Also bear in mind that satellites must be radiation hardened to function at all, because they're already in a high-radiation environment.

I have no doubt a military could build a weapon that could use some form of EMP pulse to completely destroy my cell phone if it were an equivalent distance from a ground-based attack site, in an environment where it wouldn't be simply destroyed. Heck, I wouldn't be surprised there's some researchers who could put something together from their test bench and bits lying around in the lab in a day or two. Doing it to a hardened target is going to be much harder.