How did they know they were 50,000 years in the past and how did they get back..............to earth on time?
Not sure on that one. But they somehow made it back through the portal in orbit after a few hours or days spent 50,000 years in the past. They didn't land, they just orbited.
Who put a time/space portal in orbit I don't know. I heard there was a portal around Mars' orbit somewhere too.
If it really happened it's been like 50 years since it happened - new technology would have enabled NASA to explore the portal up in orbit more and probably sent tons of rovers and shit 50,000 years back in time.