Global Positioning System in Twilight 2000

[Vespers War]

Originally Posted by castlebravo92

GPS satellites would be completely unaffected by EMP. One, EMP is an atmospheric phenomenon caused by high energy photons (ie, gamma rays) hitting the atmosphere. No atmosphere = no EMP. GPS satellites are 20,000 km away.

That's type one EMP. Type two is a gamma ray pulse that doesn't rely on atmospheric effects (but tends to be very weak), and type three is caused by magnetic field distortions from the nuclear blast. Earth's magnetic field extends to 65,000 kilometers on the day side and 6,300,000 kilometers on the night side, so good luck being outside of that.

While there probably won't be EMP effects at GPS satellite altitude from a nuclear bomb, satellites in LEO are definitely vulnerable, and even modern satellites are still vulnerable to type three EMP - a natural geomagnetic storm wiped out a few dozen Starlink satellites last year from the same sort of magnetic field distortions that a nuclear blast would cause.