Let me be the first to say that this is a silly question and tiny mistakes like this are made all the time, but I was just re-watching a few Voyager episodes. In Homestead (season 7, episode 22), just before the opening credits, Chakotay interrupts the party to tell Nelix:
Long Range sensors have detected several hundred life signs, 4.9 light years away. They're Talaxian.
I don't think sensors can tell the difference between species from 4.9 light years away. If they can, are there any other references to sensors being that accurate?
This could be explained away by having talked with these Talaxians, or maybe detecting their ships’ signatures as Talaxian, but neither explanation was offered. The wording of the show implies the sensors could tell they were Talaxian from 4.9 light years away.
Is that a bit of an error, or are there other examples of sensors being that effective that far away?
Update: Later in the show they had 7 of 9 explain to the visiting lady Talaxian that her sensors were very powerful, so it was probably explained as a 7 of 9 astrometrics update, but also in the show they had trouble tracking the ship after it crashed so . . . I'm going to go with bad writing on this one.