Why did Starfleet expose themselves so easily to new species during Deep Space Nine?

Question

On Star Trek: Deep Space Nine, in Shadowplay (season 2, episode 16,) Dax and Odo transport themselves to a planet’s surface. There they find a species which they have never met before. In Battle Lines (season 1, episode 13) they travel within sensor range of some satellites orbiting another planet, potentially exposing themselves to the planet’s inhabitants.

In other Star Trek episodes, we previously saw that, when meeting new species who had not yet developed warp travel, Starfleet officers would go undercover to avoid exposing themselves, so as not to interfere with the normal development of the society. (For example, Who Watches the Watchers in Star Trek: The Next Generation).

Shouldn't they always go undercover as to not interfere with the normal development of the species?

Answer 1

In Battle Lines, they’re investigating the planet in question because they picked up a subspace signal. That presumably suggests that the civilisation in question is a space-faring one, meaning the risk of infringing the Prime Directive was small. As it turns out, the species was at least space-faring enough to be using a moon as a penal colony, so presumably the Prime Directive wasn't actually broken.

The incident in Shadowplay looks less forgivable, but there are still extenuating circumstances. They detect omicron particles on the planet, and omicron particles are super-rare. They would pique the curiosity of any science officer worth their salt, so some degree of rushing off to check them out without rigorously scanning for potential native life forms is understandable.

Even when Dax realises that they’re coming from a village, the fact that they’re omicron particles again presumably suggests that the society is reasonably likely to be space-faring — which, spoiler alert, turns out to be true. Given what we learn about the “village” and its “inhabitants”, it’s even possible that Dax had checked sensor readings, and seen no evidence of an existing civilisation in the area.