Is the range of a ship's sensors a hard limit? If not, how does this function mechanically and what is the true range limit?

As a specific example (minor, minor spoilers ahead), in the Trouble Brewing adventure, the PCs can scan the asteroid when they arrive. Success with this scan reveals the scout droid. A YT-1300 has a short sensor range while the scout droid has a medium range. Shouldn't the scout droid detect the PCs long before they can detect the droid? Even if they both had the same range, wouldn't they just discover each other simultaneously? I just don't see any situation (other than if the PCs somehow have a ship with long range sensors) where the PCs would be able to sneak past the scout droid, since the droid will always see them first.

My concern here is less about the specifics of Trouble Brewing and more with regards to how it will work for future adventures. It seems like this would make any sort of stealth approach with regards to starships effectively impossible. Is that the case?

Sensor range is the listed limit in passive mode in 360°. One band further in active mode but only in a single 90° arc.

So if the droid is in active mode and happens to be scanning in a different direction its quite easy to see it before it sees you.

Sensor range is the listed limit in passive mode in 360°. One band further in active mode but only in a single 90° arc.

So if the droid is in active mode and happens to be scanning in a different direction its quite easy to see it before it sees you.

Is that in the rules somewhere?

Edit: Found it. Page 227. Thanks.