The Origins of Aerial Reconnaissance II


Frederick Sidney Cotton

Alarmed by the rise of Adolf Hitler and the advent of the Luftwaffe, the Royal Air Force pioneered covert, peacetime aerial reconnaissance in the late 1930s. British Squadron Leader Fred W. Winterbotham of the Air Ministry successfully convinced British and French officials of the need to reconnoiter German military installations. Eventually, Winterbotham contacted Frederick Sydney Cotton, an Australian pilot with extensive aerial photography and World War I experience. They procured a Lockheed L12A, a twin-engine plane similar to one made famous by Amelia Earhart’s ill-fated last flight. Beginning in March 1939, Cotton flew 15 overflight missions over targets in Germany, Italy, and the Mediterranean, including a flight to photograph German naval vessels in Wilhelmshaven on 1 September 1939. Winterbotham captured Cotton’s experiences in an August 1939 memorandum titled “Photographic Reconnaissance of Enemy Territory in War.” Summarizing the lessons, Cotton maintained, “The best method appears to be the use of a single small machine, relying on its speed, climb, and ceiling to avoid destruction. A machine such as a single-seat fighter could fly high enough to be well above Ack-Ack fire and could rely upon sheer speed and height to get away from the enemy fighters. It would have no use for armament or radio and these could be removed to provide room for extra fuel, in order to get the necessary range. It would be a very small machine painted so as to reduce its visibility against the sky.”

World War II provided a test for airpower theory as well as technology. Early British efforts at strategic bombing revealed that the bomber would not always get through. From the initial RAF sorties against Wilhelmshaven in 1939 to the fall of France in 1940, British bomber raids suffered unacceptable losses to German fighter defenses. Well-armed, high-performance fighters refuted the assumption of bomber omnipotence. In response, the RAF developed a doctrine of night area bombardment that recognized operational limits. Because existing technology could not provide accuracy suitable for precision bombing at night, the RAF Bomber Command emphasized attacks on German cities- crushing morale and destroying the homes of the enemy’s industrial workforce. Area bombing as practiced by Air Marshal Sir Arthur T. Harris, commander of the RAF Bomber Command, resisted the appeal of selective, or “panacea,” targets. Incapable of pinpoint bombing, RAF area strikes also required less precise intelligence.

The European air war also demonstrated the difficulty of conducting aerial reconnaissance. At the beginning of the war, confidence in existing reconnaissance procedures vanished when photoreconnaissance Bristol Blenheim aircraft were shot down at alarming rates. Additionally, the valiant efforts of surviving pilots were thwarted by frozen cameras, fogged lenses, and cracked film. These dismal results forced the British Air Ministry to revamp reconnaissance methods.

Despite initial failures, the RAF created the concepts, equipment, and tactics of modern strategic photographic intelligence. Now an RAF officer, Frederick Sidney Cotton added to his civilian photographic expertise. During the first two years of the war, Cotton’s exploits with a stripped-down polished Supermarine Spitfire assumed legendary proportions as he gained information unobtainable by other sources. Moreover, technicians at the RAF’s Photographic Reconnaissance Unit developed high-altitude cameras-one with a 36-inch focal length that produced high-quality photographs with clear resolution. Equally important, the British Air Ministry recruited talented, highly motivated individuals from a broad range of civilian occupations to serve as photographic interpreters. By refining the equipment, techniques, and methodology of this seemingly mundane field, the RAF furthered the processing and analyzing of data gathered by reconnaissance crews. Finally, the British understood the importance of centralization and coordination of intelligence data. Efforts to streamline the processing of intelligence information furthered the proper analysis of data and the use of information by field commanders.

The entry of the United States Army Air Force (USAAF) into the European air war proved the inadequacy of prewar reconnaissance concepts and training. After a poor showing in the initial phase of North African operations, the Army Air Forces (AAF) reorganized observation units along the lines of RAF tactical reconnaissance. Like their British counterparts, Americans learned from bitter experience the value of aircraft with altitude, speed, and range characteristics superior to enemy interceptors. The lack of aircraft specifically designed for aerial reconnaissance plagued American reconnaissance efforts. Eventually, the AAF paralleled British efforts when American pilots flew modified Lockheed P-38 Lightnings and North American P-51 Mustangs to support the AAF’s daylight strategic bombardment campaign. The German introduction of Messerschmitt Me-262 jet fighters during the latter stages of the war menaced Allied photoreconnaissance aircraft. Fortunately, the Allies possessed an overwhelming numerical advantage that allowed the Combined Bomber Offensive to continue. Although American reconnaissance groups performed valiantly, they added little to RAF photoreconnaissance concepts.

Apart from British advances in strategic photographic intelligence, RAF performance in the Battle of Britain demonstrated the capability of aerial defense. Combining communications intelligence with new radar technology, by 1940 the RAF had developed a practical network of early warning and ground-controlled intercept (GCI) stations. These stations notified fighter bases of the approach of enemy aircraft and directed fighters to intercept the enemy. Although many factors contributed to the defeat of the Luftwaffe in the Battle of Britain, British technology played a vital role. Using radar, the British were able to refute earlier assumptions that bombers could attack without warning. By the summer of 1940, the Germans introduced a radio-aided navigational device, known as Knickebein, to improve night bombing accuracy. British efforts to counter it resulted in the “Battle of the Beams.” By the winter of 1943, electronic warfare played a critical role in RAF night bombing. In support of their night area bombing campaign, the British developed navigational aids (including Gee and Oboe), H2S airborne radar, and radar countermeasures (WINDOW, or chaff, and various electronic devices). The Germans countered with night fighters, SN2 airborne intercept (AI) radar, and a variety of passive radar detection devices. The combination of a German technological breakthrough and innovative night-fighter tactics caused major RAF losses in the Battle of Berlin (November 1943-March 1944) and almost defeated the RAF night bombing campaign. These events emphasized the growing importance of electronic warfare during World War II. Combatants now needed information about the enemy’s electronic defenses in order to plan successful strikes.

Although Germany and Britain played the leading role in developing electronic warfare, the United States contributed in the specialized field of airborne electronic intelligence (ELINT). While the RAF introduced ELINT-equipped Wellington bombers in 1942, the United States assumed the lead in electronic reconnaissance with the introduction of specialized electronic reconnaissance aircraft (nicknamed “Ferret”) in 1943. To accomplish this feat, the United States mobilized scientific talent and harnessed the production capacity of its vast electronics industry. The Office of Scientific Research and Development, the heart of the American electronic warfare effort, selected Dr. Frederick E. Terman from Stanford University to head the Radio Research Laboratory (RRL), which was responsible for radio and radar countermeasures (RCM). In a shrewd organizational move, the National Defense Research Committee kept Terman’s Division 15 independent from Division 14, which was created to advance radar. Hence, there was no bureaucratic pressure from radar proponents to retard the development of radar countermeasures. Therefore, the RRL moved quickly to develop the components necessary for electronic reconnaissance and radar jamming. In early 1942, Terman directed the adaptation of SCR 587 radar intercept receivers for airborne use. This equipment allowed aircraft to identify enemy radar sites and to determine their operating characteristics. In addition to its role in developing electronic countermeasures, the United States offered tremendous production capability to the Allied electronic warfare effort. Dr. George Rappaport observed:

Once there was an operational requirement for it [the APR-2 Carpet jamming transmitter] the Army Air Force wanted 15,000 and I was sent to Delco at Kokomo, Indiana, to discuss the contract to mass produce [sic] it. Bert Schwarz, their brilliant chief production engineer, showed me around the plant. . . . As we walked around Bert looked rather unhappy and he kept scratching his head. In the end I said to him, “What’s wrong, can’t you build the 15,000 for us?” He paused for a while, then answered, “Well, 15,000 a week, that’s an awfully tough rate.” I looked at him in amazement and told him I did not want 15,000 Carpets per week, 15,000 in a year would do fine. Bert broke out into a smile. “Oh,” he said, “I’ll have to reduce my production capacity to do that!”

Before the United States could design and build jammers, the AAF needed to understand the performance characteristics of enemy radar. In early 1942, the USAAF established a radar school at Morrison Field, Florida, which moved to Boca Raton, Florida, in June 1942. The radar school developed an RCM course and trained specialists in radar detection (nicknamed “Ravens”) for air operations. Initially, training in antiquated Lockheed B-34 bombers, the Ravens operated radar search receivers and pulse analyzers to find radar transmissions and display them on oscilloscopes for analysis. In addition, the RCM school taught the rudiments of electronic jamming and the use of WINDOWS (also called chaff)-small strips of aluminum foil scattered from an aircraft that masked the aircraft’s image on a radarscope. Unfortunately, shortages of equipment and experience limited the school’s effectiveness. In the words of one participant, “The RCM course was a riot-nobody was sure how anything (equipment) worked, if it worked nobody really knew why, and if it did what it was supposed to accomplish.” Since the AAF acknowledged British expertise in the European theater, the first American Ravens headed for the Pacific.

On 6 March 1943, Lts Bill Praun and Ed Tietz flew the first American electronic reconnaissance flight against a Japanese radar on Kiska Island in the Aleutian Islands chain. Spotted by aerial photography, the Kiska radar afforded a unique opportunity to learn about Japanese equipment. Knowing few details, American electronic analysts assumed Japanese radar technology to be inferior. Consequently, “Ferret I,” a modified B-24D, conducted a series of flights with varied success. Praun and Tietz received signals in the 100-megacycle (mc) range that suggested a Japanese Mark I Model 1’s early warning radar, but the new APR-4 search receivers provided only crude data. Nevertheless, Ferret I blazed the trail for American electronic reconnaissance.



Flight No. 6 of Ferret III, 14–15 June 1943

With the Allied invasion of North Africa, the AAF broadened the scope of Ferret activity. In May 1943 Ferret III entered service with the 16th Reconnaissance Squadron. Later joined by Ferrets IV, V, and VI, the modified B-17s flew night, low level missions into Axis radar coverage. Initially concentrating on Sicily, the aircraft eventually flew electronic reconnaissance missions over Sardinia, Corsica, Italy, and southern France. Between May 1943 and September 1944, the Mediterranean Ferrets flew 184 sorties and discovered 450 enemy radar sites. As a result of Ferret data, analysts learned the range and operating frequencies of German Freya early warning radar, Gema coastal surveillance radar, and Würzburg GCI radar. This information aided operational planning for amphibious assaults Husky, Avalanche, Shingle, and Dragoon, as well as the strategic bombing missions conducted by the 15th Air Force. In addition, the 16th Reconnaissance Squadron determined that the new American RC-156 Carpet electronic jammer offered protection for bombers against gun-laying radar (now called fire-control radar). Finally, the ELINT B-17s improved new Ferret tactics. American electronic reconnaissance aircraft accompanied RAF Wellington night bombers and established collection orbits during raids. On other occasions, crews braved night missions flying 200-500 feet over mountains-a most “unhealthy” practice-to surprise German radar operators. The daring, often improvised, tactics of the 16th uncovered valuable information about enemy defensive systems. Thus, by fall 1944, AAF Ferrets added a new dimension to strategic aerial reconnaissance.

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