|Fig. 1: Typical graph of a "double hump" recorded by a bhangmeter during a nuclear explosion.  (Courtesy of the DOE)|
In the wake of the Partial Nuclear Test Ban Treaty, in 1963 the United States launched a series of satellites called "Vela," capable of detecting nuclear explosions in space and the atmosphere. On September 22nd, 1979, Vela 6911 detected an unexpected "double flash" bearing the distinctive features of an atmospheric nuclear explosion. This so called "Vela Incident," "September 22nd Event," or "South Atlantic flash" occurred at 00:52:44 GMT when the satellite detected a flash with the characteristic "double hump" shape associated with the light pattern observed from a nuclear explosion (Fig. 1).  In nuclear explosions, the light rises to an initial peak luminosity with the shock wave, the second rise in luminosity comes from the fireball. 
All other instances of light flashes with this signature have been confirmed nuclear tests, but there exists to this day controversy as to the nature of the satellite's findings.  The so-called Vela Incident is widely assumed to be the result of a joint Israeli-South African nuclear test, but this theory remains is unconfirmed. Other speculations include the reflection of some other non-nuclear event such as lightning at the same time as a meteor hitting the satellite or a technical malfunction since when the flash occurred the Vela satellites were two years past their intended design lifespan. [3,4] The purported explosion was observed in the Indian Ocean, in between the Crozet Islands and the South African Prince Edward Islands.
While the exact circumstances of this event are ambiguous, it is often assumed that the test was conducted by Israel with the help of South Africa. South Africa was primarily suspected due to the proximity of the test to the country. With Israel, however, the speculation was far more presumptive. Prior to the Vela Incident, American intelligence agencies had made the assessment that Israel likely possessed nuclear weapons. Around ten years prior to the flash, Israel chose not to sign the Nuclear Non-Proliferation Treaty despite American suspicion surrounding Israel's nuclear power plant at Dimona. Moreover, journalist Seymour Hersh believes that the Incident had been proceeded by a visit to the site by two Israel Defense Force ships and that the South African navy was present during the actual test.  Despite these indications that Israel and South Africa were responsible for the Vela Incident, no smoking gun has been found to confirm that they are responsible. By 1979, Israel had a well-established policy of nuclear ambiguity, a protocol which it maintains today. In response to inquiries into their potential nuclear weapons program, the country's politicians habitually assert that "[Israel] will not be the first country to introduce nuclear weapons to the [Middle East]." 
Due to the growing pressure from the international political and intelligence communities, the Carter administration decided to form an ad hoc committee to determine the nature of the flash. MIT professor of electrical engineering Jack Ruina was made the chairman of the committee. The panel was asked to ignore political pressures and to focus on evidential analysis. Its findings were released on May 23rd, 1980, and an unclassified version was released in September of that year. They offered one potential alternative explanation that the double flash could have been caused by "the possible reflection of sunlight from a small meteoroid or a piece of space debris passing near the satellite."  The odds of this occurring at the exact time that the satellite recorded the flash were 1 in 100 billion.  However, the panel maintained that a nuclear test was unlikely. 
Whether Vela 6911 captured a low-yield nuclear test or an improbable event in space is one of the greatest mysteries in nuclear history. Some suspect that America had a vested interest in establishing the Vela Incident as a non-nuclear event, due to America's desire to avoid conflict with both South Africa and Israel. The Ruina Panel would suggest that this event is not nuclear. However, when one scientist named Richard Garwin initially saw the data he believed the flash to be nuclear, but he changed his opinion after he participated in the Ruina Panel, casting a shadow of doubt over the objectivity of the panel. Portions of this event still remain classified: the ambiguity shrouding this event is best characterized by Jimmy Carter's White House Diaries: "There was indication of a nuclear explosion in the region of South Africa, either South Africa, Israel using a ship at sea, or nothing." 
© Josh Lange. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 E. W. Hones, D. N. Baker, and W. C. Feldman, "Evaluation of Some Geophysical Events on 22nd September 1979," Los Alamos Scientific Laboratory, LA-8672, April 1981.
 G. E. Barasch, "Light Flash Produced by an Atmospheric Nuclear Explosion," Los Alamos Scientific Laboratory, LASL-79-84, November 1979.
 L. Weiss, "The 1979 South Atlantic Flash: The Case for an Israeli Nuclear Test," Center for International Security and Cooperation, Stanford University, 30 Jul 11.
 L. Weiss, "Israel's 1979 Nuclear Test and the U.S. Cover-Up," Middle East Policy 18, No. 4, 83 (2011).