Well, the Empire doesn't consider a small, one man fighter to be any threat or they'd have a tighter defense. An analysis of the plans, provided by Princess LEEAAH, has demonstrated a weakness in the battle station.
The approach will not be easy. You're required to maneuver straight down this trench and skim the surface to this point. The target area is only two meters wide. Its a small thermal exhaust port right below the main port.
The shaft leads directly to the reactor system. A precise hit will start a chain reaction which should destroy the station. Only a precise hit will set up a chain reaction. The shaft is ray-shielded so you'll have to use proton torpedoes.