Watch It Live: Delta Launch Set For 4:34 a.m.

The countdown to the planned launch of a Delta II rocket is continuing at Cape Canaveral Air Force Station and all systems are go for an on-time liftoff.

The 12-story Delta II rocket and its payload -- a Navstar Global Positioning System spacecraft -- remain scheduled for launch at 4:34 a.m.The spacecraft was placed on internal power around 4:08 a.m.

Engineers are topping off helium and nitrigen pressure within tanks aboard the first and second stage. The gasses are used to maintain proper pressures within the tanks as propellant levels are exhausted by spacecraft engines.