"GLOBAL ISSUES, LEADERSHIP CHOICES":

Forty years ago this week, a U.S. satellite picked up the distinctive "double flash" of a nuclear bomb being tested. This article from Foreign Policy looks at the historical context of Israel's unauthorized nuclear test and why the U.S. pretended it didn't happen.

"On Sept. 22, 1979, the U.S. Vela satellite recorded the telltale light signal from a nuclear test using detectors called bhangmeters. The satellite, known as Vela 5B or Vela 6911, was one of a number launched in the wake of the 1963 Partial Test Ban Treaty (PTBT), which banned nuclear tests in the atmosphere, underwater, and in outer space. The detected signal was a 'double flash' characteristic of nuclear test signals recorded on 41 previous occasions by Vela satellites. ... Until 1979, they had not detected any illicit explosions among the 41 recorded nuclear events. The satellite in question, Vela 6911, had in fact been retired. ... When it recorded a double flash in 1979, the signal could have come from anywhere within a diameter of several thousand miles. Suspicion quickly fell on South Africa, which was known to be working on a bomb, and even more so on Israel, which had close military connections with South Africa and had an untested nuclear arsenal. ... An Israeli test would force [U.S. president Jimmy Carter] to deal not only with violation of the PTBT, but also with U.S. nonproliferation legislation. The 1977 Glenn Amendment to the Arms Export Control Act mandated an end to arms assistance, and an automatic application of extensive U.S. sanctions, if the president determined any state (other than the nuclear states authorized by the Nuclear Non-Proliferation Treaty) detonated a nuclear explosive after 1977. ... The Carter administration was so afraid to enforce the PTBT against Israel’s 1979 violation that it did what it could to erase or keep hidden evidence of its detection of a test. Subsequent administrations, Republican and Democratic alike, went along with this, and the U.S. government still pretends it knows nothing about any Israeli nuclear weapons."
foreignpolicy.com/2019/09/22/blast-from-the-past-vela-satellite-israel-nuclear-double-flash-1979-ptbt-south-atlantic-south-africa/