The Vela Incident: Did an American satellite detect a secret nuclear test in 1979?

It began with an unusual flash detected off the coast of South Africa by an aging American satellite — and to this day, debate continues over whether this odd Cold War event involved an illicit atmospheric nuclear test.

The strange story of the "South Atlantic Flash," better known as the Vela Incident, began on Sept. 22, 1979. At that time, Vela 6911, a satellite in a constellation developed by the United States for the specific purpose of detecting nuclear detonations, observed something that immediately alarmed officials: a peculiar flash of light emanating from somewhere over the South Atlantic Ocean.

A significant part of what concerned U.S. officials at the time had been the double flash of light detected during the event — a distinctive feature that strongly resembled the flashes produced by a nuclear explosion in Earth's atmosphere. The characteristic double flash results from the rapidly changing brightness of the fireb...