Video: Atlas 5 rolls out to launch pad with the Air Force’s AEHF 5 comsat (members only)

An Ariane 5 rocket emerged from its vertical assembly building Monday and rolled along dual rail tracks for a 1.7-mile (2.7-kilometer) journey to its launch pad at the Guiana Space Center on the northern coastline of South America, moving into position for blastoff Wednesday with four Galileo navigation satellites.

Giving every opportunity for the storm clouds to blow clear after a four-hour hold, the United Launch Alliance Delta 4-Heavy rocket counts down Thursday afternoon at Cape Canaveral until the clocks had to be halted for the day.

Riding nearly a million pounds of thrust, NASA astronaut Chris Cassidy and Russian crewmates Anatoly Ivanishin and Ivan Vagner rocketed into orbit April 9 from the Baikonur Cosmodrome en route to the International Space Station.