From what I’ve read about Project Orion, the physical damage from nukes is mostly in the shockwave. The material shockwave doesn’t propagate very far in space, so satellites won’t be blown up by a space nuke.

The EMP is, if I understand right, created by a shockwave in the extremely diffuse plasma of the ionosphere, affecting electrons and ions differently, creating a massive charge separation, and the collapse of that charge separation is what produces the actual EMP. That said, this article is the first I heard of the E1/E3 distinction, so I don’t know enough to be sure of what an EMP would do to satellite electronics.