A bold statement to start: Amazon’s Leo broadband push is reaching a new height with a long-awaited Atlas 5 launch that will finally place the 180th Leo satellite into low Earth orbit. But here’s where it gets controversial: the timing, weather, and ork surrounding its deployment could shift the entire pace of the constellation’s rollout.
United Launch Alliance (ULA) is prepping for its final mission of 2025, a predawn ride for an Atlas 5 carrying 27 satellites to power Amazon’s newly branded Leo network. Liftoff is set from Space Launch Complex 41 at Cape Canaveral Space Force Station at 3:28 a.m. EST (08:28 UTC), within a 29-minute window. The rocket will head northeast after leaving the pad.
This mission, known by ULA as Amazon Leo 4 and by Amazon as Leo Atlas 4 (LA-04), marks the fourth Atlas 5 launch for the venture, which previously operated under the Project Kuiper banner.
Spaceflight Now will provide live coverage starting about an hour before liftoff.
ULA initially skipped Monday’s launch opportunity due to high winds, leaving little hope for acceptable weather. The 45th Weather Squadron, however, predicted a strong forecast for Tuesday morning, with a 95 percent chance of favorable conditions within the launch window.
On Saturday morning, the team rolled the 205-foot-tall (62.5 m) rocket, AV-111, from the Vertical Integration Facility toward the pad for a final 0.5-kilometer journey. It was installed onto the launch pad piers and secured in a move called “hard down” at 11:51 a.m. EST (16:51 UTC). Later that day, 25,000 gallons of rocket-grade kerosene were loaded into the first-stage booster.
ULA will complete fueling with liquid oxygen and liquid hydrogen in the hours leading up to liftoff on Tuesday.
The Atlas 5 in the 551 configuration uses a central RD-180 engine surrounded by five solid rocket boosters. The boosters will separate roughly two minutes into flight.
About 4.5 minutes after launch, the Atlas core will separate, and the Centaur 3 upper stage’s RL10C-1-1 engine will ignite for a burn of just under 13 minutes. A deployment window for the Amazon Leo satellites starts around T+20 minutes and spans about 15 minutes.
Launch controllers will oversee a final Centaur burn to deorbit the stage after satellite deployment.
Closing out the year
2025 marked the formal rollout of Amazon’s operational satellites. With Tuesday’s launch, the fleet will total 180 Leo satellites orbiting Earth, launched across four Atlas 5 missions and three SpaceX Falcon 9 missions. Amazon has a deadline to deploy half of its planned 3,200-satellite network by July 31, 2026, though the company may seek extensions or waivers. LA-04 will bring 2025’s Leo deployments to a close.
In early December, Amazon announced that components for the first Ariane 64 rocket had shipped from Bordeaux, France, headed to French Guiana for a 2026 kickoff launch. The company committed to 18 dedicated Ariane 6 missions, each carrying 32 satellites.
The satellites, manufactured in Kirkland, Washington, were moved to Amazon’s satellite processing facility at NASA’s Kennedy Space Center before heading to French Guiana.
Other notable milestones this year included rebranding the constellation from Project Kuiper to Amazon Leo in early November, described by Amazon as a straightforward nod to the low-Earth-orbit network powering its services.
In late November, Amazon unveiled Ultra, a gigabit-speed user terminal. The enterprise-grade antenna is designed to deliver top-tier performance for demanding private and public sector applications and was offered to a select preview group.
