At the beginning of *Thor*, Jane Foster has brought Darcy and Erik out in the middle of the desert because she's been investigating "atmospheric disturbances" that have had a regular, highly predictable pattern, and the next one is supposed to happen right now. And then the Bifrost opens and drops Thor in their laps.

And then we see how Thor ended up there, and it was a one-off event, not at all periodic or mathematically predictable. So that makes me wonder: what were the previous events that established the pattern that led Jane to (correctly) believe there would be another one at that exact place and time? She makes it sound as if they were recent, but on the Asgard side of things we have no indication that there's recently been regular, periodic travel between Asgard and Earth. Quite the opposite, in fact.