Live coverage: Two satellites lift off aboard Ariane 5

European engineers test-fired the world’s most powerful present-day single-segment solid rocket booster Monday in French Guiana, clearing a major development hurdle for the Vega-C and Ariane 6 launchers set for debuts in 2019 and 2020.

The Italian PRISMA Earth observation satellite is set to ride a Vega launcher into a 382-mile-high (615-kilometer) orbit Thursday night from French Guiana on a mission that will take less than one hour from liftoff until spacecraft separation.

The next flight of Europe’s heavy-lift Ariane 5 rocket, set for July 28 from French Guiana, will carry a record payload of three multi-ton satellites toward geostationary orbit, including a pair of U.S.-built commercial communications payloads and Northrop Grumman’s second robotic satellite servicing spacecraft.