‘On 22 September 1979, sometime around 3:00am local time, a US Atomic Energy Detection System satellite recorded a pattern of intense flashes in a remote portion of the Indian Ocean. Moments later an unusual, fast-moving ionospheric disturbance was detected by the Arecibo Observatory in Puerto Rico, and at about the same time a distant, muffled thud was overheard by the US Navy’s undersea Sound Surveillance System (SOSUS). Evidently something violent and explosive had transpired in the ocean off the southern tip of Africa.
Examination of the data gathered by satellite Vela 6911 strongly suggested that the cause of these disturbances was a nuclear device. The pattern of flashes exactly matched that of prior nuclear detections, and no other phenomenon was known to produce the same millisecond-scale signature. Unfortunately, US intelligence agencies were uncertain who was responsible for the detonation, and the US government was conspicuously reluctant to acknowledge it at all.’