Well, when we get back we can add archaeological studies to our skills.

( kidding. though even without technology they wouldn't be too out of it, after all in first contact situations or even observing pre-warp civilisations they've had to be able to survey a planet without any traces or technology at times )

The star map will be one thing that can help us. Though for the moment a lot of our observations will be visual: daylight hours, seasons, at least what we can assume on comparison.