of this invisible sky writing was determined has never been explained. If the letters are turned top to bottom, back to front, or rotated 90 or 180 degrees, they take on new meanings. Scholars might well argue about whether the first giant symbol should be interpreted as a Roman Z, a Roman N, a Greek Ζ, or a Russian И; and whether the second symbol should be read as a Roman U, a Greek Ω, the mathematical symbol ⊂ standing for “is contained in,” or a Roman C lying on its side.
On the scope, ring angels produce outwardly expanding rings and arcs that sometimes move on and off the screen at incredible speeds. Such echoes have been a fairly common phenomenon in England since 1940 and 1941[[VIII-15]], and experimental research has shown that many of those occurring at dawn or at dusk are caused by flocks of starlings. At dawn thousands of starlings leave the roost in waves at intervals of about half a minute. The birds in each wave are often closely packed in a tight circle or semicircle as the wave ascends. All are flying outward, dispersing in all directions, so that the ring diffuses rapidly on the radar screen and disappears, but is followed almost at once by a new ring. At dusk the birds may return separately to the roost during the course of an hour. Sometimes, however, they assemble first in a field some distance from the roost; they finally take off at the same time as a group and head for the roost in a single giant wave, causing a tremendously impressive but quickly vanishing angel on the radarscope.
Ring echoes observed at Texarkana, Arkansas, have been traced to the movements of red-winged blackbirds. Thousands of birds flying out from a common roosting ground a few minutes before sunrise show up on the PPI scope as an expanding ring that grows broader and more diffuse with time until the composite echo breaks into individual ones and fades at a distance of twelve to thirty-five miles[[VIII-16]].