On top of everything else commented, there's the matter of how delicate you need to be about it. I do hope no one ever tries to down a satellite with a railgun,

On top of everything else commented, there's the matter of how delicate you need to be about it. I do hope no one ever tries to down a satellite with a railgun, as debris might create a runaway effect that brings about a dark night. Use lasers, be responsible.