My guess is that you may be seeing sun-synchronous satellites. If you look up the NASA A-train, you will find a good example of a sun-synchronous satellite constellation. Their orbits are north-to-south and south-to-north (depending on the time of day), and they pass over the same spot of the Earth at the same time of day. Satellites are easiest to see at twilight, when their altitude allows them to still be in full sunlight, but the surface is already in shadow. You can search out online applications which show where the constellations are at any given time and CelesTrack (https://celestrack.com) has orbit data which are publicly available (at least for the unclassified vehicles) and so does Space-Track (https://www.space-track.org/auth/login). I am not sure if there is a program or app developed which lets you know what satellites might be visible at a given location, but I wouldn't be surprised if someone has already written such a thing in Java, Python, R etc. I hope that helps.