When astronauts aboard the space shuttle Atlantis got their musical "wakeup call" from earth on Saturday, the audio blended haunting instrumentals with a not-so-subtle message: An era of American space travel is ending.

The song was Coldplay's "Viva La Vida," which leads off with the line "I used to rule the world."

To NASA workers and to shuttle fans alike, the song served as a wistful tribute to a vehicle that for three decades has been the leading symbol of America's space program. The current mission, by the Atlantis orbiter, is the final one.

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Since the first launch in 1981, the orbiters may not have literally ruled the world, but they did soar above it. They helped to maintain US leadership in space exploration, even as they also built bridges beyond US borders by serving the International Space Station.

As the song faded out, Atlantis pilot Doug Hurley responded, "Thanks for that great message and awesome ride to orbit, and the 134 before that with this tremendous space shuttle program."

In a video on the NASA website, the wakeup music is followed by a mass greeting from employees of NASA's Marshall Space Flight Center in Huntsville, Ala., in charge of shuttle propulsion systems.

It's hard to read too much into the song lyrics when applied to NASA, especially when there's not even consensus about what the song means back on earth. But here are some of the words, along with some space shuttle details:

I used to rule the world

Seas would rise when I gave the word

Now in the morning I sleep alone

Sweep the streets I used to own

The shuttle has been called the most complex machine ever built. "Its main engines stretched design and metallurgical capabilities," NASA says. And its thermal protection system, shielding the orbiter from temperatures as high as 3,000 degrees F. during re-entry, "was a work in progress until shortly before the first shuttle launch."

Though the current mission is the 135th and final one for the shuttle program, NASA won't be left to just sweep streets or close its doors. Thousands of shuttle-related workers will lose their jobs, but the space agency will continue to work on manned and unmanned space exploration.

NASA may turn to commercial launch systems to service low-orbit needs like the space station, while its own engineers focus on bringing humans to an asteroid or to Mars.

I used to roll the dice

Feel the fear in my enemy's eyes

Listen as the crowd would sing:

"Now the old king is dead!

Long live the king!"

The space shuttle was conceived even as the Apollo program was busy finishing its ambitious race to land the first man on the moon. In September 1969, a task force appointed by President Nixon recommended, among other things, “low-cost, flexible, long-lived, highly reusable, operational space systems with a high degree of commonality and reusability.”

One minute I held the key

Next the walls were closed on me

And I discovered that my castles stand

Upon pillars of salt and pillars of sand

Space travel is unforgiving of mistakes or defects, and is made possible only by the willingness of Congress and others to fund it. On Saturday the big task for the Atlantis crew of four astronauts was to check the space shuttle's delicate heat shield for any damage from Friday's launch.

On Sunday, Atlantis plans to dock with the International Space Station to deliver more than four tons of supplies. After that, the future for NASA's orbiters is as museum pieces in cities like New York and Washington.

The Saturday wakeup call is just one musical tribute to the shuttle program. A more formal one was a "Fanfare for STS-135," composed specially for this final mission by Bear McCreary. "There is both celebration and reflection at hand," the composer says on his website. "I wanted to capture this dichotomy with my fanfare."

The piece was played Friday at a launch "TweetUp" event.

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Material from the Associated Press was used in this story.