I don't have a good screenshot handy, but you get there from the prison portion of the facility, from the upper level of that two-tiered room with all the cells. Over on one side there's an elevator in one of the rooms. Behind the elevator are some broken boards that lead to a tiny room that just gives you some lines about Lea. Take the elevator up and it will lead to that room you're trying to get into, which has a few items and a shortcut back to the Stargazer.