@phasorburn @stuartyeates A colleague told me about a talk she saw at a UN conference on nuclear war (!!) where they did a bunch of simulations and (this is my second-hand understanding) that a lot of the radiation from a nuclear explosion in orbit ends up getting trapped in Earth's magnetic field lines, so many (possibly all) satellites fly through and get fried, no matter where the explosion was.

Nuclear explosions in orbit (or anywhere!) are very very bad.