Space Shuttle 2: Even better!
#28
It's really simply a photo op. The Enterprise has been out at the Air & Space Udavr-Hazy center, and they've decided to replace it with the Discovery which has actually been in space (a lot). So as they were moving the Enterprise out and the Discovery in, it was just a good chance to make an event out of it and celebrate the program as it comes to a close.
The Enterprise looks so clean because it never went into space (and it's been restored). It was the prototype used for flight testing, but without engines or working heat shields. As it's being replaced here by the Discovery, the Enterprise is being moved up to NY next week, eventually to the Intrepid.