Vela Incident - Wikipedia

On September 22, 1979, strong evidence pointed to Israel performing a nuclear test in the Indian Ocean. From the article:

"The Vela Incident, also known as the South Atlantic Flash, was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the Prince Edward Islands off Antarctica. The more common theory among those who believe the flash was of nuclear origin is that it resulted from a joint South African–Israeli nuclear test.[1] In 2016, researchers from George Washington University's National Security Archive noted that the debate over the South Atlantic Flash has shifted over the last few years to the side of a man-made weapon test.[2][3] In 2018, a new study claimed that it is highly likely that it was a nuclear test, conducted by Israel.[4][5]

While a double-flash signal is characteristic of a nuclear weapons test in the atmosphere, the signal could also have been due to a meteoroid hitting the Vela satellite. All of the previous 41 double flashes detected by the Vela satellites were confirmed to be nuclear explosions.[6][7][8] Some information about the event remains classified."

Here is a longer article for those interested.

https://www.mepc.org/israels-1979-nuclear-test-and-us-cover