3D Master
Rear Admiral
The real question is, after failing to kill Sarah Connor in the first film, why didn't they send the T-1000 back in time a day before the T-800 arrived, and suprise her all over again? Better yet, go back and kill her parents.
In the unfilmed opening scene of T2, we find that the T-800 and the T-1000 were sent back at the same time. Skynet is defeated; and its last ditch effort it sends two Terminators back through time.