After killing Hugo Lacerda, head back up to where you should have seen the captain. Go out the door.Above you, there is a ledge you can jump and hang on to. Pull yourself up and watch out for two gaurds that will be walking around. Head past the bright light and go around the corner.You will be on a narrow walkway. Keep following until you get to a spot where you can walk across to another walkway. Head to left. Go right to an area where there is a ladder and you can see three gaurds walking around ( some can be seen only with night vision).Go down the first ladder.If your trying to complete oppurtunity objective(place trackers on weapon crates) there is one down the second ladder and to the right. If not ignore second ladder and head right to a ladder heading up to launcher and end of mission.