Amazon is getting ready to launch two test satellites for its Project Kuiper satellite internet constellation, built to compete with services like SpaceX Starlink and OneWeb. In a press release on Wednesday, the company says the prototypes, charmingly named Kuipersat-1 and Kuipersat-2, will be riding into orbit on a Vulcan Centaur rocket from the United Launch Alliance (ULA) in early 2023.

The company says the launch will let it perform tests on its satellite network technology with data from space and that the data will “help finalize design, deployment, and operational plans for our commercial satellite system.” The timeframe marks a slight delay from Amazon’s original plan; last year, the company announced it would launch the prototypes in Q4 of 2022, using a completely different rocket from a company called ABL Space Systems.

Early 2023 isn’t too far away, but there are still a lot of things that have to go right for the launch to happen on schedule. For one, Amazon needs to actually finish building the satellites, which its press release says will be completed later this year. The rocket also isn’t done yet — ULA said in a press release on Wednesday that it expects to have Vulcan fully assembled by November and tested by December — for now, though, it still has to install the engines. It’s not exactly a proven launch platform, either; this will be the rocket’s first flight.

Both companies have deadlines to meet. As The Washington Post points out, ULA has to launch Vulcan twice before Q4 2023 to prove that it’s reliable enough to carry out missions for the US Space Force. Meanwhile, Amazon has to launch half of its satellites by 2026 to keep its FCC license. That’s further away than the end of next year, but given that Amazon’s constellation is set to be made up of 3,236 satellites, that’s going to require quite a few launches in the next few years. Thirty-eight of them are set to use the Vulcan, while several others will be with rockets from Arianespace and Jeff Bezos’ Blue Origin. (Fun fact: the BE-4 engines that Vulcan uses are also from Blue Origin.) Notably absent from its list of partners is SpaceX, which other satellite providers like Lynk and AST SpaceMobile have used to launch equipment into space.

Once its fleet of satellites is in orbit, Amazon says its plan is to “deliver fast, affordable broadband to unserved and underserved communities around the world.” It also has an agreement with Verizon to act as a backhaul for remote LTE or 5G cell towers.