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Documents on the U.S. Atomic Energy Detection System [AEDS]

By William Burr

National Security Archive Electronic Briefing Book No. 7

For more information contact:
William Burr 202/994-7000 or nsarchiv@gwu.edu

Washington, D.C. – In August 1948, the U.S. Air Force created the Office of Atomic Energy-1 [AFOAT-1], giving it responsibility for managing the Atomic Energy Detection System [AEDS] discovering foreign atomic tests and other nuclear-weapons related activities. AFOAT/1 [later renamed the Air Force Technical Applications Center, or AFTAC] soon had an early triumph--the discovery of the first Soviet atomic test in 1949. For many years, AFOAT-1/AFTAC operated under the veil of secrecy; in 1949 no one without a high security clearance and only those with a clear "need to know" were aware that it was AFOAT-1 that had detected the Soviet test. It was not until 1975 that the Air Force even admitted that AFTAC had responsibility for operating the AEDS.

AFTAC has begun to operate somewhat more openly in recent years. For example, in the fall of 1997--the 50th anniversary of Army Chief of Staff's Dwight Eisenhower's order that the Air Force create a long-range detection system--the AFTAC Monitor published a twenty-four page history of the AEDS's first fifty years1. Nevertheless, much remains secret about AFTAC's history; with the support of Air Force lawyers, AFTAC has adamantly refused to declassify an official history of the first six years of its operation. It cannot, however, keep all its secrets. Other federal agencies have released documentation on AFOAT/1- AFTAC to the National Archives allowing researchers to trace in some detail the early history of long-range detection. Moreover, an extraordinary study by two Brandeis University anthropologists, Charles A. Ziegler and David Jacobson, Spying Without Spies: Origin of America's Secret Nuclear Intelligence Surveillance System (Praeger, 1995) provides the first history of first years of AFOAT/1 and the detection of the Soviet Union's first atomic test on 30 August.

During the early years of its efforts, AFOAT/1 developed and deployed a variety of detection systems--including acoustic, seismic, and radiological--to discover nuclear tests and monitor foreign nuclear activities generally, such as the production of fissile materials, plutonium and enriched uranium. Radiological detection systems--air sampling flights conducted by the Air Weather Service out of Alaska and the Navy's collection and analysis of rain water ("Operation Rainbarrel")-identified "Joe-1" while acoustic records helped AFOAT-1 determine that the test occurred in the Soviet Union (although it ranked the actual site of the test, at Semipaltinsk, as an area of lesser probability). AFOAT/1's efforts to enlarge its budget had met bureaucratic resistance, but after it broke the secrecy of the Soviet test the Air Force secured the resources it wanted to deploy a comprehensive acoustic/radiological/seismic "net" to detect foreign atomic activities.

During the 1950s and 1960s, AFOAT-1 perfected and expanded its detection system so it could monitor not only Soviet but also Chinese, British and French tests in the Asian-Pacific region. Moreover, during the 1960s, the National Reconnaissance Office became an important component of AEDS because overhead satellite photography made it possible to spot on-the-ground preparations for nuclear weapons tests. Thus, owing in part to photographs of Lop Nor, Secretary of State Dean Rusk could announce the October 1964 Chinese atomic test several weeks before it took place. Except for a few scattered document releases, however, the role of satellite photography in test detection is undocumented.

The possibility of not only detecting but also forecasting nuclear tests raised expectations that AFTAC and the intelligence community could not always meet. Indeed, AFTAC's fiftieth anniversary year marked the year of a major debacle of nuclear test prediction, the failure to estimate in advance the Indian nuclear test series in May 1998. The Central Intelligence Agency took the heat because its analysts had missed signals of impending Indian nuclear tests, making it impossible for U.S. officials to warn New Delhi of the repercussions. AFTAC, however, did its job; its seismic monitoring stations detected the Indian as well as the Pakistani tests as they occurred.

The documents that follow represent a sampling of the documentation on AFOAT-1/AFTAC that have been released at the National Archives. They shed light on U.S. nuclear detection during the 1950s and 1960s, the techniques used to monitor overseas nuclear activities, the limits of technical means, and the political problems associated with monitoring activities. Nevertheless, these documents only provide a glimmer of the U.S.'s long-range detection system. For example, the relationship between AFOAT-1/AFTAC and the intelligence agencies remains largely undocumented and data collected by AFOAT/1 detection systems and later processed and analyzed by CIA and other agencies is seldom declassified. Thus, CIA has held back the estimates of the Soviet atomic weapons stockpile that it included in National Intelligence Estimates. Although CIA and AFTAC are unlikely to change their generally restrictive policies, such an approach becomes less credible as more time elapses from the early years of long-range detection.



Document 1: Memorandum by R. C. Maude and D.L. Northrup, AFOAT/1, for Mr. Robert LeBaron, Deputy to the Secretary of Defense for Atomic Energy, "Notes on Technical Cooperation with British and Canadians in the Field of Atomic Energy Intelligence", 21 March 1951

Source: Records of U.S. Advisory Committee on Human Radiation Experiments.

AFOAT-1 was not only charged with detecting tests; it was also responsible for tracking other kinds of nuclear weapons activities, such as the production of fissile materials. This document describes one of the main technical means that AFOAT/1 and the Atomic Energy Commission [AEC] developed to track Soviet production of plutonium and the growth of the Soviet nuclear stockpile: the measurement of krypton-85 gas in the atmosphere. As this document suggests, one problem in using this technique was determining the contribution of foreign, non-Soviet, plutonium production to the total quantity of krypton-85 gas. Although exchanging information with the British and Canadians was possible, the development of the French nuclear program, among others, would pose new complications. The top secret classification of this document indicates that knowledge of the krypton-85 measurement effort was a highly sensitive nuclear intelligence technique. One of the signators of this report, Doyle Northrup, played a lead role in the early history of AFOAT/1. Originally a researcher with the Naval Ordnance Laboratory, he joined AFOAT/1 at its creation and became its deputy chief for science. Northrup participated in the analysis of the airborne-debris produced by "Joe I" and later co-authored the still-classified histories of atomic test detection.


Document 2: Charles P. Boner, Chairman, Joint Panel on IO-7, U.S. Department of Defense Research and Development Board to Chairmen, RDB Committees on Atomic Energy and Geophysics and Geography, "Review of DOD Program for Long Range Detection of Atomic Operations", 1 July 1951

Source: National Archives, Record Group 330, U.S. Department of Defense, Research and Development Board, Entry 341, box 435, RBD- AE Long-Range Detection 100.

Established under the 1947 National Security Act, the Defense Department's Research and Development Board was responsible for ensuring optimum coordination (and avoiding unnecessary duplication) in the military service's scientific R&D effort. Under the Board's Master Plan, IO stood for Intelligence Planning and Operations; IO-7 signified "Long-Range Detection of Foreign Atomic Explosions." Charles Boner, a University of Texas physicist and an expert on acoustics, chaired the joint panel on IO-7.

This document provides a useful survey of the principal methods for detecting nuclear weapons tests that Defense Department scientists had discovered by the early 1950s. Although the radiochemical methods that had detected the first Soviet tests had great value, they could not ascertain the location of a test; further development of the acoustical method was important for determining location (and presumably the time) of a nuclear test. This document also indicated some of the difficulties associated with the krypton-85 technique, e.g., lack of knowledge of krypton-85's distribution in the atmosphere, but also the high priority associated with this method and the determination to develop capabilities to locate Soviet atomic production facilities.


Document 3: Athelstan Spilhaus, Acting Chairman, Panel on IO-7 to Chief, AFOAT/1, "Review of Dogface Data," 3 October 1951, with enclosure.

Source: National Archives, Record Group 330, U.S. Department of Defense, Research and Development Board, box 435, RBD-AE Long- Range Detection 100.

The Soviets learned about AFOAT-1's capabilities through their British embassy agent, Kim Philby, in 1949, but they could not conceal atmospheric tests and U.S. intelligence continued to monitor them. The document that follows is an evaluation by the Research and Development Board's IO-7 panel on data collected on "Joe 2" (here codenamed "Dogface"), the Soviet Union's second atomic weapons test. It provides a glimpse in the capabilities of AFOAT/1's detection network, which identified the test as that of another implosion weapon like "Joe 1." Yet, while the preliminary results were off by a day--the test was on 25 September--and missed the presence of uranium-235 in the weapon, AFOAT-1's acoustical network produced a more precise estimate of the test location. Although the report does not identify Semipalitinsk, 48 N Lat, 80 E Long is very close to the former Soviet Union's nuclear test site.

The signator, Athelstan Spilhaus, was a geophysicist at the University of Minnesota. During the 1940s, he had been on the faculty at New York University where he had worked on "Project Mogul," an early attempt to use high-altitude balloons carrying acoustical instruments for long-range detection of atomic tests. Secretive tests of balloons in New Mexico for Project Mogul contributed to the UFO myths propagated after 1947.


Document 4: Memorandum of Conversation at Joint Staff Conference Room, Department of National Defense, Ottawa, "Technical Problems of Nuclear Test Limitation and Registration", 30 April 1957. Prepared by Chadwick Johnson, U.S. Department of State, Office of Special Assistant to the Secretary for Atomic Energy and Disarmament.

Source: National Archives, Record Group 59, U.S. Department of State, Decimal Files 1955-59, 600.0012/4-3057, released in response to National Security Archive Freedom of Information request.

This document records a conversation that occurred when the United States, the Soviet Union, and other governments were undertaking disarmament negotiations in London. During the negotiations the Soviet and British delegations raised the possibility of a comprehensive ban on nuclear weapons tests, but the U.S. government insisted on relatively tough conditions for a ban, mainly because it wanted to continue tests to develop "improved weapons." Moreover, U.S. officials indicated reluctance to support limitations on nuclear testing because of the difficulties in verifying an agreement.

In this document, an interagency team briefed Canadian government representatives on the capabilities and limitations of AFOAT/1's detection network. Among the limits were problems in detecting tests at high altitudes or in highly seismic areas, or were otherwise "carefully staged" so to avoid scrutiny. Moreover, AFOAT/1 found it difficult to measure nuclear tests yields with any degree of precision. Rather, "accuracies of intelligence estimates normally carry a reliability of a factor of two." In spite of its shortcomings, U.S. representatives observed that the detection system was "certainly capable of detecting important shots in certain areas of the world and would force the Soviets into elaborate efforts to avoid detection."


Document 5: Telegram No. TOCAH 14 from U.S. Department of State to U.S. Embassy Paris, 17 May 1960

Source: National Archives, Source: National Archives, Record Group 59, U.S. Department of State, Decimal Files 1960-1963, 761.5411/5-1760.

This message was sent to Secretary of State Christian Herter while he was with President Eisenhower at the ill-fated Paris summit. The downing of a U.S. U-2 over the Soviet Union on 1 May 1960 had led NASA to halt most U-2 flights as part of its cover story that a high-altitude plane used for weather monitoring had gone off-course over Soviet territory and that oxygen equipment needed to be checked. While Eisenhower had announced that the U.S. had suspended U-2 photographic surveillance flights over Soviet territory, other agencies were resuming U-2 flights for various purposes, such as AFTAC's air sampling projects, disguised as "weather research". As document 13 indicates, the purpose of "Project Crowflight"--a high altitude, air sampling activity--was to measure gases emitted during the production of plutonium.


Document 6: Memorandum from Richard St. F. Post, U.S. State Department Bureau of African Affairs, Office of North African Affairs, to William Witman II, Director, Office of North African Affairs, "Coverage of French Underground Tests," 4 August 1961, and letter from Howard Furnas, Acting Special Assistant to the Secretary for Atomic Energy and Outer Space, to General J. F. Rosenhauser, Chief, Air Force Technical Applications Center, 15 August 1961

Source: National Archives, Record Group 59, U.S. Department of State, Records of Special Assistant to Secretary for Atomic Energy and Outer Space, Subject and Country Files, 1950-1962, Box 5, file: 1961-France-Testing.

Although AFTAC operated in secrecy, much of its monitoring activities took place with the informed consent of host governments. Department of State files at the National Archives contain detailed accounts of formerly confidential initiatives to ensure the cooperation of many governments from which U.S. military technicians would run acoustic, seismic, and radiological monitoring systems. Nevertheless, State Department and other agency officials sometimes found it inadvisable to inform host governments. These documents record the hatching of a proposal to monitor secretly, from Libyan territory, French nuclear tests in Algeria. Whether AFTAC actually went through with this scheme remains to be discovered.


Document 7: Memorandum from Col. Frank Griffith, Deputy Chief, Air Force Technical Applications Center, to Special Assistant for Atomic Energy and Outer Space, "B/20-4 System Expansion", 4 January 1962

Source: National Archives, Record Group 59, U.S. Department of State, Decimal Files 1960-1963, 700.5611/1-462.

Not all governments were willing to harbor the U.S.'s nuclear detection facilities either because they were officially neutral in the Cold War or they did not want to face domestic or Soviet bloc criticism for cooperating in this area. Some AEDS projects took up so little space, however, that the U.S. government could operate the applicable equipment at embassies or consular offices whether or not the host government had approved. This document shows how such circumvention became possible. The B/20-4 "heat exchangers", the size of a refrigerator, could be used to measure levels of "rare gases" (e.g., krypton-85) and refine estimates of world-wide plutonium production. The B/20-4 described in this document may be related to the technology developed by the Air Reduction Sales Company and described in Ziegler and Jacobson's Spying Without Spies.


Document 8: State Department Circular Telegram 1444 to Various Embassies, "Project Clear Sky," 6 February 1964

Source: National Archives, Record Group 59, U.S. Department of State, Central Foreign Policy Files, 1964-1966, file DEF 18-8 US.

During the 1960s the AEDS was expanded after the United States ratified the 1963 limited nuclear test ban treaty. Verifying that treaty signatories were complying with its terms became a critical issue because the Kennedy administration had assured a critical U.S. Senate that it would "effectively police" the ban on atmospheric and oceanic nuclear tests. Under "Project Clear Sky," the Johnson administration expanded AEDS although not always with the consent of host governments. One step that the Defense Department began taking was the deployment of "ground filter units," the B/20-4 system described above, at specific U.S. embassies. By collecting tiny airborne particles from nuclear tests, the GFUs could help Washington determine if a nuclear weapons test had recently occurred as well as draw inferences about its characteristics (design, yield, composition)


Document 9: State Department Telegram to Various Addressees, "Project Clear Sky", 16 October 1964

Source: National Archives, Record Group 59, U.S. Department of State, Central Foreign Policy Files, 1964-1966, file DEF 18-8 US.

Having already learned about the first Chinese atomic test that same day, the U.S. government wanted to be able to monitor carefully any tests that might follow. The State Department asked several embassies in South Asia and the Far East to seek "standing permission" for the use of specified air bases and air space so that the U.S. Air Force could quickly conduct air sampling missions.


Document 10: U.S. Embassy Karachi Telegram 980 to State Department, 18 November 1964

Source: National Archives, Record Group 59, U.S. Department of State, Central Foreign Policy Files, 1964-1966, file DEF 18-8 US.

The government of Pakistan refused the U.S. request for access to air bases after the Chinese atomic test; this cable explains why. It has an almost unique status as one of the few declassified documents available describing a conversation between a foreign head of state and a senior CIA official. In this instance, the discussants were Mohammed Ayub, President of Pakistan, and James Critchfield, Chief of the CIA Directorate of Plan's South Asia Division accompanied by U.S. Ambassador Walter P. McConaughy (the Shaffer mentioned in the document was embassy attache John Shaffer, the CIA station chief). Arriving in Karachi a month after the first Chinese atomic test, Critchfield briefed Ayub on Chinese and Soviet nuclear capabilities and discussed recent regional and international developments, including Nikita Khrushchev's fall from power. Apparently concerned about his relations with Beijing but not too worried about Chinese nuclear capabilities, Ayub turned down the request for standing permission to conduct air sampling missions in Pakistan noting that "We cannot afford to make any more enemies." For Ayub, China's posture was essentially "defensive" and "their aggressive statements can be attributed to this attitude."


Document 11: State Department Airgram to U.S. Embassy, Buenos Aires, CA-3143, "Project QUICK DIP", 17 September 1965

Source: National Archives, Record Group 59, U.S. Department of State, Central Foreign Policy Files, 1964-1966, file DEF 18-8 US.

The subject of this airgram, "Quick Dip", was another one of AFTAC's efforts to determine the amount of "rare gases" in the atmosphere and measure plutonium production by the "Sino- Soviets". As in the 1960 project "Crowflight" described in document 5, the U.S. Air Force, using an Air Weather Service cover staged air sampling flights from an Argentine air base. The aircraft used in this activity were based in Kirtland Air Force Base, New Mexico, which had housed over the years important nuclear activities (e.g., weapons storage facilities and weapons training programs.)


Document 12: State Department Airgram to U.S. Embassy Rome, CA-6065, "Project Clear Sky", 26 February 1968

Source: National Archives, Record Group 59, U.S. Department of State, Central Foreign Policy Files, 1967-1969, file DEF 18-8 US.

This message discloses AFTAC's plans to upgrade its nuclear test detection capabilities by using a new technological development. The means described, ionospheric detection, developed as a result of Over-the-Horizon Forward Scatter Radar, or 440-L radar, developed during the 1960s to detect missile launches from Chinese or Soviet territory. Not actually radar, 440L was a series of high frequency radio transmitters and receivers on either side of the Sino-Soviet landmass producing continuous signals which bounced between the ionosphere and the surface of the earth until reaching the receiving stations. Any disturbances in the pattern indicated missiles penetrating the ionosphere. As this airgram suggests, because atmospheric nuclear tests influenced the signals produced by 440L transmitters, AFTAC quickly added forward scatter to its bag of nuclear detection techniques.

As the U.S. Air Force had established a 440L site at Aviano Air Base in Italy, AFTAC wanted to co-locate additional equipment there to upgrade its capabilities. When employed jointly, equipment used for detecting low frequency phase anomaly, atmospheric fluorescence, and changes in the magnetic field would make the ionospheric detection network "more effective." AFTAC, however, could not deploy 440L technology unnoticed and would have to conduct special surveys to identify the most suitable area.



1. See Mary Welch, "AFTAC Celebrates 50 Years of Long Range Detection", AFTAC Monitor: Oct. 1997 (pp. 8-32).


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