The sensor system allows the Captain to see enemy ships during the battle. enemies can also only be targeted by the weapons systems while they remain within sensor range.
The range of sensors is dictated by the amount of power they receive.
While in the sensors, the engineer can suggest the next target to the Captain. This is however just a suggestion, and can be ignored if the Captain decides there are more important targets, or the suggested target is lost. The current target cannot be changed unless it is destroyed or lost.