PARIS — The European Space Agency stepped up to be Arianespace’s first customer for the next-generation Ariane 6 rocket, while keeping Soyuz as a backup option.

Signing the contract on behalf of the European Commission and the European Union, ESA agreed to launch four Galileo navigation satellites two at a time on Ariane 6 rockets. The missions will both use the Ariane 62, the lighter version equipped with two side-boosters, and will launch from Europe’s Guiana Space Centre in French Guiana in late-2020 and mid-2021.

ArianeGroup, formerly Airbus Safran Launchers, is building the Ariane 6, with ESA overseeing the rocket’s procurement and architecture. Arianespace has a first-ever demonstration flight of the Ariane 6 on July 16, 2020.

“Arianespace is especially proud to have won this first launch contract for the Ariane 6 from its loyal customers and partners, the European Commission (DG Growth) and ESA,” Stéphane Israël, Arianespace CEO, said in a Sept. 14 statement.

ESA’s contract includes the ability to rely on Soyuz, also launching from the Guiana Space Centre, if the Ariane 6 is not able to complete the mission. Arianespace launched 14 of the 18 Galileo satellites currently in orbit using Soyuz rockets; an Ariane 5 launched the most recent four.

The Ariane 6 and Vega C rockets are intended to replace Arianespace’s existing launch family of the Ariane 5, Soyuz and Vega, assuring European access to space with vehicles that can compete more effectively with SpaceX and other rising launch competitors.

Arianespace has another four-satellite Galileo launch using the Ariane 5 “Evolution Storable” version in December, followed by another in summer 2018.

Galileo satellites weigh roughly 750-kilograms each and operate in a 23,000-kilometer medium-Earth orbit. The European Union owns Galileo.