On 22 September 1979 the Americans detected an apparent nuclear detonation somewhere in the South Atlantic.
Thus began an amazing story involving the Soviets, Israel, USA, and South Africa.
On 22 September 1979 around 00:53 GMT, the Vela 6911 satellite detected the characteristic double flash of an atmospheric nuclear explosion
apparently over the Indian Ocean or South Atlantic. The test location was later localized at 47 deg. S, 40 deg. E in the Indian Ocean, in the vicinity
of South Africa's Prince Edward Island, by hydroacoustic data. Due to the position ambiguity of the initial detection (the Vela optical sensors were
not imaging sensors and could did not detect location), the location is variously described as being in the Indian Ocean or South Atlantic. The
characteristics of the light curve indicated that it was a low kiloton explosion (approximately 3 kt). The hydroacoustic signal indicated a low
altitude explosion. A major and lingering controversy erupted over the interpretation of this apparent detection.
The Vela Incident
There are theories that this was never a detonation, that it was a
micrometeorite might have struck the satellite and dislodged a piece of it
skin. Reflecting sunlight into the optical system of one sensor but not into that of its neighbor, the debris might have caused the questionable
event
The Vela satellites had never been wrong before:
In conducting their readout the AFTAC technicians saw a double humped signal that corresponded to the double flash associated with a nuclear
explosion. In the 41 previous occurrences when a Vela satellite detected such a double flash (including the 12 Vela 6911 detections), subsequent data
confirmed that a nuclear detonation had actually occurred. The signal Vela 6911 had apparently detected came from a remote region of the world, for
the territory in view of its bhangmeters encompassed 3,000 miles in diameter - the southern tip of Africa, the Indian Ocean, the South Atlantic, and a
bit of Antarctica.
Link
The Ruina panel that was tasked with investigating the incident ultimately released the following:
the signal "was probably not from a nuclear explosion. Although we cannot rule out that this signal was of nuclear origin".
There have been reports that the Israeli's worked with South Africa to help perfect a neutron bomb (which explained the relative lack of nuclear
fallout).
Dieter Gerhard, a communist spy and Commander of Simonstown naval base confirmed it was a joint Israeli/South African test code-named Operation
Phoenix (also thought to be part of Israel's Samson Option).
South African Deputy Foreign Minister Aziz Pahad was quoted as confirming that the 22 September 1979 flash over the Indian Ocean was indeed from a
South African nuclear test. The article said that Israel helped South Africa develop its bomb designs in return for 550 tons of raw uranium and other
assistance.
And yet, nothing has ever been confirmed by Israel or the Americans.
What we do know is that the Americans knew (and supported) about Israel's nuclear aspirations from the 1970's - the conclusion we can draw is that
the USA may inadvertently have helped make the Apartheid government a nuclear power.
The other thread in ATS does not discuss the more controversial aspect to this incident and I thought it required another look:
The Vela Incident 
