The Vela incident was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the South African territory of Prince Edward Islands in the Indian Ocean, roughly midway between Africa and Antarctica. Today, most independent researchers believe that the flash was caused by a nuclear explosion—an undeclared joint nuclear test carried out by South Africa and Israel. The cause of the flash remains officially unknown, and some information about the event remains classified by the U.S. government. While it has been suggested that the signal could have been caused by a meteoroid hitting the satellite, the previous 41 double flashes detected by the Vela satellites were caused by nuclear weapons tests. Detection The "double flash", then dubbed the South Atlantic flash, was detected on 22 September 1979, at 00:53 UTC, by the American Vela satellite OPS 6911 (also known as Vela 10 and Vela 5B), which carried various sensors designed to detect nuclear explosions that contravened the Partial Nuclear Test Ban Treaty. In addition to being able to detect gamma rays, X-rays, and neutrons, the satellite also contained two silicon solid-state bhangmeter sensors that could detect the dual light flashes associated with an atmospheric nuclear explosion: the initial brief, intense flash, followed by a second, longer flash. The satellite reported a double flash, which could be characteristic of an atmospheric nuclear explosion of two to three kilotons, in the Indian Ocean between the Crozet Islands (a sparsely inhabited French possession) and the Prince Edward Islands (which belong to South Africa) at . Acoustic data of the Sound Surveillance System (SOSUS) established by United States to detect Soviet submarines and the Missile Impact Locating System (MILS) designed to detect missile nose cone impact locations of test missiles in the Atlantic and Pacific test ranges were searched in an effort to gain more knowledge on the possibility of a nuclear detonation in the region. These data were found not to have enough substantial evidence of a detonation of a nuclear weapon; however a detailed, affirming study regarding MILS data correlating with time and location of the Vela flash was not considered in that finding. United States Air Force (USAF) surveillance aircraft flew 25 sorties over that area of the Indian Ocean from 22 September to 29 October 1979 to carry out atmospheric sampling. Studies of wind patterns confirmed that fall-out from an explosion in