It works automatically when you get close enough to the body for the scan to start to make it no longer "unknown". It generates additional info and more credits when you sell the data.
It does work automaticly, but if you only have a basic scanner or an intermediate scanner, you eill still have to fly around a system to locate all of the objects in the big systems.
Especially if you get it for free on one of the Kickstarter options ;-)
One of the kickstarter options if you invested more than about £90 I think is that you get to start as an explorer in a Cobra with an intermediate DS and a DSS and a 20LY frameshift drive - in fact if you work it out on value it's by far the best kickstarter ship to take. However, all the equipment is classed as loaned so you can't sell it for a million credits or whatever, but even so, it's still some valuable equipment for free.
Ok so the surface scanner doesn't replace the D-scanner like I hoped it would. Found out the hard way, although I was suspicious that was how it would be. It works in tandem with it. And I don't want to go shieldless in the Sidey. Now to decide between the Hauler or the Adder, but I am going to miss the little Sidewinder, we've seen so many sights and run from so many pirates together.