Snapshots from Atlas 5 launch

The operation comes a week after NASA conducted a so-called ‘confidence test’ on Feb. 12, which was the process of loading some liquid hydrogen on the rocket’s core stage.

The United Launch Alliance Delta 4 rocket, standing 217 feet tall and weighing 900,000 pounds, unleashes 1.8 million pounds of thrust from its main engine and four side-mounted boosters at 8:18 p.m. EDT Saturday (0018 GMT Sunday) to launch the ninth Wideband Global SATCOM satellite for U.S. military and allied communications.

Two astronauts floated outside the International Space Station early Friday for the first of four planned spacewalks to wrap up a complex multi-year job to replace 48 aging batteries in the lab’s solar power system with 24 more powerful lithium-ion units.