The space agency is also celebrating 10 years of continuous human presence at the International Space Station, where Discovery is headed.
On Nov. 2, 2000, three men moved into the young space station. Astronauts and cosmonauts have been there ever since, living and working more than 200 miles above Earth.
Discovery will bring six visitors as well as a load of supplies, including a humanoid robot. Forecasters say there is a 70 percent chance that the weather will cooperate Wednesday afternoon for liftoff.
NASA's oldest surviving space shuttle first rocketed into orbit in 1984. This will be its 39th and final journey.