Is NASA working to warn us about asteroids that might hit the Earth?

The space agency is developing a better asteroid-detection program but is about a decade behind in meeting a congressional deadline. NASA officials say they need a telescope in space to improve tracking. Most large asteroids that may trigger a global catastrophe already have been found and tracked, officials said, and an impact within the next several centuries is unlikely. But smaller objects can still do damage, and although they are less lethal, they are harder to track and arrive more often.