A decent size particle accelerator placed on the moon could hit targets in earth orbit with about a 1.2 second delay between firing and impact; fairly negligible when your target is incapable of dodging (or detecting the incoming fire, for that matter). With a minimum of interference from the "vacuum" of space, a stream of charged particles at near lightspeed would at minimum wreak holy electronic havoc on any satellite, and at maximum partially vaporize it and/or shove it spinning uncontrollably into a decaying orbit.
Neither cheap nor easy to implement, but horrifically effective against any target in Earth orbit. Heck, you might even be able to justify it under the pretense that it would be fairly useless in attacking anything on the surface of the Earth.