Didn't the Doctor say that the silence are parasites that live of our creations? Which is why they needed us to invent the spacesuit in the first place before they could manipulate it into something they needed?
Then how could they have built that fake Tardis? They would have had to wait for us to create it first wouldn't they? Or am I completely of the mark on this one?
Also the astronaut was seen coming out of a lake in the first episode so could the silence have simply needed a suit that would allow someone to walk in and out of water, (would a spacesuit allow this?) and hence kill the doctor? As there was a silence there watching the doctor die, they might have planned the whole thing.