Subject: Can failed NASA missions be launched again?

What happens to the science team and spare equipment when missions fail, like 
CONTOUR?  Does NASA even keep spare models around to trouble shoot when active 
missions face problems, for example, when Voyager 2’s camera was sticking 
while approaching Uranus?  A spare camera highlighted the fact that planetary 
scientists were moving the camera too much.
Is it possible to launch the back up hardware as a second mission, assuming 
that the error has been detected, reengineered and tested?  How much would it 
cost to launch failed missions a second time?  $50 million per Delta III 
rocket to reach the Moon and near-Earth asteroids, and another $50 to 
integrate the spare components into a spacecraft?
Should missions include a second launch option while in the planning and 
budget process?  
Thank you for your time.

Re: Can failed NASA missions be launched again?