In 1979, a mysterious flash occurred over the southern ocean that could have been a nuclear bomb.

by Brian Dunning

Filed under History & Pseudohistory, Urban Legends

Skeptoid Podcast #592

October 10, 2017

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Something happened on the ocean on September 22, 1979 between South Africa and Antarctica. Some say it was a nuclear explosion; some say it was a natural event of some kind. Nobody's known to have seen it; all we have are some remote detections, but they don't add up very well. We also have some international politics, some government panels and coverups, some declassified documents covered in redactions, and a whole lot of data. We also have satellites and spies. This was the famous Vela Incident of 1979, also called the South Atlantic Flash. Today we're going to dive into the records as history slowly unfolded over about forty years, and see if we can figured out what happened.

Today's podcast is noteworthy in that I believe it holds the record for an idea sitting in my folder longer than any other without being produced: over nine years. It was back in 2008 that this topic was first emailed to me as an episode suggestion. I did a bit of preliminary research at the time, and concluded that the question of the Vela Incident simply didn't have any answer, which on the one hand is an answer in itself, of a sort; but on the other hand, it doesn't make for the most exciting Skeptoid episode. However, new information emerged, and now we have a bit clearer picture.

At the time, in 2008, the latest and greatest information on the Vela Incident was in a 2006 article from the National Security Archive at George Washington University. So let's begin with what was known for the first 30 years following the incident.

It all started with the Vela satellites, a fleet of twelve satellites launched from 1963 to 1970, intended to monitor compliance with the Partial Test Ban Treaty between the United States, United Kingdom, and the Soviet Union. This treaty allowed only underground nuclear testing, so the Vela satellites were built to detect any explosions either in space or in the atmosphere. Then, on September 22, 1979, about 3:00am local time, ba-boom. Vela 6911 caught the distinctive double flash of a nuclear detonation. The event was logged as Vela Alert 747.

Let's take a moment to talk about what happens during the first few milliseconds when a nuclear explosion happens. When the explosion begins, the device itself quickly goes to a temperature of about ten million kelvins. The X-rays and ultraviolet waves emitted heat the air within a few meters of the device to a temperature of about one million kelvins, which makes it extremely incandescent and causes an incredibly bright flash. Meanwhile, inside that cloud of bright gas, a shockwave expands, pushed by the explosion itself. Inside that shockwave, everything is a plasma, where the atomic particles are actually dissociated. Plasmas are opaque, because they absorb electromagnetic radiation at all frequencies. As that shockwave expands, it overtakes those first few meters of incandescent air, and once it does, its opacity actually shades it like a curtain. From there, the shockwave expands outward spherically; and as the plasma thins and diminishes it becomes increasingly transparent, allowing the expanding fireball to shine forth with its full brilliance. Thus, when a nuclear explosion happens, we actually get a double flash. The larger the yield, the longer the space between the flashes; ranging from 30 milliseconds for the smallest devices to half a second for larger ones.

What Alert 747 detected is this characteristic double flash, with a gap between the flashes indicating a small yield of between two and three kilotons. It was picked up on the satellite's bhangmeter. All twelve Velas were equipped with X-ray detectors, but the later six, known as the Advanced Vela satellites, also added bhangmeters.

You are asking what a bhangmeter is, so I will tell you. It's named after bhang, an edible form of cannibis popular in Hindu festivals, and evidently well known to the scientists who were working on this new type of radiometric sensor for detecting nuclear tests. One day at Los Alamos, one scientist observed that you'd have to be "on something" to think that this type of detector could determine a device's yield. But determine yield it could, so they duly dubbed it the bhangmeter. That story is, by all accounts, absolutely true.

President Jimmy Carter was in office, and word spread quickly that this detection of a nuclear blast had been made. Carter wrote in his diary for that very same day (published in 2010):

There was indication of a nuclear explosion in the region of South Africa — either South Africa, Israel using a ship at sea, or nothing.

So there's a lot to unpack here, just in these first hours. Obviously the probability that a nuclear weapon had been detonated in the atmosphere was a treaty violation, and that's big. Second, note that right away, as early as that very same day, the administration already suspected Israel and/or South Africa were responsible.

The importance of definitively answering this question was clear. Carter ordered his science advisor, Dr. Frank Press, to assemble a panel of outside experts to look at all the evidence. The panel was chaired by Dr. Jack Ruina, a former head of DARPA. The Ruina Panel issued its report in May of 1980. In short, it found the deviances between the light flash recorded by Vela and light flashes from known nuclear detonations too significant, and it found the lack of corroborating data which must exist to be problematic. The Ruina Panel's conclusion was that the most likely explanation for the Vela Incident was a meteoroid strike on the satellite itself, where the meteor's initial entry into the field of view was responsible for the initial flash, and the spread of debris from the impact responsible for the second flash.

A lot of briefs were written by lot of experts from the Air Force, from our National Laboratories, NGOs, and government over the next two or three years, and were quickly classified. They've since been declassified, and we can now read them. Nearly all were equivocal. About the only thing they agreed on was that there was no proof that a nuclear detonation had taken place. Most concluded that it was still the most likely explanation. Some also considered a variety of natural events, like a lightning superbolt making a double flash. One from the Defense Intelligence Agency found that the chances of the Ruina Panel's meteoroid causing the signal would be a once in a hundred billion years incident.

Right after the alert, the Air Force dispatched WC-135B Constant Phoenix aircraft to sample the atmosphere in the region of the flash. 25 sorties were flown from a classified air base totaling 230.4 hours. What was found? Bupkis. No fresh fission products. It looked like the flash was going to always remain a mystery.

However, in 2016, additional information was declassified. It came from the files of Gerard Smith, Jimmy Carter's ambassador to the International Atomic Energy Agency. There was a lot in there that, put together, painted a pretty clear picture. After Alert 747, the State Department put out a series of memos on diplomatic strategy with South Africa if the news leaked, which it did; virtually confirming that the flash was indeed a diplomatic matter. In addition, hydroacoustic data from that exact spot in the ocean, from that exact time, had been analyzed by the US Naval Research Laboratory and found to be "unique to nuclear shots in a maritime environment." At least two spies, retired CIA officer Tyler Drumheller and retired KGB officer Dieter Gerhardt, said they knew it to have been a nuclear test called Operation Phoenix. Finally there was a variety of information from a number of sources that indicated the Ruina report had been a "whitewash", using flimsy evidence to arrive at a preferred conclusion of a natural event for political reasons, while the panel's actual research pointed toward a nuclear event, including the fact that experts would not have expected the aerial sampling to find anything. The National Security Archives provides links to dozens of these documents.

Why Israel and South Africa? And how did Carter know this within hours? The two nations' relationship was an interesting one. Israel wanted nuclear weapons but the international community didn't want them to. South Africa, with its official policy of apartheid, was an international pariah; but they did have one thing that everyone wanted: uranium. What better partnership could there be? Two nations, both outcast internationally, with a common goal and the expertise and the resources. We know that South Africa did provide Israel with uranium in the 1960s and again in the 1970s. South Africa had been caught preparing a site for underground nuclear tests in 1977 by both the Soviet Union and the United States, but was compelled to shut it down to protect its contract for French nuclear reactors. Israel's nuclear weapons capability has always been an open secret, but they've never been proven to have conducted a successful test.

Let's throw one more piece of circumstantial evidence onto the pile. In 1982, the Air Force produced a history of the operations of the Air Force Technical Applications Center (AFTAC) from 1979 - 1980, which detailed the air sampling done by the WC-135B aircraft. In this report, it was added:

Alert 747, the unexplained event that occurred on 22 September 1979 in the Southern Hemisphere, brought to light AFTAC's meager resources in that area of the world. This generated high-level interest in the AEDS [Atomic Energy Detection System] program and a reevaluation of the system to improve coverage in the Southern Hemisphere.

This was then done, by adding additional resources which were collectively called the Auxiliary Seismic Network. The Air Force knew that the resources it had in place in 1979 simply weren't adequate to definitively detect a nuclear test. And if the Air Force knew it, then it's probably a safe bet that Israeli intelligence knew it too. The uncertainty surrounding the detection and potentially corroborating evidence was not necessarily due to that evidence being nonexistent, but rather to our inadequate ability to collect it.

Case proven and closed? No, but settled (I think) to a sufficient degree of satisfaction. The Vela Incident — or the South Atlantic Flash — or Alert 747 — or Operation Phoenix — was a joint Israeli-South African nuclear test of less than 3 kilotons on the ocean surface. So there we have it: a tale of intrigue, espionage, and satellites from the cold war, probably — if not definitively — solved.

Addendum: Further evidence was published in 2018 about the discovery of radionuclides in Australian sheep that could only have come from such an atomic explosion. Details are in Skeptoid #660. –BD



By Brian Dunning

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