Unexplained: the 1979 Indian Ocean Flash

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In August of 1963, against the backdrop of heightened Cold War tensions and the harrowing spectre of the Cuban Missile Crisis just a year prior, the governments of the United States, United Kingdom, and the Soviet Union signed the Partial Nuclear Test Ban Treaty. The treaty emerged as a response to years of escalating nuclear tensions, aiming to curtail the alarming proliferation and development of thermonuclear warheads. Central to this accord was the prohibition of nuclear tests in the earth’s atmosphere, outer space, and beneath the ocean depths, marking a critical juncture in the collective endeavour to mitigate the threat of nuclear cataclysm.

In the wake of the treaty, the United States embarked on a strategic initiative known as Project Vela, aimed at advancing technology capable of monitoring and detecting nuclear detonations. Central to this initiative was the deployment of twelve Vela satellites, orbiting the Earth to ensure compliance with the treaty. The Vela satellites were equipped with bhangmeters, specialised sensors measuring the intensity of electromagnetic radiation. The initial explosion of a nuclear warhead creates a fiercely bright fireball, out of which forms a rapidly expanding shockwave. This shockwave monetarily conceals the fireball before dissipating into the surrounding atmosphere, creating a characteristic ‘double flash’ of light. Between 1963 and 1979, the satellites precisely detected 41 nuclear tests, mostly from non-signatory countries, establishing their reliability and accuracy for the US government.

On 22 September 1979, at 03:53 AM local time, satellite Vela 5B detected the characteristic ‘double flash’ of light off the coast of the uninhabited Prince Edward Islands in the Indian Ocean, a remote territory of South Africa. According to Vela 5B’s bhangmeters, the cause of the flash was none other than a low-yield nuclear blast.

Light readings taken by the two bhangmeters on Vela 5B, displaying the distinctive ‘double flash’ pattern.

The event, later dubbed the ‘Vela Incident,’ sparked real concern within the circles of U.S. national security. The American intelligence community was united in its belief that the flash was a nuclear test, with the CIA reporting to President Jimmy Carter that the likelihood was “90% plus”. Additionally, the U.S. Naval Research Laboratory provided hydroacoustic data collected by its expansive global underwater sensor network that seemed to corroborate this hypothesis. The giant radio telescope at the Arecibo Observatory, Puerto Rico, also recorded a major ionospheric disturbance on 22 September, closely resembling signatures previously associated with recorded nuclear blasts. Finally, a subsequent investigation conducted in October 1979 found that sheep in Australia exhibited elevated levels of Iodine-131 in their thyroid glands, a by-product of nuclear explosions.

The implications bore grave significance; if the ‘double flash’ indeed proved to be a nuclear detonation, it would carry profound ramifications for both the United States and the global community. Did this event constitute a violation of the test ban treaty, or did it herald the emergence of an unknown party onto the nuclear stage?

Amidst the backdrop of the Cold War, suspicion swiftly turned to the Soviet Union. The US Defence Intelligence Agency reported that the USSR may have secretly detonated a device in the Indian Ocean in an attempt to undermine the integrity of the test ban treaty. Yet, several factors cast doubt on this hypothesis. Firstly, the Soviets had relatively little to gain from covert testing, given their well-established nuclear capabilities, while the discovery of such activity would have undoubtedly escalated global nuclear tensions. Secondly, and perhaps more critically, the location of the flash in the southern Indian Ocean appeared incongruous with Soviet testing patterns since the Soviets had predominantly conducted their nuclear tests in Kazakhstan and on the island of Novaya Zemlya.

Indeed the location of the blast pointed to a different, perhaps more worrying culprit – the Apartheid regime of South Africa. Since the mid-1960s, as international condemnation mounted over the imprisonment of Nelson Mandela, the National Party of South Africa had been growing increasingly concerned for its survival, fuelling new research into weapons of mass destruction. In 1965, with American aid, South Africa set up its first nuclear reactor, SAFARI-1, at the Pelindaba research centre west of Pretoria, and began to develop its domestic uranium mining and enrichment capability.

In 1977, the government formalised its commitment to strategic deterrence capability as the primary objective of its nuclear programme, which up to that point had been officially for peaceful purposes. This transformation shifted the responsibility for nuclear development from South Africa’s Atomic Energy Board to the state-owned weapons company, Armscor; the hope being that nuclear weapons would deter Warsaw Pact involvement in the Border War (1966-1990) being fought against Communist insurgents in Namibia. But while this change was meant to be secret, South African preparations for a test site in the Kalahari Desert were spotted by a Soviet Satellite in August 1977. This revelation alerted the international community to the Apartheid regime’s nuclear ambitions. Thus, despite the National Party government officially denying its nuclear weapons programme, it seemed entirely possible that the double-flash could have indeed marked South Africa’s inaugural nuclear test.

There was one problem with this theory; US intelligence suggested that, although South Africa’s nuclear weapons programme was progressing rapidly, it was still months, if not years away from constructing its first nuclear bomb. This suggested that, if the double-flash was caused by a nuclear test, South Africa likely had help from another country. Very quickly, US intelligence identified the probable identity of this collaborator – the State of Israel.

The global intelligence community widely agrees that Israel has had a nuclear weapons capability since the mid-1960s, developed in secret at the Dimona research centre in the Negev Desert. Initially, as Israel gained independence in 1948, the young nation officially condemned the Apartheid regime, hoping to curry favour with majority-black African nations. But after the 1973 Yom Kippur War, Arab threats of an oil embargo were largely able to strong-arm African countries to break off relations with Israel. As a result, the 1970s saw Israel and South Africa deepen their economic and military ties, with Israel becoming a major arms supplier of the South African Defence Force in the Border War. This relationship even extended to Israel providing South Africa with its ‘Jericho’ ballistic missile system.

Thus, it was hardly a stretch of the imagination to allege that the Israelis and South Africans were engaged in a collaborative nuclear program. Indeed, it was also known that Israeli scientists were working at the Pelindaba nuclear plant in South Africa. Given Israel’s relatively small size, it was plausible that they had not had the opportunity to test their nuclear capabilities; by performing a test in the Indian Ocean, Israel could ensure secrecy, whilst maintaining plausible deniability. In exchange, South Africa would gain valuable nuclear knowledge by providing support to the Israeli effort. This theory, that the Vela Incident was a joint South African-Israeli nuclear test, is the most widely accepted explanation amongst independent researchers today – and it seems to have been the tacit conclusion of the US leadership. Published in 2010, President Jimmy Carter’s White House Diaries records on 27 February 1980 that “We have a growing belief among our scientists that the Israelis did indeed conduct a nuclear test explosion in the ocean near the southern end of South Africa.”

However, while the Carter administration may have privately accepted the likelihood of a South African-Israeli nuclear test, acknowledging this publicly would have been political suicide. This was because Jimmy Carter had invested a significant portion of his presidency in mediating the Arab-Israeli peace process, culminating in the Camp David Accords of September 1978, which normalized relations between Israel and Egypt. As Carter vied for re-election against Republican challenger Ronald Reagan in 1980, his administration hoped to tout the Arab-Israeli peace process to the American electorate. To announce that Israel had tested a nuclear weapon would cast serious doubt on the idea that the Middle East was heading towards peace. Moreover, in 1977 the State Department had levied a series of harsh sanctions against Pakistan due to its runaway nuclear programme; if Carter was forced to apply similar sanctions on Israel, as looked likely, America’s entire foreign policy position in the Middle East would be upended.

For this reason, the Carter administration seized upon the idea that the double-flash could have a natural explanation. The White House appointed MIT professor Jack Ruina to chair an investigation into the incident but withheld any intelligence information which related to Israel or South Africa. The Ruina probe focused on the discrepancy between the readings of Vela 5B’s two bhangmeters, ultimately concluding that a nuclear blast was not to blame. Instead, in its final report of May 1980, the investigation suggested that the first flash could have been caused by a micrometeoroid striking the satellite, and the second flash by sunlight reflecting off the meteoroid’s debris. Whilst this became the semi-official position of the US government, the report was met with shock and outrage from the American intelligence community, who believed the Ruina probe was politically motivated.

Ultimately, the Vela Incident remains a mystery of the atomic age. While a joint South African-Israeli nuclear test is the most plausible explanation, a meteor strike is still a distinct possibility, yet without a clear ‘smoking gun’ it is hard to pin the blame on any one factor. Today, the Indian Ocean flash of 1979 is an enduring testament, firstly, to the lengths the US government will take to deceive its own people, should it be politically convenient. Secondly, the Vela Incident is an interesting window into the secretive nuclear programme of the State of Israel. After the fall of the Apartheid regime, South Africa became the first, and to date, the only country to give up its nuclear weapons. But Israel currently maintains a policy of neither confirming nor denying its strategic deterrence capability. The Vela Incident is a major piece of evidence to support the idea that Israel does possess nuclear weapons, and this fact continues to carry significant, although rarely discussed, implications for the geopolitics of the Middle East today.



Weiss, L., 2014. Moving Beyond Pretense: Nuclear Power and Nonproliferation. Strategic Studies Institute, US Army War College

Van Wyk, J., 2021. Nuclear Energy in South Africa. South African Institute of International Affairs.