Shuttle tribute posters.

So what is your favorite space shuttle?  With the retirement of the shuttles coming up in 2 or maybe 3 more flights, we'll have nothing manned from KSC after that.  Don't get me started on that right now!
NASA has published some really snazzy posters of our shuttle fleet.  The photo of the shuttle with highlights of their finest missions and all the mission patches around the shuttle. 
Here is the Discovery poster.  Can you figure out the significance of the 2 shaded looking missions in the middle?

 | Full set of mission posters here (Universetoday.com)  |