Live coverage: Atlas 5 countdown and launch journal

A 6.6-million-pound Apollo-era crawler-transporter rolled up the ramp to pad 38B on Tuesday and was positioned directly under the 3.5-million-pound Space Launch System rocket and its 11.3-million-pound mobile launch platform.

A hundred days after the last U.S. commercial resupply of the International Space Station by a Cygnus cargo ship launched atop an Atlas 5 rocket, the booster and freighter duo will do it again Tuesday.

A three-man crew departed the International Space Station on Sunday, concluding more than five months aboard the orbiting research complex and heading for landing in Kazakhstan. Undocking of the Soyuz MS-07 spacecraft occurred at 0916 GMT (5:16 a.m. EDT), and the trio landed on the Kazakh steppe at 1239 GMT (8:39 a.m. EDT).