Meteorological Factors in Unidentified Radar

The University of Arizona, Tucson, Arizona

Meteorological Factors in Unidentified Radar Returns

14th Radar Meteorology Conference
American Meteorological Society

November 17-20, 1970

James E. McDonald

1. Introduction:

Radar meteorology might be said to have its earliest roots in
attempts to account for unexplained echoes detected with Navy
shipboard CXAM radar on the U.S.S. Yorktown 450 miles off the
southern California coast in the summer of 1940 (Page, 1962).
The echoes were demonstrated to be multiple-sweep returns from
the distant San Diego coastal area, seen via the now notorious
anomalous propagation (AP) conditions prevalent in that area.

Similarly, productive research on what ultimately proved to be a
wide variety of types of "radar angels" stemmed from efforts to
account for peculiar echoes not identifiable as aircraft or
precipitation or ground returns. Lightning echoes went through a
similar period of existence as unidentified returns, as did
those caused by intense tornado vortices, sea breeze fronts,
etc. Clearly, unidentified radar returns, and the meteorological
factors contributing to them, have provided a fruitful source of
stimulating new problems in radar meteorology over the past
three decades. Perhaps the most recent example thereof is found
in current studies of the meteorological implications of the
astonishing breaking-wave echoes seen on certain ultrasensitive,
ultra-high-resolution radars, such as the new CW/FM vertically-
pointing set developed at the Naval Electronics Laboratory. The
curious scalloped and braided echo-patterns went unidentified
for a time after being first noted some years back, but are now
reliably attributed to index discontinuities whose shear-
generated undulations and refractivity variance must come as a
distinct surprise to every meteorologist on first seeing graphic
records of these phenomena. In these and other cases of
initially unidentified radar returns, experience has shown that
close attention to recurrent features of the patterns of
puzzling returns has paid off in new and important understanding
of the atmosphere and its electromagnetic propagation
characteristics.

The present paper will comment upon and cite some examples of a
category of unidentified radar returns that do not seem to be
well-known to investigators in radar meteorology, despite the
fact that the phenomena have frequently been attributed to
anomalous propagation and other weather effects. These are a
type of returns observed on operational radars, chiefly military
and air traffic radars, intermittently over a period of about
twenty years, yet never subjected to any very careful,
systematic, and extended scientific scrutiny, as near as I have
been able to ascertain.

2. Past Studies:

It is to be understood that I exclude from this discussion (a)
all really extensive layer-type returns of the sort now fairly
familiar to radar meteorologists from many studies, (b) dot-
   angels of both wind-independent (insects, birds) and wind-
   dependent (atmospheric refractive anomalies) types, (c) ring
angels, and (d) intense but generally really extensive and only
slowly changing ground returns due to AP. After that
elimination, there still remains a class of wind-independent
returns, often highly localized and often exhibiting apparent
speeds of propagation well above ambient wind speeds and
sometimes even well above known aircraft speeds. In Plank's
(1956) review of angel phenomena, he appears to have been
cognizant of such a residual class, which he labeled Type III
Angels ("Echoes, frequently erratic-moving, from localized, non-
   wind carried sources"). That he had in mind returns of the
category here under consideration seems further confirmed by his
subsequent treatment (Plank, 1959, p. 23) of what he termed "a
type of non-aircraft echo that suddenly appears, moves for a
matter of minutes in a semi-straight line path at velocities of
some 600-2000 mph, and then disappears." Echoes of this nature
were discussed earlier by Borden and Vickers (1953) following
two widely publicized episodes at Washington National Airport on
July 19 and 26, 1952. (See also Air Weather Service, 1954.)
Plank (1958) has also briefly discussed those two episodes and
described the prevailing conditions as "exceedingly super-
refractive." However, my own computations of the relevant N-
gradients in the weak surface-inversion layer present showed a
value of only about half the ducting value, and subsequent
checks by Plank (personal communication) revealed that a factor
of two had been inadvertently omitted from his earlier
computations when his estimated gradients were in error by a
factor of two, on the high side. Thayer's gradient computations
confirm this (he does show a thin duct on 7/26/52, but its
elevation of 1 km essentially rules out trapping), yet he too
attributes the episode to AP, which is difficult to understand.
To my present knowledge, the only discussion of any substantial
number of cases in the category of unusual radar returns to be
considered here is that of Thayer (1969), presented as part of
the University of Colorado's study of unidentified flying
objects (UFOs). Since Thayer attributes many of his cases to AP,
his analyses are of present interest. Blackmer et al. (1965)
ostensibly addressed themselves to the present category, but in
fact do not discuss a single specific instance that falls in the
class of interest here; they merely review known propagation
anomalies. Hardy (1969) has also described unusual radar echoes
in a symposium whose context was that of the long-puzzling UFO
problem; but all of his examples, like those touched on by
Blackmer et al., were drawn from categories of known types of
angels and gravity-wave effects and none from the category here
under discussion, In the same symposium, I discussed in
considerable detail (McDonald, 1969) four specific cases in the
category of present interest, two of which cases Thayer (1969)
had attributed to AP effects. I gave reasons for rejecting such
an interpretation (McDonald 1969). For brevity, the category of
present interest will be referred to as "radar UFOs" in the
remainder of these remarks.

3. Some Illustrative Examples of Radar UFOs Attributed to
Atmospheric Effects:

We do face a semantic problem here as to what shall be
understood by the term "radar UFO." I would emphasize, first, as
did Plank in describing his "Type III angels", that they must be
discrete echoes (often as intense as or more intense than,
conventional aircraft at corresponding ranges); and, second,
they must exhibit motions whose kinematic characteristics are
quite distinct from those of conventional aircraft or of
familiar ground-return effects. I would also add a third
stipulation that they must be unlike any of the familiar
interference and ECM effects (spoking, running-rabbits,
blanking, etc.). Those three stipulations may at least be
suggestive of relevant elimination criteria, even if each calls
for much more careful specification than is possible within
present space-limitations. Plank stressed "erratic" motion; but
in many instances of radar UFOs, strong targets have moved in
straight-line paths from one side of an operational scope to the
other at speeds far in excess of aircraft speeds (i.e., several
thousands of miles per hour) without any change of apparent
course. In other instances, high-speed tracks have exhibited
sharp direction-changes, stops, closed one-sweep course-
reversals, or closed orbits at extreme g-levels, in fashion
quite inexplicable in terms of known aeronautical devices.
Plank's term "erratic" is thus somewhat misleading, although
there certainly are cases on record where that description would
fit rather well. His speed range, 600-2000 mph, is not
acceptable here, at either its lower or upper limit. Cases that
I have looked into include targets whose speeds have, within a
single tracking episode, varied from zero to several times his
suggested upper limit. However, I believe that, for initial
purposes of discussion, there is probably rough correspondence
between what Plank referred to as "Type III angels" and what I
shall here term "radar UFOs", though his omission of specific
details of cases he had in mind renders that conclusion a bit
uncertain. Thayer was definitely concerned with the same general
category that I wish to discuss, as will be seen in examples
below; Hardy (1969) and Blackmer et al. (1969), to repeat,
simply were not, in my opinion, treating the present problem.

3.1 Case 1: Kincheloe AFB, Sept. 11-12, 1967:

Between 2242E, Sept. 11 and 0001E, Sept. 11-12, 1967, targets
were observed with an MPN-14 radar (S-band, 60- mile range, 20
rpm scan, beam tilt-range 0-10 degrees) at the Rapcon Site,
Kincheloe AFB, Michigan. The phenomena to be described below
were officially explained as "probable anomalous propagation" by
Air Force Project Blue Book; and Thayer (1969), p. 164)
concludes that this is a "case of observations of moving AP-
echoes produced by unusually well-stratified atmospheric
conditions." Thus we confront here a case of some unusual echoes
that have been attributed to atmospheric effects by two
investigations.

My examination of the episode is based on study of file material
in Air Force archives and on direct interviews with Sgt M. Y.
Burns, the senior radar operator on duty during the episode. It
is relevant to remark that Burns, at that time, had 7 years'
experience in radar, 3 of them at Kincheloe AFB working with the
equipment involved in this case. Useful information on the case
has also been provided by Dr. Norman E. Levine, who was one of
two investigators representing the University of Colorado UFO
Project in an on-site check carried out approximately three
weeks after the incident. Thayer was not at the site, nor did he
interview personnel involved. Like most other cases of interest
in the category of radar UFOs, this one is too involved to
describe in full detail here; but salient futures will be noted,
in order to suggest the kind of problems that I regard as still
unsolved.

A total of 17 targets were followed during the roughly 80
minutes' duration of this episode. On only two occasions were
two targets painting on the scope at the same time; the other 13
were singles. At the time of the appearance of the first target,
a B-52 which was outbound about 30 mi west was being followed
routinely (recounted to me by Levine, confirmed to me by Burns
in direct interview, and confirmed in Blue Book case-file in
archives), when a second blip was noted heading N to S on a
potential collision course with the B-52. The pilot was alerted
but never saw any other aircraft or object. He was asked if he
was "playing with radar" but no ECM was involved. Burns
estimates that the target's initial speed was somewhat faster
than that of the bomber; but then it suddenly slowed to roughly
half its initial apparent speed and the B-52 cleared it, the
target seeming to pass southward behind the aircraft. The blip
then abruptly turned eastward and accelerated to a speed that
Burns and other duty personnel estimated at approximately 2000
mph (1.5 mi/sweep, roughly). Burns could not recall if this
first target crossed the scope; all of his original notes were
given to Levine and hence are presumably in the University of
Colorado archives. Burns told me that this target, like most of
the subsequent targets, was stronger than the B-52 return, and
that he had MTI on and it was taking out all ground clutter. In
response to my query, he stated that he had looked for AP all
that night but saw none at any time. He contacted Minneapolis
ARTC and the ADC SAGE center, but they had nothing on such a
target.

Eight minutes later a second target appeared. (Following data
from official case-file, and only rather sketchy information is
given on most of the targets; but, on directly querying TSgt
Burns, I learned that all were hard targets, not diffuse echoes
of the sort typical of small elements of ground-return from AP.)
This second target was seen at 250 degrees azimuth, heading
towards 50=F8 azimuth, speed not specified in case file. Then
between 2250E and 2330E "nine other UFOs" were observed on the
MPN-14: (1) at 270 degrees tracking towards 90 degrees; (2) at
230 degrees, tracking 30 degrees; (3) at 380 degrees, tracking
100 degrees; (4) at 270 degrees, tracking 90 degrees; (5) at 230
degrees, tracking 30 degrees for 20 miles, then changed course,
heading 360 degrees; (6) at 280 degrees tracking 100 degrees for
20 miles, then turned to 180 degrees. Then these last two
targets (5 and 6) "joined at 30 miles due west of Kincheloe AFB
and both went eastbound at 2000 mph," passing overhead but not
visually observed. (Quote from original TWX from Kincheloe to
Project Blue Book, in case-file.) The remaining three UFOs were:
(7) at 160 degrees, tracki ng 360 degrees; (8) at 30 degrees,
tracking 200 degrees; and (9) at 30 degrres, tracking 270
degrees. Then, at 2338E another target was picked up at 200
degrees, tracking 360 degrees. At 2358E, another at 280 degrees,
tracking 120 degrees from 60 miles out until 20 miles out then
turned and headed towards 270 degrees.

At 0000E (on the 12th), Burns logged the second of two instances
in which two unidentified targets were on-scope concurrently.
One was at azimuth 200 degrees, tracking 90 degrees but then
turned to a heading of 360 degrees, slowed down over an interval
of 8 miles, turned to a 270 degrees heading, and "disappeared
from scope" (sic). The second of the two was at 250 degrees
initially, and tracking 90 degrees, but then turned towards a
heading of 360 degrees and left the scope.

Finally, the seventeenth observed anomalous target, detected at
0001E, was first picked up at 270 degrees, tracking 30 degrees,
but turned to a 360 degrees heading, slowed down, turned to 270
degrees, then turned again to a 360 degrees heading, and speeded
up again.

The case-file includes further comments and clarifications Lt.
T. E. Leaman at Kincheloe and Lt. W. B. Stoecker, ADC (SAGE)
Duluth, as well as by Blue Book officers. These include the
statement noting that the sergeant who reported the sighting "is
very experienced and would probably know what it was if it was
anomalous propagation," and statements that no interceptor
scramble from Kincheloe was called because no scramble
capability existed there, while none was called from SAGE Duluth
because their remoted scopes did not show the unknowns (with
single exception of a strobe seen from the 753rd AC&Wron near
Sault Ste. Marie). Stoecker suggested that the objects may have
been too low over Kincheloe to be seen from the SAGE sites; on
the other hand, as the file states (and as Burns stressed to
me), tower personnel at Kincheloe saw nothing visually despite
good visibility and only scattered high clouds, which is
puzzling, though by no means unprecedented. Burns tried beam-
tilting and tended to get stronger returns at high than at low
tilt. No RHI equipment was locally available, unfortunately. The
case-file states that Sgt. Burns tried switching channels, as a
cross-check against possible ECM, but got no change in target
intensity, tending to discount that possibility. I asked Burns
if he tried IFF, and he said he did but got no IFF, just skin-
return. He pointed out that the 752d AC&Wron at Empire, Mich.,
queried him at one point during this episode, asking if he was
getting a retum at about 100 mi SE, heading his way. But his
MPN-14 had only 60-mi range and could not then detect it; nor
did a target subsequently enter his scope from that sector. The
only target that he carried which he knew to be concurrently
carried by another radar was one at a bearing of about 250
degrees from Kincheloe that was also seen at least briefly by
radar at the 753d at Sault Ste. Marie. Burns recalled that the
753d had a height on that target, but they did not release it to
him. There is no indication in the casefile that this important
point was checked by anyone.

Because targets in the radar UFO category have often been
reported to stop for variable periods of time, I asked Burns
what he felt the slowest speed had been. He replied that in
several instances some of these targets hovered motionless for a
time of the order of 10-15 seconds (3-5 scans). The MTI was set
to function out to approximately 15 miles; whether the hovering
targets lay within or beyond the MTI limit is not now clear.
What interpretation is to be put on a radar episode such as the
above? At Project Blue Book, the considerable experience of the
senior man on duty and his specific yet unsuccessful search for
AP symptoms were rather casually ignored in the following
evaluative comment by V. D. Bryant, dated 15 January 1968 and
included in the official case-file: "The obvious 'excuse' or
'explanation' for the sightings appears to be temperature
inversion. The erratic courses taken by the 'objects', their
wide variations in speed (150 to 2000 mph), and the fact that no
noise was heard, even at the low altitudes assumed, all point
toward anomalous propagation due to temperature inversions."
And, on that basis, the Kincheloe sighting is so carried in the
official files. This is a representative Blue Book radar
evaluation, I have found.

Thayer (1969), reviewing this case in the Condon Report, states:
"This is a good example of moving radar targets that cannot be
seen visually, where there is a 'forbidden cone' over the radar
site. Some of the returns were even seen to approach within 5-15
mi of the radar and disappear, apparently subsequently
reappearing on the other side of the radar scope at about the
same range that they disappeared. This sort of behavior is
symptomatic of AP-echoes." [That gross misinterpretation of the
blind spot over-head in all search-type radars is made by Thayer
in other cases he analyzes in the Condon Report, including the
extremely significant Lakenheath case of 1956 in England
(Thayer, 1969, p. 163).]

Thayer displays refractivity profiles for the time and general
vicinity of the Kincheloe episode and, on the basis of an
elevated duct in the 300-500m layer, suggests that "strong
partial reflection should be expected," and that "moving AP-
echoes, produced in the manner described by Borders and Vickers
(1953), could be expected to appear at apparent heights of
between 2000-3000 ft and 7000-9000 ft." Confusingly, those
heights do not match either of the diagrams he displays, one of
which is, in fact, labeled 9 Nov. 1967, a month and a half after
this episode. Also, Thayer systematically plots his index
profiles on A-Z coordinates, yet always labels the super-
refractive layers in terms of the vertical N-gradient, not the
A-gradient. This is more than merely confusing; it promotes the
misinterpretation that ducting is present in cases (numerical
value between about -115 km^-1 and -157 km^-1), where it really
is not.

A basic difficulty in examining the validity of Thayer's
assertion concerning "strong partial reflection" is that he does
not define his usage of that term. In usual practice, it has
acquired two distinct meanings: (1) Partial direct reflection,
i.e., back-scatter, to put it more precisely, or (2) partial
forward-scatter. Neither of those interpretations offers any
hope of accounting for the kinematics of the reported Kincheloe
targets, and certainly the former could not conceivably yield
apparent radar cross-sections rather greater than that of a B-
52, as Sgt. Burns characterized the intensities of these
unidentified returns.

Nor does Thayer clarify his position by seeming to equate
"strong partial reflections" with the ideas proposed by Borden
and Vickers (1953). Their discussion postulates essentially
specular reflection from moving waves on an inversion surface,
the propagation speeds being of the order of the wind speed and
the apparent targets thus being assigned roughly twice the speed
at inversion level, for reasons of simple relfection-geometry.
First, it must be remarked that, although the Borden and Vickers
report has often been cited as if it settled the July, 1952
Washington radar UFO episodes, I find that view unsupported by
the very sketchy and entirely qualitative mode they propose.
Secondly, the upper-level winds at Kincheloe that night were
less than 10 kts up to the 850 mb level (below which lay the
only index gradients of any significance), which would scarcely
account for the reported target speeds on anything remotely like
the Borden-Vickers hypothesis. And third, the Borden-Vickers
hypothesis of "glint" reflections from favorably disposed
undulations on an inversion surface could scarcely be invoked to
account for apparent target movements, whose directional
variability matched that seen on the Kincheloe MPN-14 during
this episode; nor could it possibly account for sudden turns,
hovering, and accelerations described in the official case-file.
Other slightly subtler objections could easily be raised, but
those simple ones seem sufficient to reject Thayer's loose
explanation (let alone the still less meaningful one contained
in the official case file).

One might ask how Thayer would suggest that any form of
propagation anomaly or "partial reflection" could explain the
complex kinematics reported by the Kincheloe Rapcon Site for
this night. One partial answer may be that he offers that
suggestion in a mere 4-paragraph account of this intriguing
case, an account that gives the reader no hint that 17 distinct
targets were seen, that says nothing about turns, hovering
periods, or accelerations, that omits any mention of speeds of
the order of 2000 mph, and that gives no suggestion that in one
instance two such targets converged from opposite directions,
turned eastward together, and then moved across the scope side-
by-side at about Mach 3, passing over and beyond Kincheloe AFB.
Unfortunately, I must add that my detailed checking of the
discussions of the 35 "optical and radar analyses" in the Condon
Report has established that such omissions of crucial sighting
details are typical, not exceptional in that Report.

Plank (1958, 1959) has suggested that perhaps some of the
"erratically moving angels" (his Type III) might be caused by
"shock waves, echo being the product of direct back scatter or
diversion of energy to the ground." He then notes that shock
waves are thin, on the order of microns, yet can have refractive
index differences across them of "several hundred N-units." The
high speeds exhibited by some of the targets in this Kincheloe
episode (and in many others of interest) might vaguely suggest
shock phenomena, so perhaps a few remarks negating that
hypothesis are in order. First, Plank really does not offer any
geometric model to support the kind of kinematics found in
interesting radar UFO cases. (Quite possibly he is unaware of
the content of most such cases.) Only extremely simple paths
would be possible; certainly his emphasis upon erratic movement
goes wholly unexplained on any such model. But the greater
objections are the quantitative objections. He mentions N-
changes of several hundred units; but this is quite
unreasonable. First, only temperature jumps and not humidity
jumps could accompany shockwave passage.

Secondly, in the lower atmosphere, one N-unit change is
associated with approximately 1 degree C of temperature change.
Third, the Rankine-Hugoniot equations permit one to relate
shock-front temperature changes to concomitant peak
overpressures; and an over-pressure of, say, 5 psi, is found to
lead to a transient shock-heating of only about 30 degrees C
(hence about 30 N-units jump across shock-front), yet this is an
overpressure not only great enough to take out all nearby
windows but to level weak structures and collapse roofs. In
brief, the only shock waves capable of giving significant radar-
reflecting characteristics would be of rather severely damaging
nature, would leave unmistakable after-effects, and yet could
influence a radar beam for only fractions of a second. The
shock-wave suggestion seems unpromising for explaining radar
UFOs, in general, and the Kincheloe targets in particular.
Indeed, one of the characteristic puzzles of high-speed radar
UFOs (and the Kincheloe UFOs in particular) is that no
discernible sonic boom is associated with cases where the radar-
deduced speeds are markedly supersonic.

In summary, it is by no means clear that one can accept any
known kind of anomalous propagation for targets in the class
exemplified by the Kincheloe targets. However, we are doubtless
still unaware of certain types of propagation anomalies in our
atmosphere, and the breaking-wave echoes may attest to
interesting surprises yet to come. But there seems to exist so
large a margin of separation between any of the now-suspected
atmospheric effects and the characteristics of what I am terming
radar UFOs that I do find it difficult to understand how AP and
"weather effects" have so long been casually employed to explain
radar unidentified targets within Project Blue Book, and how
they have more recently been invoked in the Condon Report by
Thayer in essentially similar manner.

Perhaps a clue to the latter is found in a curious introductory
definition of what Thayer (1969, p.117) terms "blip-like" radar
returns: "Cases where the radar target (or targets shared
characteristics similar to the return from a solid object (such
as an aircraft, etc.) and where the target did not display
erratic or discontinuous behavior. Acceleration or velocity in
excess of known aircraft capabilities, or periods of immobility
were not considered to be contrary to normal target behavior." I
fear that this definition be paraphrased fairly by saying that
Thayer adopted at the outset explicatory rules by which
completely abnormal radar returns were agreed to be quite
normal. Many examples in support of such a paraphrase have come
to my attention in follow-up investigations of the Condon
Report, whose handling of the radar UFO cases I find almost
wholly uncritical, generally tendentious, and often absurd --
and, more than that, disturbingly incomplete with respect to
the scientifically most puzzling features of many of the cases
(cf. McDonald, 1969). If we are to learn anything
meteorologically interesting from radar UFOs, it will come only
from much more discriminating and more thorough analyses than
any now at hand.

3.2 Case 2: U. S. Naval Air Station, North Island, San Diego,
Calif., Oct. 14 1957:

As another illustration of past radar UFO cases that have been
officially explained in terms of meteorological effects, we
might consider one that, unlike the preceding case, involves
visual as well as radar observations, and for which the radar
observations were made from the air rather than from the ground.
Cases of both the latter types are scattered through the Air
Force archives, and some, like this one, emanated from another
service. I have not interviewed any of the observers in this
particular case, so, in order to fulfill written agreements with
the Air Force, I cannot cite witness-names. Instead, I shall be
forced to use merely initials of the Navy personnel involved. (I
am currently challenging Air Force structures against citation
of names of military and government-agency witnesses in past UFO
cases, contending that they are blocking full and credible
scientific discussion of case details and arguing that these
strictures stand in violation of P.L. 552. It is the present Air
Force position (SAFOI letter, 7 Aug 1970) that scientific
citation of witness names would constitute an "invasion of
privacy", despite the fact that these were personnel of the
military, FAA, USWB, etc,, whose observations and official
reports were made in regular line of duty. At this writing, my
efforts to get the Air Force to rescind these strictures have
not yet proved successful, so unfortunately I am obliged to omit
all names from this account of my checks on this scientifically
significant case.

No strictures against citation of names of investigative and
evaluative personnel have ever been imposed in the course of my
investigations, so I do cite certain names in those categories,
since they, too, are of obvious documentational relevance.)

Slightly before 1900 PST, on October 14, 1957, at NAS North
Island, AC/3 VEE (initials of enlisted Navy tower controller)
noted "a bright, round, white light, about the size of a dime,
bearing 210 degrees T from the tower and approximately 300 ft
above the Point Loma land mass," according to a 17 October 1957
report to the Air Force Office of Special Investigations from
the District Intelligence Officer, Eleventh Naval District. VEE
observed the object remain stationary for about 2 minutes and
then fade out. One or two minutes later a similar light,
presumably the same, suddenly reappeared slightly farther north
and a bit lower than before, and now somewhat brighter. After
remaining stationary about two minutes, it again faded away, the
report notes. Somewhere in this sequence, VEE alerted two other
enlisted personnel, DC and MD, also on duty in the tower; and
all used binoculars in the later portions of the visual
observations, according to the intelligence summary. It soon
reappeared once more, again farther north and again lower; it
seemed now to wobble slightly and exhibited a half-halo on its
upper portion, with a bluish tint on one side. No angular
estimate is given.

Concurrently, a Navy S2F tracker (anti-sub-marine search
aircraft), attached to VS-21 at NAS North Island, moved into
position for takeoff, and AC/3 VEE had to divide his attentions
between the unexplained light over Pt. Loma and the S2F ready
for takeoff. In the process of controlling the takeoff and
vectoring the aircraft to attempt a search, VEE lost the object,
the reasons becoming clearer below.

According to Air Intelligence Information Report 01-03-57, dated
23 October 1957, prepared by Maj. L. W. Bruner, 27th Air
Division, Norton AFB, Calif., based on a signed summary
statement by the S2F pilot, Lt. ALR (initials), the aircrew,
during engine warmup, had heard the tower operator take three
radio calls to an "unidentified aircraft", requesting identity
and intentions, but getting no reply. On requesting and getting
takeoff clearance, Lt. ALR was asked by the tower operator to
maintain 200 ft altitude after liftoff and proceed to Pt. Loma
to identify a stationary light source apparently hovering at
that estimated altitude. Lt. ALR notes that both the copilot,
Lt.(jg) GTC, and he observed the light, while still on the
runway before starting their run.


"After take-off, I turned outbound over the channel," Lt. ALR
wrote in VS-21 msg 152348Z of Oct 1957, "and climbed to 200
feet, all the while keeping the light in view. My intentions
were to proceed seaward of the light so as to silhouette its
airframe against the lights of San Diego. However, when we drew
abreast of it off our right wingtip, we observed it undergoing a
rapid acceleration away from us and to the west. I noted
relative motion between it and the lights of San Diego. As our
range opened the light began to alternately vary in color and
intensity. The extremes were bright red and a blue white, with
no regular period of change from one to the other."

"I turned West and assumed a heading of 230 mag. with the light
then dead ahead. In about four or five minutes (warm-up time)
our radar operator reported a target dead ahead at seventeen
miles and above us. The weather was clear ahead and above, with
a discernable horizon and low clouds 30 miles west. The stars
were bright and clear but small and dim compared with the light
we were following. During the chase there was always evident a
relative motion between this object and the background of
stars."

"From Pt. Loma on out the object climbed steadily and I followed
in a gradual ascent at 240 knots IAS, closing irregularly. At
4500 ft the object leveled off 12 miles ahead, and then drifted
right 10 degrees in about five seconds. I turned right to 240
mag., leveled off and increased speed to 160 knots. The range
closed to 10 miles and stabilized. After following for about
three minutes at 10 miles I decreased speed to 120 knots but
observed no range-rate on radar. I then advanced speed to 180
knots IAS and still observed no range-rate."

"The object in the meantime drifted 20 degrees to the left (220
mag.) in no more than 10 seconds, and then closed range to 8
miles in one rotation of the radar antenna (7.5 seconds). The
range stabilized again at 8 miles and we began another gradual
climb. At 8000 ft and about 40 miles from Pt. Loma the object
leveled off and shortly after disappeared visually and on radar.
Fifteen seconds later it reappeared visually but not on radar
although the operator switched to sector-scan and searched
continuously."


Lt. ALR concluded his summary with the comment that they
maintained visual contact until the S2F was 50 miles from Pt.
Loma, at which time they lost visual contact, too (fadeout),
terminating the incident. His statement notes that all four
aircrewmen saw it and can substantiate his descriptions. (The
two enlisted men aboard were WES and WPC.)

This is only one more of many radar UFO cases I have recently
been studying as a result of extensive searches through the Air
Force archives and only one of many hundreds of UFO cases I have
checked during the past four years. Each case has certain unique
features, but many have the common feature that it is
exceedingly difficult to propose for them conventional
explanations. Yet, here as in almost all the rest that have
received the Project Blue Book evaluations, a conventional
explanation has been assigned by Blue Book.

I quote from that explanation, extracted from Air Force
archives, since it invokes atmospheric phenomena of potential
interest to radar meteorologists and atmospheric physicists:


"Distortion of light and changing colors attributed to probable
inversion off coast. That Arcturus was the object is ...
indicated by the fact that the pilots could not close on the
object. Its jumping around and the spurious radar returns caused
by inversion or other weather conditions conclusive to
distortion of atmospheric optics. Sighting was of short duration
and Arcturus set at about the time of object's disappearance."


(Actually, I must note that there is a slight confusion on the
official evaluation of this case, Although the above case-
summary explains the sighting in terms of Arcturus and some form
of anomalous propagation, the casecard in the archives shows it
as "Possible Balloon." There is no evidence of any real analysis
of either hypothesis, no weather data, no computations of
positions, or other quantitative assessment; but the original
teletype message from AIRASRON-21 to Wright-Patterson AFB, which
notes how the object "drifted across chase plane's course at
speeds estimated by pilot to be in excess of 1000 mph," has a
pencil-sketch of a top-view of an aircraft flying past a sphere,
with arrows and lines evidently intended to depict the viewpoint
contained in evaluating annotations that nearly obliterate parts
of the TWX: "Tests have shown that when a/c slipstream from wing
tip hits balloons it sends it rapidly sideways." The sketch and
pencilled evaluative comments, typical of many documents in the
UFO archives, are signed by Capt. George T. Gregory, who was
Project Blue Book officer in the 1957-59 period. Many of such
UFO reports were processed in about this way over the years.

But this one has the alternative (and evidently officially
preferred) explanation of suggested inversion effects on
Arcturus and the S2F's radar. Consider certain difficulties with
that explanation: (1) The tower observers reported to Navy
intelligence interrogators that the light shifted three times,
from its azimuth of first appearance at 210 degrees T. At about
1900 PST on this date, Arcturus was nearing the horizon at about
290 degrees T. This light over Pt. Loma was seen by the cockpit
crew from the runway and held in sight until they drew nearly
abreast of it, viewing it off the right wingtip, whereupon it
suddenly accelerated westward and started climbing. (2) The
subsequent air chase involved a sequence of pursuit headings
stated to be 230 degrees mag, then 240 degrees mag, then 220
degrees mag, the source finally pulling away and fading out at
230 degrees mag, after an approximately 20-minute visual-radar
chase, at about 230 degrees mag. The magnetic variation off the
San Diego coast is about 15 degrees E, whence the bearing to
Arcturus would have been about 275 degrees mag, some 35 to 50
degrees from the luminous object's reported azimuth, far in
excess of uncertainties that would affect observations under
these conditions. (3) Viewed from the S2F, the object appeared
to climb, then level out, on two occasions. And it executed fast
lateral shifts to both left and right, through arcs stated by
the Navy pilot to approximate 10 degrees and 20 degrees of
relative azimuth. (4) The aircraft was flying, after the first
few minutes, at altitudes well above the coastal subsidence
inversion whose refractive effects are adduced in the official
explanation to account for angular image-excursions whose
amplitudes dwarf the 10's of seconds of arc displacement
associated with stellar scintillation effects, even under
unfavorable viewing conditions at the surface, let alone at 4-
8000 ft level. (5) Nor does the official explanation that the
"inversion and weather conditions" were responsible make better
sense of the reported radar behavior. Ranges opened and closed,
angular altitude varied, and azimuths shifted, all this during a
40-mile pursuit, at altitudes ultimately near 8000 ft. (6) The
estimated lateral speeds (order of 1000 mph) came from rough
calculations based on radar ranges, plus compass-based angular
estimates. A target at 10-mile radar range that moves 20 degrees
in 10 seconds has exhibited an apparent velocity near 1200 mph.

To suggest that optical refraction effects plus anomalous
propagation could cause such extreme behavior, and to suggest it
without the slightest supporting argument, is simply not
reasonable.

Could there be some truly phenomenal optical and radar-
propagational anomalies of the atmosphere that might be capable
of yielding visual and radar indications of this sort? The
archives have many more such anomalies that will require at
least equal extensions of present scientific knowledge if we are
to account for them along the lines of application of
atmospheric physics that I have found typical of Project Blue
Book UFO explanations over the past two decades.

3.3 Case 3: Gulf of Mexico, B-29, Dec. 6, 1952:

With so large a number of previously unknown cases that I could
discuss and so little space available here, it is difficult to
select a final example. But because of my strong concern over
the serious inadequacies of the radar-optical UFO case-analyses
in the Condon Report, I choose a last one that exhibits some of
those deficiencies, that is explained in terms of alleged
atmospheric effects, and that happens to be a rather famous case
in UFO annals. I believe that the ad hoc panel that reviewed and
endorsed the Condon Report (NAS, 1969) could not possibly have
scrutinized carefully the level of analysis of cases such as
this in that Report, a point that I have elaborated elsewhere
(McDonald, 1969b).

In the early morning hours of December 6, 1952, a B-29, on the
return leg of a training flight out of Randolph AFB had turned
around over Tampa and taken up a generally westbound course
across the Gulf. When about 100 miles south of the Louisiana
coast at an altitude of 20,000 ft, visual sighting of oilwell
flares on the coast led the Instructor Navigator, 1/Lt WN, to
request a student radar operator to turn on his set and try to
pick up the coastline on 100 mile range. After the student
operator's failure to detect the coast, WN confirmed that no
coastline echo was discernible, so called for a set calibration.
Some time later he was alerted to presence of some four blips
ahead and in rapid closure with the B-29. [Air Intelligence
Information Report No. IR-86-52, filed from Randolph AFB by Maj.
J. R. Sheffield, Wing Operations Officer, 3510th Flying Training
Wing, includes a summary of the events, the sightings, a map,
and signed statements by three officers and two enlisted men who
figure in the incident. These items, plus the original TWX and
other materials in the archived case-file indicate that the B-29
had turned to a heading of 320 degrees at some earlier time,
after the unsuccessful search for the coastline on the
navigational radar, and had reached coordinates of 28 degrees
10'N, 92 degrees 04'W when the sightings began. I cite these
points because they are quite relevant to a point that Thayer
(1969) regards as crucial, yet seem to me to be a
misinterpretation of the intelligence report. I infer from
coordinates and times that inability to pick up the coastline
occurred while the B-29 was still just over 100 miles offshore,
beyond the set's 100-mile range. Furthermore, the set was then
uncalibrated, as the Instructor Navigator makes clear in his
signed statement.]

The first 4 targets were sighted at 0525 CST, "with no specific
grouping such as a radar beacon transmits apparent on the scope
at 330 degrees," Lt. WN stated. The radar had azimuth
stabilization; its scan rate was 25 rpm. The navigator, 2/Lt
RKE, verified WN's assertion that these first blips advanced
southeastward about 5 mi/scan, and MSgt BRP, the aircraft
performance technician, using 1/Lt NK's stopwatch data and the
indicated displacements per scan, informed the crew that the
computed target speed was about 5000 mph. These targets, viewed
on three repeater scopes, passed to the right of the B-29 and
moved offscope at a bearing of about 70 degrees.

Then, immediately after a calibration-check, a second group of
blips was seen coming in along a similar path. This time the
pilot called off relative bearings from his repeater scope, with
instructions for the crew to watch on the starboard. SSgt WJD
states: "I immediately looked in that position (3 o' clock
bearing called out from cockpit) and saw two flashes of
approximately 3 seconds, which did not alter course whatsoever.
The flash was of a blue-white nature and did not change
brilliance... when it disappeared." Two objects were also seen
by MSgt BRP, and he was evidently forward for he saw them move
rearward and disappear under the wing. In 1/Lt WN's accounc, he
confirms that these flashes were seen to "go from front to rear
under our wing "

The interrogating officer, Maj. J. R. Sheffield, in his
intelligence report from Randolph AFB, gives 18,000 ft as the
approximate altitude of the objects and 20,000 ft as the B-29's
altitude, accepting the crew's statements that the objects came
in below the B-29. Despite this, Sheffield states in his report
that: "Visual sightings are indecisive an of little confirmatory
value," but no explanation of why he discounts the two crewmen's
observations is given. Like many other Blue Book reports, this
case-file leaves unanswered a number of pertinent questions. The
total number of objects followed on radar is not clearly
specified. 1/Lt NK says he observed: "about twenty objects in
all, sometimes as many as two and three on the scope at one
time." Crewmen refer to one radar-observed event involving a
merger of targets (a feature that I have now found in a number
of reports of radar UFOs). As WN described it: "Contact was
broken off at 0535 after a group of blips merged into a half-
inch curved arc about 30 miles from our a/c at 320 degrees and
proceeded across the scope and off it at a computed speed of
over 9000 mph." WN also stresses one other significant target-
movement: "One group of blips, after the scope was calibrated,
were noted, after moving from 330 degrees to 150 degrees across
the scope, to arc about and swing in behind us at approximately
30 miles and maintain speed and distance for approximately 10
seconds and then disappear." Given that summary, consider
Thayer's (1969) explanation of this case (which Blue Book has
carried as "unidentified" since 1953): "The visual sightings
were probably Geminid meteors," he writes. No supporting
discussion; just that assertion. In fact, one finds that the
radiant of this December shower lay at about 280 degrees azimuth
and about 55 degrees elevation angle at 0535C on this date.
Hence, any Geminids seen to the starboard of an aircraft on 315-
320 degrees heading at 0530C would have been descending almost
perpendicular to the NE horizon, a 90 degrees direct mismatch
with Thayer's explanation.

The above-described multiple radar target events Thayer explains
in terms of a ducting layer that showed on the 0900C Burwood
radar. "The strange moving targets seen on the radar were
probably caused by imperfections in the atmospheric layer
forming the radio duct allowing radio energy to enter the
ducting layer at various points. This would create sporadic
returns." The failure to pick up the coastline just prior to the
UFO episode he explains as follows: "A transmitter located above
a radio duct and emitting a high enough frequency to be
affected, as the radar undoubtedly was, does not excite
propagation within the duct. This implies that the coastline
below the duct would not be visible to the radar located above
the duct." Thayer's argument is, of course, quite erroneous; he
has his argument upside down. And casual suggestion that the
complex target behavior reported in this case was the result of
"a series of gravity waves running along the duct" is mere
verbalism.

Thus were radar UFOs discounted in the Condon Report. Perhaps
the above examples will give at least some indication that there
remains an unsolved scientific problem here, that there exist
unidentified radar returns of a category for which atmospheric
effects have been proposed as explanations, but on ground that
are to date less than satisfactory.


REFERENCES:
=B7 Air Weather Service, 1954: Radar objects over Washington. AWS Bulletin,=

Sept., 42-57.
=B7 Blackmer, R. H., et al., 1969: Radar and the observation of UFOs. In
Scientific Study of UFOs, E, U.
Condon, princ. inv., Bantam Books, 965 pp.
=B7 Borden. R. C,, and T. K. Vickers, 1953: A preliminary study of
unidentified targets observed on Air Traffic
Control Radars, CAA Tech. Div. Rpt. 180, Indianapolis, 16 pp.
=B7 Hardy, K, R., 1969: Unusual radar echoes. Presented at UFO Symposium,
136th meeting AAAS, Boston,
Mass., 26-27 Dec.
=B7 McDonald, J. E., 1969a: Science in default: 22 years of inadequate UFO=

investigations. Presented at UFO
Symposium, 136th meeting AAAS, Boston, Mass., 26-27 Dec.
=B7 McDonald, J. E., 1969b: Review of the Condon Report. Icarus, 11,=
443-447.
=B7 National Academy of Sciences 1969: Review of the University of Colorado=

Report on Unidentified Flying
Objects. Icarus, 11, 440-443.
=B7 Page, R. M., 1962: Origin of Radar. Doubleday, N.Y., 196 pp.
=B7 Plank, V. G., 1956: A meteorological study of radar angels. Geophys.=
Res.
Paper No. 52, AFCRL, 117 pp.
=B7 Plank, V. G., 1958: Atmospheric angels mimic radar echoes. Electronics,=

31, March 14, 1958.
=B7 Plank, V. G., 1959: Spurious echoes on radar, a survey. Geophys. Res.
Paper No. 62, AFCRL, 51 pp.
=B7 Thayer, G. D., 1969: Optical and radar analyses of field cases. In
Scientific Study of UFOs, E. U. Condon,
princ. inv., Bantam books, 965 pp.