The shuttle Atlantis astronauts left the International Space Station early Tuesday, unsure when another U.S. spaceship will reach the outpost.
One of the last things they did aboard the station was to add a sticker with their mission emblem onto a wall displaying a collection of insignias from 36 previous shuttle crews.
The next patch on the wall won't be a shuttle crew's, Atlantis commander Chris Ferguson said during a farewell ceremony on Monday. It could be Boeing, or SpaceX, or Blue Origin — any one of a number of companies working on commercial space taxis.
The first one to reach the outpost with U.S. astronauts will have a prize waiting. The Atlantis crew left behind a small American flag which flew on the first shuttle mission in April 1981.
NASA wants the next crew to reach the station aboard a U.S. rocket to retrieve the flag and bring it back to Earth, so that it can fly again on a NASA ship that’s headed into deep space, the follow-on mission to the shuttle and station programs.
"The space station has enabled us to speak the same language in space," Ferguson noted, a reference to the international flavor of the orbital outpost, which was built over the past 12 years by partnership that included the United States, Russia, Europe, Japan and Canada.
The shuttle fleet, which is being retired after Atlantis returns to Earth, did the bulk of the launching and assembly of the 1 million pounds of hardware that comprise the station.
"What a generation can accomplish is a great thing," Ferguson said, as Atlantis pulled away to begin the two-day ride back home.
"From our unique vantage point right here perched above the Earth, we can see the International Space Station as a wonderful accomplishment. It was born at the end of the Cold War, it's enabled many nations to speak (as) one in space.
"As the ISS enters an era of utilization, we'll never forget the role the space shuttle played in its creation. Like a proud parent, we anticipate great things to follow from the men and women who build, operate and live there. From this unique vantage point, we can see a great thing has been accomplished. FarewelI, ISS. Make us proud," he said.
The shuttle is due back at the Kennedy Space Center at 5:56 a.m. EDT Thursday.
(Shuttle and space station crews gather for the last time in orbit. The Atlantis astronauts leave behind a flag — and a challenge — for a U.S. commercial company to pick up. Credit: NASA)