Given the universe's tasteless sense of comedic timing, I wouldn't be too surprised if a Tunguska-scale meteor lands right on DC, Moscow or Beijing at exactly

Given the universe's tasteless sense of comedic timing, I wouldn't be too surprised if a Tunguska-scale meteor lands right on DC, Moscow or Beijing at exactly the wrong time during an international crisis. Still, in principle, the Russians and Americans, and I believe the Chinese, have satellites that detect the distinctive radiation burst from a nuclear explosion. (There's a detector on each GPS satellite.) So it /should/ fail to pass some of the automatic and manual thresholds before we're off to press the button. But in a tense situation, ambiguous data... one does worry a bit. There's been ambiguity with the detectors before. (Was there, or wasn't there, a nuclear explosion in the south Indian ocean in 1979? https://en.m.wikipedia.org/wiki/Vela_incident https://en.m.wikipedia.org/wiki/Vela_incident )