Running through a practice countdown to check systems before launching a NASA sample-return probe to Asteroid Bennu in exactly two weeks, an Atlas 5 successfully completed its Wet Dress Rehearsal today.

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.

A United Launch Atlas 5 rocket is set to launch the U.S. Air Force’s fifth Advanced Extremely High Frequency communications satellite from Cape Canaveral. This timeline shows the major mission events planned over a nearly six-hour flight to an optimized geostationary transfer orbit.