On September 22, 1979, the United States surveillance satellite Vela Hotel 6911 observed a double flash at 00:23 GMT. The flash was detected at approximately 47 degrees South, 40 degrees East. This area is between The Prince George Islands of South Africa and Bouvet Island, which is owned by Norway, but is very small and totally uninhabited.
In the weeks and months that followed, elevated levels of iodine 131, which is a short half life product nuclear fission, were discovered in the thyroid glands of sheep in Tasmania and Victoria , directly where the prevailing wind patterns would distribute the fallout. However, US Air Force planes searched the area in the days following the flash and were unable to find any traces of radiation. It is noted that the low pressure area that surrounded the suspected test area was not searched by the Air Force.
Some have said that the Vela Incident was the result of a meteorite impact. These impacts, such as the Tungusta Event in Siberia in 1908, do generate explosions that are similar in some ways to a nuclear detonation. They can range from the low kilotons to the multiple megaton level, such as the Tungusta Event. However, they do not produce the distinctive "double flash" of a nuclear weapon.
Others have stated that the satellite was past its functional service life and was fooled by the impact of a micrometeorite and the resulting dust reflected light at the satellite. However, the scientists that worked on the Vela Hotel program and Los Alamos Labs have stated that they believe that the satellite was functioning correctly and reported the flash as it had been designed to do.
If we are to accept that as true, the next question was who did it? The top suspects are South Africa, Israel, India, and France. All had nuclear weapons programs at the time.
India is usually discounted, because although they are a nuclear nation, and performed a test in 1974, the test location was very far from their territory and the Indian Navy did not have a large presence there at the time. France comes into play because the site was not too far from the French Kergulen Islands and the French had a history of atmospheric tests in the South Pacific.Therefore, some have postulated that the event was a test of a French Neutron Bomb. Israel is the hardest of the four to say yes or no about, because the position of the Israeli Government has always been to neither confirm nor deny their nuclear program and capabilities. The most likely culprit is the Republic of South Africa. The incident took place very close to their territory and they were known to have nuclear program at the time. However, some have said that the South Africans could not have produced a weapon by that time and that all possible nuclear weapons from South Africa have been accounted for.
Several books have been written about the event, and most allege that it was a joint Israeli-South African test, designed to be small enough to escape detection. In 1994, Dieter Gerhardt ,a former South African Naval officer and convicted Soviet spy after his release from prison in South Africa, said:
"Although I was not directly involved in planning or carrying out the operation, I learned unofficially that the flash was produced by an Israeli-South African test, code-named Operation Phoenix. The explosion was clean and was not supposed to be detected. But they were not as smart as they thought, and the weather changed – so the Americans were able to pick it up."
Now for full disclosure: This is all rumor and conjecture and there are a lot of people who state that not only was there no nuclear explosion, there was no event at all, and it was all a result of faulty equipment. But that is no fun.