TL;DR: Jane Foster was not seeing the Bifrost open & close. She had instead found a way to detect the pathways along which it opens - the "branches" of Yggdrasil.
We know from the events of the film that the Bifrost Bridge is only opened when needed. We also know that transportation using the bridge results in an obvious pattern on the ground. However, the events being monitored by Foster were repetitive, predictable, and did NOT leave any observable effect on the ground. Rather, she was looking UP... into the stars.
Jane Foster described her research as astronomic anomalies. As Thor explains to her, she is actually seeing Yggdrasil, the World Tree:
THOR: You must do this. You must finish what you've started.
THOR: Because you're right. It's taken so many generations for your
people to get to this point, but you're nearly there. You just need
someone to show you how close you really are.
THOR: Look - your ancestors called it magic. You call it science. I
come from a place where they're one and the same thing. (begins
(Shot of notebook. We recognize that Thor is drawing the branches of Yggdrasil as she
looks on, amazed and intrigued.)
JANE: What is it?
THOR: This is how my father explained it to me. Your world is one of
the Nine Realms of the Cosmos, linked to each other by the branches of
Yggdrasil, the World Tree. Now, you see it every day, without
realizing. Images glimpsed through - what did you call it? - (checks
her notebook) - this Hubble Telescope. So, Nine Realms...
They look at each other. She nods. They smile. This is going to be a long night...
With this information in mind, the only possible event that Foster could be seeing is the pathways themselves, possibly pulses of energy along the branches of the World Tree. This concept of energy pulsing along pathways - similar to a nervous system - is consistent with other images we've see of Yggdrasil in the MCU, and even with the "frozen" effect we see when Loki freezes the overloading Bifrost Bridge:
As for Foster "predicting" where Thor would land, it's more likely that - by tracing the pathways - Foster had found one of the locations where Yggdrasil intersects with Earth. As a result, she was already at the location when Thor was casually cast to Earth by his father Odin.