Launching the commercial WorldView 4 Earth-imaging satellite for DigitalGlobe, a United Launch Alliance Atlas 5 rocket thunders away from California’s Vandenberg Air Force Base today at 10:30 a.m. local time (1:30 p.m. EST; 1830 GMT).

With the SpaceX scrub earlier this week and the time needed to convert the Eastern Range over to the Delta 4, liftoff of that rocket carrying an internationally-purchased military communications satellite for the Air Force has been bumped to Saturday evening.

A United Launch Alliance Delta 4 rocket will deliver the U.S. Air Force’s second GPS 3-series navigation satellite into an elliptical transfer orbit nearly two hours after liftoff from Cape Canaveral.