how do i get there?

i just completed kikowani station.. and the only mission avalible right now is the alpha site mission, and the door in order to get to the mission is blocked.. so how do i get the door unlocked?    

Are you sure your going the right way, I came across afew sections that prevented me from going the most direct way to the beacon, forcing me to back track and take a much longer route, check the map and see if there is another path, as the map tends to be a much better indicator on how to get from point A to B than the compass waypoint.

The best I can recall is taking an underground passage to the beacon, I think it may have been a road tunnel system

Did you make the same thread on the B.Net forums? I recall someone asking the exact same thing there... 
 
There are 2 distinct entrances and exits to the ONI Alpha Site area. One set is always locked. The other is open. Make a nice round around the locked one and go. If not, go back to the Kizingo Boulevard Flashback point and move from there. Should be faily linear from there onwards.