This afternoon, Europe will launch its 100th Ariane 5 rocket, a historic achievement for the nearly 20-year-old vehicle design. Launching from Europe’s South American spaceport in French Guiana, the Ariane 5 will put a pair of communications satellites into a high orbit above Earth. And if all goes well, it will mark the 300th overall flight for the three-vehicle family of Arianespace, the launch provider overseen by the European Space Agency.

First introduced in 1996, the Ariane 5 has been the premier heavy-lift vehicle of Arianespace, launching numerous large communications satellites, as well as space observatories and cargo vehicles to the International Space Station. The rocket is also responsible for launching Europe’s Rosetta mission, which sent a spacecraft to a comet and deployed a lander onto the object’s surface.

First introduced in 1996, the Ariane 5 has been the premier heavy-lift vehicle of Arianespace

In its early years, the Ariane 5 suffered from a handful of failures, but from 2003 to 2017, the vehicle boasted 100 percent successful consecutive launches. However, that streak came to end this January, after the vehicle suffered a partial failure during flight; the rocket accidentally veered off course due to some incorrect numbers that were inputted into the vehicle’s guidance system before takeoff. However, the Ariane 5 was still able to deploy the two satellites it was carrying at the time — just in a lower orbit than planned.

The Ariane 5 has a few significant missions ahead, most notably launching NASA’s upcoming James Webb Space Telescope sometime around 2021. But the rocket is closing in on retirement. Arianespace has been developing the vehicle’s successor, the Ariane 6, which the company hopes to enter into operations as early as 2020. The plan is for the Ariane 6 to eventually replace the Ariane 5, with the latter vehicle phasing out by the end of 2022, according to Ars Technica.

For today’s flight, the Ariane 5 will be launching two satellites on a path 22,000 miles above Earth. One of those probes is Horizons 3e, which will be operated by two partnering companies, Intelsat and SKY Perfect JSAT. Horizons 3e is meant to provide broadband services to areas in the Asia-Pacific region. Meanwhile, another satellite called Azerspace-2/Intelsat 38 will also be going up on this flight. Operated by Intelsat and Azercosmos, this probe will provide direct-to-home services in Europe, Asia, and sub-Saharan Africa.

The launch window for today’s flight opens at 5:53PM ET and extends until 6:38PM ET. The full flight, from takeoff until the last satellite’s deployment is expected to last around 42 minutes. Arianespace will live-stream the mission, with coverage beginning around 20 minutes before liftoff; check back then to watch the flight live.