After several weeks of delay due to defective equipment and bad weather, the United Launch Alliance is scheduled to launch its most powerful missile from Cape Canaveral, Florida. Lifting a secret spy satellite for the National Reconnaissance Office. The mission is finally ready to fly a full month after the first missile launch attempt, which was aborted just three seconds before takeoff.

The missile launched on the ULA mission is the Delta IV Heavy, a gigantic vehicle consisting of three missile cores attached to each other to provide additional thrust. It is one of the most powerful rockets in the world, although it falls short of the power packed into the Falcon Heavy. ULA does not fly Delta IV Heavy often, because it is an expensive vehicle, but the company does use the missile for large and heavy satellites heading into ultra-high orbits.

The missile’s payload is the NROL-44, and like all NRO missions, its purpose is hidden in secret. The office simply notices “NROL-44 supports the NRO’s overall national security mission to provide intelligence data to top US policymakers, the intelligence community and the Department of Defense.” ULA has already launched 29 missions for the NRO, many of which required Delta IV Heavy.

ULA was ready to launch NROL-44 in the early hours of the morning of August 29. The ULA was back all the way only seconds before takeoff, with the Delta IV Heavy’s main engines igniting briefly. However, the engines quickly stopped and the missile remained stationary on the launch pad. The ULA later learned that a piece of ground equipment had failed, resulting in a miscarriage. It took the company a few weeks to replace defective equipment.

Other issues with equipment on the launchpad delayed the launch time again, but ULA hopes to take off this week. Unfortunately the weather was not good, with bad conditions delaying attempts on Mondays and Tuesdays. But finally, there’s a 70 percent chance the weather will team up for the launch tonight – so maybe today is the day.

Delta IV Heavy is scheduled to take off Tuesday at 11:54 PM ET from the ULA launch site at Cape Canaveral Air Force Station. For ULA Blog launch It will start at 3:15 PM ET, and will webcast at 11:34 PM ET, for anyone still awake and hoping to get a launch in the middle of the night.

Update September 30th, 3:00 p.m. ET: This post has been updated from an old post, after several launch delays.