You may be thinking about the museum that's right on the road out to Chincoteague, near Wallops. It's on VA-175,just off to the right as you are heading out to Chincoteague. It's about 10 miles off of route 13, and its official name is the Goddard Space Visitors Center. Back almost 6 years ago, my husband and I spent about 2 hours there. It was rather unplanned but very, very enjoyable. One of the things that we enjoyed the most about the place was standing outside the front door of the museum and looking across the highway at the array of satellite dishes doing their thing.
Further on down, we were lucky enough to see two of the wild horses of Chincoteague. Like many little girls years before, I had read Marguerite Henry's Misty of Chincoteague, Stormy, Misty's Foal, novels set in the area. When you're there, if you see someone pulled over and looking into the forested areas, slow down and look too. You just may be as lucky as we were.
BTW, I think you're wise to cut Atlanta from this trip.