Ever since the flash was observed by a U.S. “Vela” satellite orbiting above Earth in September 1979, there’s been speculation that it was produced from a nuclear weapon test by Israel.
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The flash was located in the area of Marion and Prince Edward islands, which are in the South Indian Ocean about halfway between Africa and Antarctica.
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The researchers conclude that iodine-131, which is an unstable radioactive form of the element iodine found in the thyroids of some Australian sheep, “would be consistent with them having grazed in the path of a potential radioactive fallout plume from a [September 22, 1979] low-yield nuclear test in the Southern Indian Ocean.”
Thyroid samples from sheep killed in Melbourne were regularly sent to the U.S. for testing—monthly in 1979 but also in the 1950s and 1980s, researchers say.
According to a report in the New Zealand Herald, the sheep had been grazing in an area hit by rain four days after the flash incident was observed, which would have been in the downwind path from the suspected explosion site.
Researcher also said the detection of a “hydroacoustic signal” from underwater listening devices at the time is another piece of evidence pointing to a nuclear test.
There’s more at the link.
Here’s a rather dramatic, overly florid documentary about the Vela Incident. It’s not altogether accurate; for example, the flash was not detected near Bouvet Island, as it claims, but near the Prince Edward Islands. Nevertheless, it provides more information about the initial investigation into the incident.
Almost forty years after the Vela Incident, I suppose there’s not much risk involved in talking about it. I was in a position to know something about it. According to what I was told, then and subsequently, the explosion was to test an initiator for an Israeli nuclear warhead. Apparently only a very small device was tested, because all it had to do was prove that the initiator worked. That would then guarantee the ignition/detonation of a much more powerful nuclear bomb, which would not have to be tested at full strength – something that was sure to be detected, and therefore was most undesirable.
I understood that Israel approached South Africa for assistance in arranging the test in a remote part of the South Atlantic Ocean. The Prince Edward Islands were (and still are) South African possessions. There is no normal sea traffic in the vicinity except to resupply a weather station on Marion Island, once or twice a year. Their extreme isolation therefore made this an ideal location for a very small-scale nuclear test. It would be conducted at sea, not on land, so as to leave as little evidence as possible. It was hoped that the (usually severe) weather conditions in the area would help to mask an atmospheric detonation, so that its very small shock-wave would not be detected. However, the clouds cleared momentarily during the test, allowing a US Vela satellite to detect the characteristic double light pulse of a nuclear explosion.
At the time, both Israel and South Africa denied that the flash was the result of a nuclear explosion. Other evidence was inconclusive, made more so by the difficulty of gathering it in so remote a location. By the time WC-135 “sniffer” aircraft could be sent downwind of such a remote location to test the air (it took days after the blast to get them there), the atmospheric residue of the blast had largely dissipated. I’m not surprised to hear that a small increase in radiation was later detected in sheep in Australia; the “Roaring Forties” would have carried radioactive particles that far without difficulty.
Quite apart from what I heard and was told at the time, Commodore Dieter Gerhardt, then Commanding Officer of the South African Navy Dockyard at Simonstown, and who was later unmasked as a Soviet spy, later confirmed that he had similar information about the Vela incident. Subsequent investigations tend to confirm that what we knew then was substantially correct, although details differ according to the source(s) they used.
I think the latest news report is substantially accurate. If what I learned at the time is correct, it would imply that Israel possessed at least boosted fission weapons, and possibly full-blown thermonuclear bombs, by the early 1980’s. In the almost four decades since then, I’m certain they’ve gone a long way further. They’ve developed their own cruise missiles for a submarine-based deterrent, the so-called “Popeye Turbo” weapon, which suggests that they now have miniaturized thermonuclear warheads to fit them. I’m sure they also have air-launched missiles capable of carrying similar warheads, as well as gravity bombs, probably fitted with guidance systems similar to the JDAM used by the USAF (and Israel). They also developed, and still field, the Jericho series of ballistic missiles.