That's a Longbow variant iirc... and just like Steve says, it can hover below line of sight, pop that sensor above what it's hiding behind and scan the battlefield... And with the latest Hellfires, they can even fire them from concealment as the missile streaks up, acquires the target and then goes down for the kill...
Oh, and as a geeky aside, the Longbow is the first helicopter to have networking ability to other Longbows, passing target data to other choppers that don't have a target acquired and guiding their missiles in...
Oh yes, I do like 'em.