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.

An Ariane 5 rocket launched Tuesday with the Arabsat 6B and GSAT 15 communications satellites to broadcast television across the Middle East, North Africa and Central Asia and link India with telecom and navigation services. Liftoff from Kourou, French Guiana, occurred at 2134 GMT (4:34 p.m. EST).

United Launch Alliance’s first Vulcan rocket was filled with methane and liquid oxygen propellants at Cape Canaveral last week for a tanking test, but managers decided to move the rocket back inside a hangar for a few adjustments before proceeding with an engine test-firing.