This is a little late, but I thought people here might care. Last week, NASA officially created the Planetary Defense Coordination Office, which pretty much does what the name implies, though they're more in the business of asteroids and Near Earth Objects than alien invasions. Lindley Johnson, the head of the new office, holds the title of Planetary Defense Officer. How nonchalantly badass is that?
http://www.jpl.nasa.gov/news/news.php?feature=4816