United Launch Alliance has completed stacking of the major elements of the Atlas 5 rocket assigned to power NASA’s Perseverance rover toward Mars, but the mission’s launch date has been pushed back three days to July 20 after teams repaired an issue with a crane in the Atlas 5’s assembly building.

These photos captured on the eve of launch show a United Launch Alliance Atlas 5 rocket standing on its launch pad at Cape Canaveral Air Force Station, ready for blastoff on the U.S. Air Force’s AFSPC 11 mission with three satellites on-board.

United Launch Alliance’s first Vulcan Centaur rocket completed a critical test-firing of its Blue Origin-built BE-4 main engines Wednesday night, clearing one of two remaining technical hurdles before the launcher is cleared for its inaugural flight later this year.