You can go, you need to be working at one of the research bases, either as a scientist, technician, contractor, etc. I used to get job offers when I was getting out of the Army. I think it’s like a 6 months on 6 off kind of thing, unless circumstances leave you stuck for longer periods.
Non employees can visit but it’s usually for media stuff, or you’re famous/important enough that one of the governments gets you a temporary visit. They always need people for upkeep, water, plumbing, electrical, cooks, and other shyt like that.
It’s like any place that needs a permit, and the permits are usually for liability, environmental health, accountability, etc.
Not knocking your answer, just putting this out there for anybody curious. Photographers, biologists, and all kinds of random freelancers go all the time. It’s rare for any active military to have to go there for any reason at all. If any military is there at all its just n small numbers to support researchers or get flight time doing cargo airlifts/rescues or some shyt.