This might fit the bill of what you're considering.
From the new CGI model of the upcoming remastered Star Trek...
I'm guessing that little doohickey that many of us never knew was there until very recently is now canon, and yes, I will be including it into the plans at some point.
Looks to me like a directional sensor, for high level sensor scans. Probably only has a relatively short range (no further than. say, standard orbit over a Class M planet to just below the surface.