Published: Mar 09, 2011 4:36 PM EST
Updated: Mar 09, 2011 1:36 PM EST

CAPE CANAVERAL, Fla.- Space shuttle Discovery aimed for an on-time touchdown Wednesday to wrap up a long flying career.

The world's most-traveled spaceship was due to return to Earth - for the last time ever - three minutes before noon.

"Right now, the weather looks great," Mission Control informed the six astronauts.

With just a few hours left to circle the world, commander Steven Lindsey wondered aloud whether Kennedy Space Center was the only landing site under consideration. Mission Control replied that it was, and that the backup landing strip in California had not been activated.

"I know you're from California," Mission Control told Lindsey. "Is there something you were thinking?"

"No, just curious," Lindsey replied. "No, we want to bring Discovery back to Florida."

Minutes later, the astronauts closed the payload bay doors in preparation for Discovery's final fiery ride through the atmosphere.

NASA's oldest shuttle has flown 39 missions over nearly 27 years. It's being retired after this voyage.

Discovery is headed back from the International Space Station. Its crew delivered and installed a new storage compartment, complete with a humanoid robot.

The mission added 13 days to Discovery's lifetime total of 365 days in space. Its total mileage is 148 million miles.

Once back at Kennedy Space Center, Discovery will be decommissioned over the next several months and sent to the Smithsonian Institution for display.

Endeavour and then Atlantis will fly once more each in the next few months. Then they, too, will be retired. Their final resting places have yet to be chosen. Endeavour - scheduled to blast off in less than six weeks - will be moved out to the launch pad Wednesday night.

NASA is under presidential direction to spread its wings beyond low-Earth orbit. The goal is to send astronauts to an asteroid and then Mars in the decades ahead. There is not enough money for NASA to achieve that and maintain the shuttle program at the same time. As a result, the shuttles will stop flying this summer after 30 years.

American astronauts will keep hitching rides to the space station on Russian Soyuz capsules, until private companies are able to provide taxi service to and from orbit. NASA expects to get another nine years out of the space station. --- Online: NASA: http://www.nasa.gov/mission(underscore)pages/shuttle/news/index.html

(Copyright 2011 by The Associated Press. All Rights Reserved.)