Weather forecasters expect a 70 percent chance of favorable conditions at Cape Canaveral for liftoff of a United Launch Alliance Delta 4 rocket Thursday with a GPS navigation satellite, marking the last flight of the Delta 4’s single-core variant after 29 flights since 2002.

Riding the rails between its assembly building and the launch pad, an Atlas 5 rocket topped with a clandestine national security satellite was rolled out this morning for Thursday’s liftoff at 4:07 a.m. EDT (0807 GMT).

United Launch Alliance teams at Cape Canaveral hoisted a Centaur upper stage on top of an Atlas 5 rocket Friday at launch pad 41, completing the initial build-up of the launch vehicle slated to carry Boeing’s Starliner crew capsule into space in December on an unpiloted test flight to the International Space Station.