A bhangmeter is a non-imaging radiometer installed on reconnaissance and navigation satellites to detect atmospheric nuclear detonations and determine the yield of the nuclear weapon. [1] They are also installed on some armored fighting vehicles, in particular NBC reconnaissance vehicles, in order to help detect, localise and analyse tactical nuclear detonations. They are often used alongside pressure and sound sensors in this role in addition to standard radiation sensors. Some nuclear bunkers and military facilities may also be equipped with such sensors alongside seismic event detectors.
The bhangmeter was developed at Los Alamos National Laboratory by a team led by Herman Hoerlin. [2]
The bhangmeter was invented, and the first proof-of-concept device was built, in 1948 to measure the nuclear test detonations of Operation Sandstone. Prototype and production instruments were later built by EG&G, and the name "bhangmeter" was coined in 1950 by Frederick Reines. [3] Bhangmeters became standard instruments used to observe US nuclear tests. A Mod II bhangmeter was developed to observe the detonations of Operation Buster-Jangle (1951) and Operation Tumbler-Snapper (1952). [4] These tests lay the groundwork for a large deployment of nationwide North American bhangmeters with the Bomb Alarm System (1961-1967).
US president John F. Kennedy and the First Secretary of the Communist Party of the Soviet Union Nikita Khrushchev signed the Partial Test Ban Treaty on August 5, 1963, [5] under the condition that each party could use its own technical means to monitor the ban on nuclear testing in the atmosphere or in outer space. [6]
Bhangmeters were first installed, in 1961, aboard a modified US KC-135A aircraft monitoring the pre-announced Soviet test of Tsar Bomba. [7]
The Vela satellites were the first space-based observation devices jointly developed by the U.S. Air Force and the Atomic Energy Commission. The first generation of Vela satellites were not equipped with bhangmeters but with X-ray sensors to detect the intense single pulse of X-rays produced by a nuclear explosion. [8] The first satellites which incorporated bhangmeters were the Advanced Vela satellites.
Since 1980, bhangmeters have been included on US GPS navigation satellites. [9] [10] [11]
The silicon photodiode sensors are designed to detect the distinctive bright double pulse of visible light that is emitted from atmospheric nuclear weapons explosions. [2] This signature consists of a short and intense flash lasting around 1 millisecond, followed by a second much more prolonged and less intense emission of light taking a fraction of a second to several seconds to build up. [12] This signature, with a double intensity maximum, is characteristic of atmospheric nuclear explosions and is the result of the Earth's atmosphere becoming opaque to visible light and transparent again as the explosion's shock wave travels through it. [10]
The effect occurs because the surface of the early fireball is quickly overtaken by the expanding "case shock", the atmospheric shock wave composed of the ionised plasma of what was once the casing and other matter of the device. [13] Although it emits a considerable amount of light itself, it is opaque and prevents the far brighter fireball from shining through. The net result recorded is a decrease of the light visible from outer space as the shock wave expands, producing the first peak recorded by the bhangmeter.
As it expands, the shock wave cools off and becomes less opaque to the visible light produced by the inner fireball. The bhangmeter starts eventually to record an increase in visible light intensity. The expansion of the fireball leads to an increase of its surface area and consequently an increase of the amount of visible light radiated off to space. The fireball continues to cool down so the amount of light eventually starts to decrease, causing the second peak observed by the bhangmeter. The time between the first and second peaks can be used to determine its nuclear yield. [14]
The effect is unambiguous for explosions below about 30 kilometres (19 mi) altitude, but above this height a more ambiguous single pulse is produced. [15]
The name of the detector is a pun [3] which was bestowed upon it by Fred Reines, one of the scientists working on the project. The name is derived from the Hindi word "bhang", a locally grown variety of cannabis which is smoked or drunk to induce intoxicating effects, the joke being that one would have to be on drugs to believe the bhangmeter detectors would work properly. This is in contrast to a "bangmeter" one might associate with detection of nuclear explosions. [3]
Project Mogul was a top secret project by the US Army Air Forces involving microphones flown on high-altitude balloons, whose primary purpose was long-distance detection of sound waves generated by Soviet atomic bomb tests. The project was carried out from 1947 until early 1949. It was a classified portion of an unclassified project by New York University (NYU) atmospheric researchers. The project was moderately successful, but was very expensive and was superseded by a network of seismic detectors and air sampling for fallout, which were cheaper, more reliable, and easier to deploy and operate.
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Measurement and signature intelligence (MASINT) is a technical branch of intelligence gathering, which serves to detect, track, identify or describe the distinctive characteristics (signatures) of fixed or dynamic target sources. This often includes radar intelligence, acoustic intelligence, nuclear intelligence, and chemical and biological intelligence. MASINT is defined as scientific and technical intelligence derived from the analysis of data obtained from sensing instruments for the purpose of identifying any distinctive features associated with the source, emitter or sender, to facilitate the latter's measurement and identification.
Vela was the name of a group of satellites developed as the Vela Hotel element of Project Vela by the United States to detect nuclear detonations and monitor Soviet Union compliance with the 1963 Partial Test Ban Treaty.
Project Vela was a United States Department of Defense project to monitor Soviet Union compliance with the 1963 Partial Test Ban Treaty. The treaty banned the testing of nuclear weapons in the atmosphere, in outer space, and underwater, but permitted underground testing.
The Vela incident was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the South African territory of Prince Edward Islands in the Indian Ocean, roughly midway between Africa and Antarctica. Today, most independent researchers believe that the flash was caused by a nuclear explosion—an undeclared joint nuclear test carried out by South Africa and Israel.
The Air Force Technical Applications Center (AFTAC), based at Florida's Patrick Space Force Base, is an Air Force surveillance organization assigned to the Sixteenth Air Force. Its mission is to monitor nuclear treaties of all applicable signatory countries. This is accomplished using seismic, hydroacoustic and satellite-detection systems alongside ground based and airborne materials collection systems.
Stirling Auchincloss Colgate was an American nuclear physicist at the Los Alamos National Laboratory and a professor emeritus of physics at the New Mexico Institute of Mining and Technology from 1965 to 1974, of which he also served its president.
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Materials MASINT is one of the six major disciplines generally accepted to make up the field of Measurement and Signature Intelligence (MASINT), with due regard that the MASINT subdisciplines may overlap, and MASINT, in turn, is complementary to more traditional intelligence collection and analysis disciplines such as SIGINT and IMINT. MASINT encompasses intelligence gathering activities that bring together disparate elements that do not fit within the definitions of Signals Intelligence (SIGINT), Imagery Intelligence (IMINT), or Human Intelligence (HUMINT).
Nuclear MASINT is one of the six major subdisciplines generally accepted to make up Measurement and Signature Intelligence (MASINT), which covers measurement and characterization of information derived from nuclear radiation and other physical phenomena associated with nuclear weapons, reactors, processes, materials, devices, and facilities. Nuclear monitoring can be done remotely or during onsite inspections of nuclear facilities. Data exploitation results in characterization of nuclear weapons, reactors, and materials. A number of systems detect and monitor the world for nuclear explosions, as well as nuclear materials production.
Electro-optical MASINT is a subdiscipline of Measurement and Signature Intelligence, (MASINT) and refers to intelligence gathering activities which bring together disparate elements that do not fit within the definitions of Signals Intelligence (SIGINT), Imagery Intelligence (IMINT), or Human Intelligence (HUMINT).
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Vela 4A was an American reconnaissance satellite to detect explosions and nuclear tests on land and in space. It was released together with Vela 4B, ERS 18, OV5 1 and OV5 3.
Vela 4B was an American reconnaissance satellite to detect explosions and nuclear tests on land and in space. It was released together with Vela 4A, ERS 18, OV5 1 and OV5 3.
Vela 5A was an American reconnaissance satellite to detect explosions and nuclear tests on land and in space. It was released together with Vela 5B, OV5 5, OV5 6 and OV5 9.
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