Endeavour soared to a landing at NASA’s Kennedy Space Center early June 1, ending an ambitious final mission that equipped the International Space Station with the Alpha Magnetic Spectrometer (AMS), a $2 billion marquee science project, while leaving the space shuttle program on the brink of a long-anticipated retirement.

Endeavour rolled onto Runway 15 at 2:35 a.m. EDT, with Mark Kelly, commander of the 16-day STS-134 mission, at the controls.

Within an hour, Atlantis was parked at Launch Pad 39A, where preparations are running ahead of schedule for the July 8 launch of the shuttle program’s final voyage, the 12-day STS-135 supply mission to the station. The 7-hr. rollout of Atlantis was another final milestone for the three decade-long shuttle program.

“It’s great to bring Endeavour back in great shape,” Kelly noted from the runway, where he, pilot Greg Johnson and crewmates Mike Fincke, Drew Feustel, Greg Chamitoff and Roberto Vittori were greeted by NASA Administrator Charles Bolden and other agency dignitaries. “It looks like it’s ready to go do another mission.”

Endeavour follows Discovery into retirement. By early next year, both orbiters should be de-serviced; Endeavour then will be on its way to the California Science Center and Discovery to the National Air and Space Museum’s Udvar-Hazy Center in Chantilly, Va.

Before Atlantis takes a similar path for display at KSC, the four-member STS-135 crew will haul more than 10 tons of equipment to the orbiting science lab and return with more than nine tons of gear, closing out 12+ years of station construction and outfitting.

“Assembly complete is a pretty big milestone,” said Bill Gerstenmaier, NASA’s associate administrator for space operations, during a post-landing news briefing. “But I don’t want to focus on assembly complete. I want to focus on the other side, which is the need to begin utilization in earnest.”

Endeavour’s delivery of the AMS—which is attached to the station’s solar power truss to search for primordial antimatter, dark matter and other high-energy particles that shape cosmic evolution—will advance that objective, according to Gerstenmaier.

“It’s a world-class instrument, and the amount of data they are receiving is phenomenal,” he said of the 16-nation collaboration.