New Mexico Museum of Space History. Took my wife and 14-year-old son to see it. Very interesting museum exhibits! Lots of decommissioned hardware to view; in the front of the building they have the John P. Stapp Air & Space Park, which exhibits several missile systems, and the Little Joe II rocket.
There are mockups of the Mercury, Gemini and Apollo capsules.
Inside, there's lots of hardware and photo documentation of the history of space travel. There's a neat Space Shuttle landing simulator the kids will enjoy.
Well worth the time inside. My back still aches from the 3 3/4 hour drive from Belen.
BTW Check out your local library for a free pass! There's a pass system that allows you entry for several museums and attractions throughout Nuevo Mehico. We saved $16 by using it!