“There was indication of a nuclear explosion in the region of South Africa—either South Africa, Israel using a ship at sea, or nothing.”
President Jimmy Carter — White House Diary (September 22 1979) 
“Shortly before sunrise on Sept. 22, 1979, a U.S. surveillance satellite known as Vela 6911 recorded an unusual double flash as it orbited the earth above the South Atlantic. At Patrick Air Force Base in Florida, where it was still nighttime on Sept. 21, the staff in charge of monitoring the satellite’s transmissions saw the unmistakable pattern produced by a nuclear explosion, something U.S. satellites had detected on dozens of previous occasions in the wake of nuclear tests. The Air Force base issued an alert overnight, and President Jimmy Carter quickly called a meeting in the White House Situation Room the next day.”
Blast From the Past — Foreign Policy
“We had operational successes, most importantly regarding Pretoria’s nuclear capability. My sources collectively provided incontrovertible evidence that the apartheid government had in fact tested a nuclear bomb in the South Atlantic in 1979, and that they had developed a delivery system with assistance from the Israelis.”
CIA clandestine service officer Tyler Drumheller
“A panel of scientists carefully selected by the Carter White House produced a report in 1980 that did not rule out a test, but said the probability of its being something other than a test was more likely. That conclusion is now derided by nearly all independent observers who have studied and reported on the issue.”
Leonard Weiss — Bulletin of the Atomic Scientists (August 3 2018)
“Now, 40 years later, there is a scientific and historical consensus that it was a nuclear test and that it had to be Israeli.”
Avner Cohen (September 22 2019)
September 22 2020 — A CIA-sponsored panel of well-respected scientists concluded that a mysterious flash detected by a U.S. Vela satellite over the South Atlantic on the night of September 22 1979 was likely a nuclear test. Four decades later, this mysterious double flash still matters, and the debate is not over. What do you think? Follow us on Twitter: @INTEL_TODAY
On September 22 1979, at 00:53 GMT, the American Vela satellite 6911 reported the characteristic double flash of a small atmospheric nuclear explosion of two to three kilotons, in the Indian Ocean between the Crozet Islands and the Prince Edward Islands.
“The previous 41 double flashes the Vela satellites detected were all subsequently confirmed to be nuclear explosions. There was, and remains, much doubt as to whether the satellite’s observations were accurate.” [WIKIPEDIA]
In December 2018, the National Security Archive posted a large number of recently declassified files regarding the ‘Vela Incident’.
Within days, a larger White House scientific panel would assert that the nuclear test thesis was unlikely, but in 1980 additional evidence emerged that led a senior U.S. intelligence official to disparage the White House study as a “whitewash” influenced by “political considerations.”
The debate over the “September 22 Event” or the “South Atlantic flash” continues to this day, including whether Israel may have staged a test with South African assistance.
The newest information, included in today’s posting, comes from recently declassified documents in the files of Ambassador Gerard C. Smith at the National Archives.
The study confirms that it is highly likely that the “Vela incident” was a indeed nuclear test, almost certainly conducted by Israel.
In August 2018, Leonard Weiss — a visiting scholar at Stanford University’s Center for International Security and Cooperation and a member of the National Advisory Board of the Center for Arms Control — published an important piece: A double-flash from the past and Israel’s nuclear arsenal in the Bulletin of the Atomic Scientists.
Important new and dispositive evidence that the “flash” was a nuclear test has been added recently by two respected scientists, Christopher Wright of the Australian Defense Force Academy and Lars-Eric De Geer of the Swedish Defense Research Agency (Ret.), writing in the journal Science & Global Security.
Using data first gathered by Distinguished Professor Lester VanMiddlesworth of the University of Tennessee on radioactivity found in the thyroids of sheep in Australia within the time period following the “flash,” plus meteorological data from the time and some radionuclide and hydro-acoustic data released by the US government, Wright and De Geer have produced an analysis of the Vela event that removes virtually all doubt that the “flash” was a nuclear explosion.
The explosion was one of small yield, perhaps to simulate the result of firing a nuclear artillery shell. Wright and De Geer do not speculate on who might have performed the test. But none of the five recognized nuclear weapon states would feel the need to perform a small clandestine test of that kind.
Similarly, in 1979, neither India nor Pakistan nor South Africa had nuclear development and logistics capabilities at a stage where a nuclear test of that kind in that area was feasible for them. Israel was the only country that had the technical ability and policy motivation to carry out such a clandestine test, which, according to some sources, was the last of several and was detected by the Vela satellite because of a sudden change in cloud cover.
The new study by Wright and De Geer should receive wide attention because it provides a test of the commitment by the international community to nuclear arms control and nonproliferation norms.
While a comprehensive nuclear test ban is yet to be achieved, the nations of the world did manage to put in place an extremely important arms control, non-proliferation, and environmental protection measure called The Limited Test Ban Treaty (LTBT). This treaty, which went into force in 1963, bans nuclear explosions in the atmosphere, in outer space, and under water, thus rendering legal only those nuclear tests performed underground.
Israel signed the treaty in 1963 and ratified it in 1964. The Israeli nuclear test puts Israel in violation of the LTBT, which has been signed by 108 countries, including all the officially recognized nuclear weapon states plus India, Pakistan, and Iran.
Israel would also be in violation of the Glenn Amendment to the Arms Export Control Act, a US law passed in 1977, requiring the cutoff of military assistance to any country setting off a nuclear explosion. The president can waive the sanction, but he has to face the issue.
In the meantime, what should be a consequence of the flagrant violation of the Limited Test Ban Treaty?
At a time when public demands for nuclear transparency are loudly and justifiably trumpeted toward Iran and North Korea, which are pariahs in many Western eyes, it is illogical at best and hypocritical at worst for the world, and particularly the United States, to maintain public silence on Israel’s nuclear program, especially in the face of a violation of an important nuclear norm.
For the sake of future progress on arms control, on steps to reduce nuclear risk, and on honest public as well as private communication among governments and their constituents to achieve such progress, it is time to end an existing double standard that has allowed Israel to escape accountability for developing advanced nuclear weapons by violating a major international treaty.
40th Anniversary — Foreign Policy
On the 40th anniversary of the Vela event, Foreign Policy has assembled a team of scientists, academics, former government officials, and nonproliferation experts to analyze the declassified documents and data in the public domain, explain the political and strategic objectives of the key players at the time, and argue why a mysterious flash 40 years ago still matters today.
Nuclear proliferation was just one of the Carter administration’s headaches in late 1979. The president was dealing with a slew of foreign-policy dilemmas, including the build-up to what would become the Iran hostage crisis.
Carter was also preparing for a reelection campaign in which he had hoped to showcase his foreign-policy successes, from brokering Israeli-Egyptian peace to successful arms control talks with Moscow. The possibility that Israel or South Africa, which had deep clandestine defense ties at the time, had tested a nuclear weapon threatened to tarnish that legacy.
And the fact that South Africa’s own nuclear weapons program, which the Carter administration was seeking to stop, was not yet sufficiently advanced to test such a weapon left just one prime suspect: Israel. Leading figures within the administration were therefore keen to bury the story and put forward alternative explanations.
Those alternative explanations were widely dismissed by many members of the scientific and intelligence community at the time; four decades years later, they look even more questionable.
 Jimmy Carter, White House Diary (New York: Farrar, Straus and Giroux, 2010) p. 357.
The Vela Incident: South Atlantic Mystery Flash in September 1979 Raised Questions about Nuclear Test
The 22 September 1979 Vela Incident: The Detected Double-Flash, Science & Global Security, 25:3, 95-124, DOI: 10.1080/08929882.2017.1394047)
The VELA Incident: Declassified Files Shed Light on the Nuclear Test Controversy
Two Years Ago — The VELA Incident : Declassified Files Shed Light on the Nuclear Test Controversy
40 Years Ago — The VELA Incident (September 22 1979)
On This Day — The VELA Incident (September 22 1979)