4:20pm ET Update: A Falcon 9 rocket lifted off at the end of its launch window on Tuesday afternoon, and delivered a GPS satellite into a good parking orbit. The spacecraft was due to deploy from the Falcon 9 rocket’s second stage about 1 hour and 29 minutes after liftoff.
After dropping off the second stage, the first stage descended back toward the Earth to successfully land on the Just Read the Instructions droneship. SpaceX now has five used first stages available for additional missions.
Original post: On Tuesday, SpaceX will attempt to launch a 3.7-ton Global Positioning System (GPS) satellite for the US Air Force. This GPS III launch is scheduled to occur on a Falcon 9 rocket between 3:55pm ET and 4:10pm ET (19:56-20:10 UTC) from Cape Canaveral Air Force Station in Florida.