AFAIK, and without breaking any Australian Laws pertaining to my past employment (s.70 Commonwealth Crimes Act), I guess that Pine Gap is part of the global signal processing systems that the USA utilises.
I never worked there, but did work with people who did on Term Postings (3 yr. terms).
Most of them loved Alice Springs and the surrounding environment, as it is a unique place to live and so much different to where you usually hail from . But the isolation of the town from anywhere else, can be a problem to those that hail from very urban envirnoments, things are not so readily available and Alice's isolation can play havoc to families that have a family member stationed there on Term Posting. Relationships can suffer too, while although one partner may be earning a fortune in all sorts of extra Allowances etc. the other partner's career is on hold as employment (and in the case of family members of US personnel, may be prohibted from working under immigration laws?) is hard to find. It must be emphasised that it is a decent commercial flight to anywhere that resembles a city (Darwin or Adelaide are smallish Cities but urban enough for those wanting their Lattes and muffins!), and I was told that some things can be frighteningly expensive in Alice because of the transportation costs to get them there.
If the Posting is approached properly by the family unit it can expose them to a lifestyle that is quite different to what they'll experience in the future. But if you have a kid who resents the move or a wife who begrudges becoming a housewife instead of persuing her career as a lawyer like she did back home, then there could be trouble.
There is, however, a distinct need to keep a high security awareness both while at work and away from it, even years after you leave there, mostly because folks are damed curious about the place and will ask you stupid questions that you either don't know the answer to, or you can't talk about. In that respect, your friend, in working there, should consider themself a very highly regarded person by their Govt. to be stationed there.
Pine Gap was built during the Cold War, and it's uses have been subject to all sorts of conjecture and protests from various groups within Australia. At one stage, in 1975, it was alleged that Pine Gap had a hand in relaying messages that bypassed the Australian Govt.'s eyes and helped to bring about the downfall of the then Prime Minister, Gough Whitlam , who was not a fan of the base (he was against it because he believed it made Australia a nuclear target in the event of full scale war.). In those very Cold War days it might well have been a designated target by the Communists, who knows? :dontknow:
You are right in paralleling Pine Gap to the US's Area 51. That's because of the tight security - which is essential, and something I firmly uphold their (US and Australian Govts) right to have. But shady shenanigans and disappearing aliens etc. that is part of the infamy of Area 51, is not the case here.