Elon Musk's SpaceX Reaches Milestone With Launch Of Falcon 9 Spy Satellite 

Mission involved booster landing.

SpaceX has reached a new milestone on May 1 by launching a top-secret satellite and then bringing back its Falcon 9 booster for a touchdown at Florida landing zone. 

This satellite was launched for the National Reconnaissance Office (NRO), which is a member of the US intelligence community and an agency of the United States Department of Defense.

SpaceX is an American aerospace manufacturer and space transport services company headquartered in Hawthorne, California. Elon Musk is company's founder.