Live coverage: Atlas 5 countdown and launch journal

Riding the rails to the launch pad Wednesday morning, the Atlas 5 rocket was rolled out to Cape Canaveral’s Complex 41 for liftoff Thursday night to deploy four NASA satellites that will probe Earth’s magnetosphere for a high-priority research project.

The satellite awaiting launch early Saturday from California aboard the final flight of the venerable Delta 2 rocket should allow scientists to more precisely track changes in our planet’s ice sheets, using six green laser beams to chart the height and slope of polar ice and glaciers, providing a key input into climate change research.

A day-and-a-half before its liftoff with a U.S. Air Force communications satellite, a United Launch Alliance Atlas 5 rocket rolled out to its launch pad at Cape Canaveral on Monday morning.