Photos: Atlas 5 on the pad at sundown

This is the ascent timeline to be followed by the United Launch Alliance Atlas 5 rocket in launching the Mobile User Objective System satellite No. 4 on Wednesday at 5:59 a.m. EDT.

Gearing up for a predawn blastoff July 31, launch crews have positioned a Delta 4-Heavy rocket in the starting blocks on a seaside launch complex at Cape Canaveral as engineers inside a tightly-controlled clean room a few miles away put the final touches on a NASA probe that will travel closer to the sun than any mission before.

In addition to carrying an Air Force electric propulsion thruster test, a materials research investigation sponsored by NASA’s Marshall Space Flight Center will be flying aboard the X-37B miniature spaceplane later this month.