CIA U-2 Collection of Signals Intelligence, 1956-1960

CIA U-2 Collection of Signals Intelligence, 1956-1960

By James E. David*

Washington, D.C., March 8, 2022 – Central Intelligence Agency (CIA) U-2 reconnaissance aircraft flew more than 250 overflight and peripheral missions in Europe, the USSR, Mideast, and the Far East from June 1956 through 1959.  Photographic intelligence was the program’s primary objective, and the planes carried one of a series of increasingly capable cameras.  Both the films and much of the intelligence derived therefrom have been declassified and covered in the open literature.[1]

Much less well-known is that the secondary objective was signals intelligence (SIGINT), which included electronic intelligence (ELINT) and communications intelligence (COMINT).  On every mission during the 1950s, CIA U-2s carried one or more SIGINT sensors.  The two sensors initially flown had limited capabilities.  But the CIA developed more sophisticated ones quickly. 

Unfortunately, only a small number of documents on the SIGINT effort have been declassified.  They disclose the technical details of the sensors, the dates of service, the targets in general, the raw intelligence acquired on selected missions, and some other limited information. However, the vast majority of data on the intelligence collected and its contributions to satisfying ELINT and COMINT requirements remains classified.  Not surprisingly, there is little treatment of the early CIA U-2 SIGINT efforts in the open literature. 

To help fill the gap, this Electronic Briefing Book presents much of what is known about the SIGINT operations.  It is long past the time that the CIA, National Security Agency, and other organizations re-review the records previously released in part and the numerous records withheld in their entirety to enable more of this important story to be told.

President Dwight D. Eisenhower approved the joint CIA-Air Force proposal to build the high-altitude U-2 reconnaissance aircraft in November 1954.  Officials believed that its operating altitude of 70,000 feet, far higher than any other reconnaissance aircraft, would make it invulnerable to detection by Soviet air defense radars for several years and successful attack for a somewhat longer period [Documents 1 and 2].[2]

This protection would enable the U-2 to conduct overflights of the Soviet Union and help fill critical intelligence gaps.  The most significant shortfalls concerned the long-range bomber force, nuclear weapons program, ballistic missile program, and the air defense system [Document 3].[3]   

Officials soon created the AQUATONE special security control system to cover the existence of the program and its research and development, testing, staging, security, operations, and other details [Document 4].  AQUATONE was replaced by CHALICE in 1958.  The officials also established the TALENT special security control system to cover the raw and finished intelligence from the program.[4]

The U-2’s primary mission was photographic intelligence.  Three new cameras – the A-1, A-2, and B - were developed for the U-2.  All were more capable than any existing aerial cameras.  Because of its superior performance, the B camera was the only one used from late 1958 on.  Photographic targets included military airfields, aircraft manufacturing plants, missile testing and deployment complexes, missile manufacturing facilities, radar sites, naval bases and shipyards, ground forces installations, communication sites, and nuclear production, storage, and testing facilities.  This imagery was essential to accurately assess Soviet offensive and defensive capabilities and determine the targets to be attacked in case of war.[5]  

Air Force and Navy reconnaissance aircraft flew hundreds of peripheral missions with cameras annually by the mid-1950s, but they of course did not acquire photography of the vast interior.  The Air Force (and to a lesser extent, the Navy) had also started conducting overflights in the late 1940s to collect imagery.  However, they were limited in number and coverage because the aircraft flew at lower altitudes, were vulnerable to Soviet air defenses, and did not have the range to fly deep-penetration missions.  Additionally, the Soviets frequently lodged strong protests and every flight risked creating an international incident.  Because of these factors and the impending onset of U-2 overflights, military overflights essentially ended after May 1956.[6]                   

The U-2’s secondary mission was SIGINT to acquire ELINT or COMINT.  During the 1950s, ELINT included the interception of a wide range of radars and processing and analyzing the intercepts to determine their location and technical characteristics such as frequencies, modulation, and pulse repetition rate.  These included early warning radars that determined the distance and direction of aircraft, height finding radars that determined their altitude, ground control intercept radars that directed fighters, and fire control radars that guided the firing of surface-to-air missiles and anti-aircraft artillery.  The ELINT intelligence was incorporated into Radar-Order-of-Battle and Electronic-Order-of-Battle reports, which were used to plan the safest ingress and egress routes for combat aircraft penetrating the USSR and to develop electronic countermeasures.[7] 

          All Soviet radars during the latter part of the 1950s utilized frequencies above the high frequency range.  The majority employed frequencies in the very high frequency range.  Others were designated S-band radars that operated in the upper part of the ultra-high or lower part of the super high frequency ranges.  There was also one L-band radar that used the lower part of the ultra-high frequency range.  The propagation characteristics of these above high frequencies required in almost every case that the ELINT sensor be in the line of sight of the radars to acquire intercepts.  Except in the cases of airborne and shipborne radars, aircraft were the only platform that could effectively perform this mission.  Many Air Force and Navy reconnaissance aircraft conducting peripheral reconnaissance flights intercepted radars located at or near the borders but not from the vast interior of the USSR.[8]            

Electronic intelligence also included the interception and processing of telemetry downlinked by missiles to ground stations during test flights.  Telemetry is the measurement of variables such as temperatures, acceleration, vibrations, and propellant levels.  Technical personnel of the country conducting the test used it in monitoring the vehicles before launch and during flight and thereby determined which systems and components worked well and which did not and why.  For the United States, analysis of the data was essential to determining the performance characteristics of the missiles, such as the type of propulsion and guidance systems, range, and payload capacity.  Because the Soviets used above high frequencies for telemetry, ELINT sensors at ground stations or on ships and aircraft had to be in the line of sight of the missile to intercept it.[9]   

Human sources in the late 1940s began providing intelligence on the Soviets’ only missile testing complex – Kapustin Yar, about 100 miles east of Stalingrad – and the short- and medium-range missile tests there.  The missiles flew eastward and impacted in one of several areas.  During the early 1950s, COMINT started furnishing additional intelligence including intercepts of lengthy pre-launch countdowns (although analysts could not initially distinguish between practice and actual countdowns), communications of transport flights in and out of Kapustin Yar and communications between Kapustin Yar and the downrange stations.  The COMINT was acquired by ground stations operated by the three service cryptologic agencies – Air Force Security Service, Army Security Agency, and Naval Security Group – in Turkey and likely other countries.[10]    

The Army Security Agency’s ground station at Sinop, Turkey, collected the first telemetry intercept (from a SS-1 short-range missile) in June 1956.   The Air Force Security Service soon started acquiring telemetry from missiles launched at Kapustin Yar at its ground station at Samsun, Turkey.  It also built a specialized radar at Diyarbakir, Turkey, during 1955 to detect and track missiles launched from the complex.  Although the details remain classified, it appears that Air Force RB-57Ds and Navy P4M Mercators and A3D Skywarriors targeted telemetry from missiles launched at Kapustin Yar.  From mid-1953 to September 1957, radar intelligence and COMINT identified at least 275 launches from the complex to ranges of about 75, 150, 300, 650, and 950 nautical miles.  These sources continued identifying numerous tests in the following years.  Although it is unknown what platforms obtained them, 18 intercepts were acquired in 1956 and increasing numbers in the following years.  Undoubtedly based on these intercepts, along with radar intelligence and ground photography of selected missiles during the November 1957 Moscow parade, by late 1959 the intelligence agencies had determined with varying degrees of certainty the ranges, guidance systems, accuracy, warhead weights and types, configurations, and propulsion systems of the five short- and medium-range ballistic missiles tested at Kapustin Yar.[11]   

Communications intelligence collected by ground stations at various locations beginning in 1955 suggested the construction of additional suspected missile program installations near Novokazalinsk/Dzhusaly in the Kazakh SSR (eventually designated Tyuratam) and at Klyuchi on the Kamchatka Peninsula.  By early 1957, additional but still limited COMINT enabled intelligence agencies to identify the former as a possible launch complex for intercontinental ballistic missiles (ICBMs) and satellites and the latter as the terminus of the range for ICBM tests.  Two U-2 missions in August 1957 provided the first photography of Tyuratam and confirmed it was a launch site with one completed launch pad and several others under construction.  (Tyuratam also served in the early years as the launch facility for all Soviet space shots.)  U-2 photography of Klyuchi in June and September 1957 revealed that it was the terminus for ICBM tests.[12] 

The few declassified records available demonstrate that the United States had only limited intelligence on activities at Tyuratam during 1957.  Evidence of the first ICBM test in August 1957 came from a Soviet press release and the second test the following month from comments made to a French politician by Soviet leader Nikita Khrushchev.  Confirmation that Sputnik I in October 1957 and Sputnik II the following month were in orbit came from Soviet press releases after their launches and reports of various commercial and government receiving stations hearing the signals transmitted by them.[13]  

The intelligence agencies undertook a massive effort to close the information gap on the Soviet ICBM and space programs, but most of the details remain classified.  They took steps to improve COMINT coverage of activities on the Tyuratam range.  The Air Force Security Service ground stations at Trabzon, Turkey; Wakkanai, Japan; and Peshawar, Pakistan were soon equipped to acquire telemetry from vehicles launched at Tyuratam.  In 1958, the Army Security Agency established a ground station at Shemya in the western Aleutians to collect telemetry from the ICBMs and, after separation, the reentry vehicles during the terminal phase of their flights.  The Air Force Security Service soon installed a radar at the site to track the missiles and reentry vehicles during this period.  The CIA began operating a ground station in northern Iran in 1959 to acquire telemetry from vehicles launched at Tyuratam.  Air Force planes and CIA U-2s conducted peripheral flights along the Soviet borders with Iran and Afghanistan to obtain telemetry intercepts.  Around Kamchatka Peninsula and the Pacific Ocean impact area (which the Soviets used in some tests beginning in the fall of 1959), Navy P4M Mercators, A3D Skywarriors, and possibly Air Force planes collected telemetry from ICBMs and, after separation, their reentry vehicles.  From August 1957 through the end of 1959, the Soviets tested at least 17 ICBMs (not all successfully).  Although it is unknown except in one case what platforms obtained them, four intercepts were acquired in 1958 and 17 the following year.  Undoubtedly based on them and radar intelligence, by late 1959 the intelligence agencies had estimated the probable range, propulsion system, configuration, guidance system, accuracy, type of nosecone, and warhead weight of the only ICBM tested to date.[14]   

Officials believed at the beginning of the project that the U-2 could also possibly perform COMINT.  For many decades, the USSR and every other nation in the world used high frequency systems for most communications.  The skywaves bounced off the ionosphere and back to Earth repeatedly, enabling interception to take place thousands of miles away by ground stations and occasionally aircraft and ships. Because the worldwide network of ground stations provided good coverage of Soviet high frequency communications, U-2s targeted the ultra-high frequency communications the Soviets were increasingly using.[15]   Use of these ranges required that the COMINT sensor be in line of sight of the transmitter to acquire intercepts.  Unless the transmitter was on or near the borders, aircraft were the only platform capable of collecting them. 

Selected Soviet ground-to-air and air-to-ground communications in the Far East began transitioning from high frequency to ultra-high frequencies late in the Korean War.  The Air Force quickly started an intercept program using a single aircraft.  Ground-to-air and air-to-ground communications in other parts of the USSR moved to ultra-high frequencies later in the decade.  The Air Force expanded the collection program and began routinely flying the aircraft on peripheral reconnaissance missions to acquire intercepts from the border areas.  The Soviets were also starting to employ ultra-high frequency microwave systems for medium- and long-distance communications.  These utilized towers spaced approximately 25 to 30 miles apart to receive the signals and relay them to the next tower.  Since most of these systems operated in the interior of the USSR, only aircraft conducting overflights could intercept them.[16] 

The CIA developed new ELINT sensors for the U-2.  The first, System I, primarily intercepted S-band radars and flew on every mission from 1956-1959.  Three larger and more capable receivers that intercepted a wider range of radars and telemetry – Systems IV, V, and VI – entered service later.  System IV was carried on 17 missions from 1957-1959, System V on three in 1956-1957, and System VI on three in 1957-1958.  While Systems IV and V displaced the main camera, System VI did not.  Although there are few declassified records on the individual targets and the intelligence acquired, it is widely reported that the sensors provided valuable information.  A dedicated COMINT sensor, System III, intercepted selected very high frequencies.  It flew on many missions in 1956-1958 but proved ineffective.  System VII was designed to acquire telemetry and achieved some success during 23 missions during 1959-1960.  As did Systems IV and V, it also displaced the main camera.[17]   

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* James E. David is curator of national security space programs at the Smithsonian National Air & Space Museum.