The radar 'minimap' gives a range of about 50m - if the enemy moves beyond that range, does this mean they won't see you if you emerge from hiding? or are you 'out of sight, out of mind'..?
It’s not just sight. Sound also matters. Alarms alert the entire base. They can see your ship arriving if you land too close. Being behind stuff helps although it won’t make them forget you once aggro’d, unless you remain unseen for quite some time.