From Outscape Wiki
Ship Scanners are needed for every ship to get built. You cant research a new ship Blueprint with out a ship scanner put on it.
Normal Ship scanners operate like planetary scanners with a scanner range (the space outside the inner circle), It can only see fleets and labels them as UFO's
The sensor range (The inner circle), will show you at mouse-over the amount of ships in the fleet, the fleet name, and who owns it.
When a fleet is in sensor range you can take a look at what kinds of ships are in the fleet and the modules they have equipped.
There are also two specialised scanners that allow you to see cloaked ships and minefields the Cloak Detector and Mine Detector can only be equipped on a Corvette class ships. When you add these modules they have the effect of enhancing a ships sensor range not the scanner range to see mines and cloaked fleets.
This link takes you to the Planetary Scanners which operate just like ship scanners, but have increased range.