EXCERPTS FROM A 1966 LEnER TO CONGRESSMAN L. MENDEL RIVERS, CHAIRMAN, HOUSE ARMED SERVICES COMMinEE, FROM SECRETARY OF THE AIR FORCE HAROLD BROWN REGARDING UNIDENTIFIED FLYING " ... Within the Depa1t:ment of Defense the Ai1 F orce has the 1es1Jonsibility of investigating ?'epo?ts on unidentified flying objects and of evaluating cmy possible th1eat to our national secmity that such objects ?night 1Jose. In ca?'?"'fing ottt this 1esponsibility let me assu1e you that the Ai1 F01ce is both objective and tho1ough in its t?eatment of all ?'epo?ts of unusual aerutl objects ove1 the United " ... In 01de? to evaluate this StLbject as tho1oughly as possible, the capabilities of the Ai1 F01ce Scientific AdvisO?"'J Boa1d have ?'e- cently been focused U1Jon the subject of UFOs. This Bowd ... cnm- pleted a detailed 1eview of this subject and concltwed that the UFO phenomena p1esents no tlweat to the secwity of the United States, and that the p1esent Ai1 Force 1nogm1n dealing with UFO sightings has been well o?ganized. Recommendations by the Boanl''CL?'e 1nes- ently. unde1 study and w e ex1Jected to lend even st1onge1 e?nphasis on the scientific aspects of investigating the sigMings that wa?"?'ant extensive analysis. "Based upon 10,11,7 ?'eJJO?'ted sightings [1om 1947 t/w()ttgh 1965, (11,~07 th1ough 1966) ... I believe it is significant that the Ai1 Fo1ce has succeeded in identifying 9,50~ (10,582 th1ough 1966) of these objects. Vi1tually all of these sightings we1e de?'ived [101n sub- jective hmnan obse?va.tions and inte?jnetations. The most common of these we1e ast?onomical sightings that incbuded such things as b1ight sta1s, planets, comets ctnd meteo1s, and fi?eballs and am01al st1eamers. . . . I n evaluating these sightings, the Ai1 Fo1ce has used ca?e- fully selected and highly qualified scientists, engineers, technicians, and consultants. These pe1sonnel have utilized the finest Ai1 FO?ce labO?atO?-ies, test cente1s, scientific inst?umentation, and technical equipment [o1 this pU?JJOSe. "Although the past two decades of investigating unidentified fly- ing ob.iects ha-ve not identified nny tlweat to om national secwrity, or evidence that the unidentified objects 1epresent developments o?' p?inciples beyond present-cla.y scientific knowledge, o1 any evUlence of ext?ate??est?ial vehicles, the Air Fo1ce will continue to investi- such phenomena with an open mind nnd with the finest tech- equip?nent availnble." Unidentified Flying Objects (UFOs), or flying saucers as they are known to many persons, have been the subject of consid- erable interest on the part of t he public as well as the U.S. Air Force for two decades. On Dec. 30, 1947, the Air Force was given the res ponsibility by the Department of Defense for investigating UFO sightings. This booklet is intended to meet the needs of individuals seeking information about UFOs. The Introduction is a brief history of UFO reports and studies and provides some informa- tion on s cientific observations and a nalyses. The section "Aids to Ident ification of Flying Objects" is more technica l and should be of interest to persons desiring in-depth information on flying ts and natural phenomena. The "Questions and Answers" section will help answer many of the questions commonly asked about UFOs. TABLE OF CONTENTS AIDS TO IDENTIFICATION OF FLYING OBJECTS ....................... . METEOROLOGICAL AND ASTRONOMICAL FACTORS ..... 11 Sky Search De pth Perception Accommodation Seeing at Night INTRODUCTION UFOs do not constitute a new phenomenon. In 1254 at Saint Albans Abbey, England, an "elegantly- shaped, well-equipped s hip of marvelous color" appeared in the farmer in Texas reported seeing a "dark flying object in the shape of a disk cruising in the sky at a wonderful sp eed" eported sightings were somewhat sparse until K enneth Arnold made world headlines in June 1947 when he described chain of nine fast-flying objects appearing " . . . like saucers ... " near Mt. Rainier, Wash. Scientists examined all the facts presented by Arnold. They determined that weather conditions at the time of the sighting were very stable and were likely responsible for an increa se in the index of refraction * of the atmosphere (Arnold had re- ported the air was "clear as crystal"). After weighing all the available facts, the Ail Force conclu ded that Mr. Arnold had witnessed a mirage created by uncommonly stable weather conditions. During World War II, the strange illusions that sometimes dming unusual atmospheric conditions presented a prob- lem for members of a U. S. Navy tas k force in t he Pacific. Navy spotters r eported a str ange a erial object r a pidly ap- proaching their ship, and opened fire. The ship's navigation officer who was not on the bridge a t the time, heard the guns and quickly returned only to di scover the gunner s were shoot- ing at the planet Venus. Atmospheric conditions had apparently ma de the gunners victims of a n illusion of proximity. * An index of the degree of bending of light rays following Snell's Law as this lig ht or reflection passes from one la yer of atmo.!~pheric density to AIR FORCE RESPONSIBILITY On Dec. 30, 1947, t he Air Force was given the responsibility by the Department of Defense for investigation of UFO sight- ings under the code name "Project Sign." Air Force interest in the investigations, then as now, related diJ:ectly to "its responsi- bility for air defense of the United States. The Air Technical Intelligence Center (ATIC) conducted the investigations. "Project Sign" conclu sions stated in February 1949 hold true to this day: " ... I t is unlikely that positive proof of their (UFO) exist- ence will be obtained without examination of the rewains of crashed objects. Proof of non-existence is equally impossible obtain unless a reasonable and convincing explanat ion is determined for each incident. Many sightings by qualified and apparently reliable witnesses have been reported. However, each incident has unsat isfactory features, such as shortness of time under observation, distance from obser ver, vagueness of de- scription or photographs, inconsistencies between individual observers, and lack of descriptive data, that prevents definite conclusions bei ng drawn ... . " The UFO project continued on a r educed scale, and in Decem- ber 1951 t he Air Force entered into a contract with an indus- trial fi11n for a detailed stud y of UFO cases on file. I t took the company three years to complete the study, which was released under ATIC cover because the company desired to remain anonymous in this field of r esear ch. his r eport, conunonly referred to as "Special Report # 14," evaluated all UFO data in Air Force files. report stated: "It can never be absolutely proven that 'Flying Saucers' do not exist. This would be true i f the data obtained were to include complete scientific measurements of the attributes of each sighting, as well as complete and de- tailed descriptions of t he objects s ighted .... Photo of 1957 Comet, Mrkos, token by Curtiss A. Griffin, helps explain why such phenomena ore often mistaken for "UFOs" or " flying saucers." " ... on the basis of this evaluation of the information, it is considered to be highly improbable that any of the reports of unidentified aerial objects examined in this study represent ob- servations of technological developments outside the range of present-day scientific knowledge." In 1949, "Project Sign'~ was changed to "Project Grudge," and in 1952 the program of investigating UFOs was given its present name, "Project Blue Book." Of the 11,207 UFO sightings reported through 1966, all but 675 had been identified. Many of the unidentified remain in that category simply because sufficient information is not available to complete the studies. During the 20 years of investigations and analyses, photo- graphs have been submitted for evaluation in conjunction with UFO reports. The objects in these photographs have been de- termined to be mostly misinterpretations of known natural phenomena or convention!i-1 objects. Some have been determined to be double exposures, "trick" photography, hoaxes and flaws in negatives or in developing. Se1vices of qualified scientists and technicians have been, and will continue to be, used to investigate and analyze reports of unusual aerial phenomena over the United States. In May 1966 the Air Force took steps to strengthen scien- investigations of UFO r eports. The h elp of more individ- uals within the scientific community was solicited through contracts calling for prompt, in-depth investigation of selected UFO reports. In October 1966 the University of Colorado was selec ted to undertake the investigations under an 18-month contrad. Dr. Edward U. Condon, internationally known physicist, now a pro- fessor at the University, was named to head the study. AIDS TO IDENTIFICATION During the past few years, many flying objects reported as UFOs were later found to be manmade. Balloons and ~ircraft have often been misidentified. For example, an observer who sees a silvery, transparent, disk-like object may be looking at a b~lloon. The absence of exhaust or engine noise, or any visible means of propulsion, upport such identification. Weather balloons are some- times released in clusters and may drift in what appears to be a formation, depe nding on the air cUlTents. They shimmer in reflected sunlight or moonlight, and seem to hover as they pass from one air current to another. Upper air research balloons may attain g~eat heights and travel great distances before they fall back to earth. They may be observed, therefore, in areas far removed from a launching site. Research balloons are usually constructed of material with a highly reflective surface. They are often 200 feet in diameter and are visible, under certain atmospheric conditions, at ex- treme heights. Such balloons, seen in reflected light, may seem d.isk-like in shape and may appear to have an oscillating mo- tion. (They carry radar reflectors which can result in elec- tronic contact.) An observed object is not u sually a balloon if the speed is very fast. However, some balloons travel in the upper air currents at speeds exceeding 100 m.p.h. To help identify a flying object a.s a balloon, the observer should keep in mind that a balloon moves with the wind and not against it. To learn more about atmospheric pressure, temperature wind directi~n and velocity over vast stretches of open sea, b~lloons are bemg launched to fly at 30,000 feet. They are rigged to destroy them~elves if they drop below 28,000 feet, or fail to reach that h eight. These balloons are 40 feet in diameter and have a plastic skin only 2/ 1000ths of an inch thick. Sunlight or moonlight reflecting from their plastic skin surface can cause them to be easily mistaken for UFOs. FIGURE 1: What may appear Ia be a UFO soaring through the sky may actually be an abject such as this weather research balloon. FIGURE 2 : Radar planes may easily be mistaken far UFOs under unusual weather conditions. Because balloons can be observed when the sun is below the horizon and the earth is in comparative darkness, a co nsid- erable number of them have been reported as UFOs over the past 10 years. These UFO sightings were usually made just before dawn or a few minutes after sunset. They were reported to be shaped like "disks" or "spheres" and to be bright reddish- FIGURE 3: G eneral Dynamics B-58 Hustler delta-wing jet bomber. orange, pink, or reddish-white in color. The coloration is caused by the sun's slant rays reflecting off the balloons' sur- A Lockheed EC-121 Constellation early warning picket air- craft is an example of an unfamiliar type of aircraft which, to the uninitiated observer, might appear to be a UFO. Many new types of delta-wing aircraft are in operationa l The unusual configuration of this type of aircraft could cause possible confusion and be reported as a UFO. Lights used on the Boeing KC-135 Stratotanker aircraft for night refueling missions are often mistaken for UFOs in trail formation. The light from a jet tail pipe, under dusk conditions, often misidentified. Other manmade objects and natural phenomenon which have reported as UFOs include: * Conventional aircraft observed from unusual angles; * Modern j et aircraft flying at great speeds and high alti- * Reflections of sunlight, moonlight, and starlight from air- craft and balloons at great heights; * Searchlight reflctions on clouds; * Meteors, comets and stars; * Pla nets obser ved at certain times of the year; * Meteorological phenomena; * Cloud formations; * Birds, especially migratory formations; * Dust and haze; * Kites, fireworks and flares; * Rockets; and * Contrails. What follows is a discussion of some of the factors which may affect the identity of flying objects. Shape i s an important factor in determining the identity of a flying object. Many of the strange shapes of UFOs reported in the past could not be identified in terms of familiar objects, but in many instances could have been reflections from con- ventional objects viewed under unusual conditions. Light and adow produce fantastic distortions, especially when viewed objects are at great distances and bathed in varying degrees of darkness. The four most common shapes of UFOs reported are: (1) Elliptical or disk shape (2) Aircraft shape Cigar shape Propeller shape These varieties of shapes are individual reactions to what may have been familiar or conventional objects seen under unusual conditions, or what was created in the mind of the observer by his physiological limitations and psychological responses. Fatigue, unusual weather conditions and stress can induce such manifestations. One UFO report stated that the object was shaped like a con- ventional aircraft, but was luminous and surrounded by a red glow. This phenomenon could have been a n actual aircraft glow- ing from an unusual play of moonlight or starlight on its metal parts. A disk-like object, 'vith illuminated portholes, could be a conventional aircraft distorted in shape and stripped of wings by a temperature inversion mirage effect and reflecting light from windows. Transparent, cigar-shaped obj ects, illuminated from the in- nd emitting an exhau st, could be jet aircraft at high alti- tudes where they appear win gless. T he mirage effect of a tem- perature inversion could cause the apparent illumination and transpa r ency. Saucer-shaped objects, w hich hover and maneuver erratic- uld be t he planet Venus or Mars seen near t he horizon at certain times of the year. When objects a r e viewed through haze or mist, or hand-held binoculars, the limitations of the human eye can produce what appears to be a hovering effect, or erratic movement. Propeller-shaped objects could be conventional or glider-type aircraft, distorted in sha pe by mirage effects caused by a tem- perature inver sion. METEOROLOGICAL AND ASTRONOMICAL FACTORS Scientists have been exploring the mysteries of the universe for many centuries. Today they know a great deal more about the composition of the galaxy which includes the earth among its many planets, star s and other celestial bodies. Yet, many questions remain unanswered and the search for more knowl- edge in the broad field of astlonomy continues. The sam: is true regarding the earth's atmosphere, and a lthoug_h considerably more is known regarding the natural laws whJCh govern the sea of air around the earth, there are many aspects of meteor- that are not yet fully understood. It is not unusual for the mind to become confused by unusual astronoinical and meteor ological conditions transmitted to it by the eye. Thus, the sky has been the setting for many strange sights which were not readily understood. Under certain weather conditions, r eflection and refraction processes can transform conventional aircraft, automobile lights, planets, meteors, and other identifiable fi~res i~to UFOs of many shapes and colors. Clouds, haze, mdustnal smoke, water droplets and ice particles in the atmosphere are typical ingredients which make up atmospheric lenses through which many illusions of flying objects a r e seen. Car lights reflecting on clouds can create luminous disks which da1t er- ratically through the sky at terrific speeds. Other light sources can produce similar illusions with appropriate variations, many of which even have specific color s pr ovided by refraction of the light through water and ice pa1ticles in the atmospher e. One of the most common causes for optical illusions of dis- torted and displaced objects is t he mirage. The index of refrac- tion of the atmosphere varies in the vertical, causing radio and light rays to bend. The prime contributor to index of r e- fraction variability is the temperature variation in the vertical. However, for radio waves, water vapor pressure (humidity) changes are also contributory. or radio or radar, the ray paths are assumed to be straight lines over an earth whose radius is % the tlue earth's radius under standard atmospheric conditions. This means the radio horizon is farther from the observer than it would be if the rays traveled in straight lines over the true earth. FIGURE 4: Refractive e ffects. Light rays follow the same kind of curved path as do radio rays, except that the moisture variations do not contribute to the bending. T o an observer or to a radar antenna, the apparent path of the ray is a straight line tangent to the curved path, as in Figure 4. This means an object seen over the true horizon may appear to "float" above the earth. Furthermore, if the object has much vertical structure such that rays travel differ- ent paths to the top of the object and to the bottom of the object, the differences in curvature of the top and bottom ray paths may cause a vertical distortion of the true height of the obj ect. One can pursue this subject in atmospheric optics under the phenomena known as "looming." Refractional Dispersion Combined refraction and dispersion of the earth's atmo- sphere can cause a celestial body to appear to be at a different location in space an