Just curious...

If say one of the evil countries in the world decided to launch an attack, would it be possible to set the GPS satellites to send incorrect information and perhaps even lead the target missile back to where it started ??

That would be a cool thing.

Although, I imagine, we are relying on GPS more and more in the western world so that would probably lead to some catastrophic disasters, too...

I wondered what the thoughts are on this.

Cheers

The GPS signal can be scrambled so only military users can access it, and it's accuracy can be altered so again, only military users get full granularity. It can't be used to turn missiles around though, as it relies on the time difference between the signals sent from different satellites, and to try and fake the signals to target one missile would completely render the whole system inoperable for everyone else during this period. Anyway, most missiles have other guidance systems, a magnetometer (compass) and inertial systems (so they can 'feel' if they move), so the effect is not certain.

Screwing with GPS would only affect cruise missiles that fly anyway, non MIRVing ICBMs have a ballistic trajectory after their boost phase. MIRVs can steer, but they don't use GPS.

Anyway, Russia has GLONASS, China is launching a GPS system, and so is Europe (Galileo), so as time goes on, there will be multiple sources of GPS data. Getting them all to scramble at the same time ain't going to happen.

Yes but electromagnetic pulse is very close to the same time.