Enlarge / The first Ariane 6 rocket is pictured inside the mobile gantry on its launch pad in Kourou, French Guiana. The gantry will wheel away from the rocket during the countdown Tuesday. (credit: ESA-S. Corvaja)

Europe’s Ariane 6 rocket is finally ready to fly, four years late but vital as ever for European governments backing the more than $4 billion project.

Set for liftoff from French Guiana, the new rocket will be Europe’s flagship launcher for the next decade, providing rides to space for European science probes, navigation satellites, and military payloads. Ariane 6 also has a toehold in the commercial market, with a contract for 18 launches to deliver satellites to orbit for Amazon’s Project Kuiper broadband network.

The first Ariane 6 rocket has a four-hour launch window opening at 2 pm EDT (18:00 UTC) Tuesday to depart the European-run Guiana Space Center in South America.