By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - Four veteran astronauts landed at the Kennedy Space Center in Florida on Monday to prepare for the launch of NASA's last space shuttle on a cargo run to the International Space Station.
Liftoff of Atlantis on the U.S. space agency's 135th and final shuttle flight is targeted for 11:26 a.m. EDT on Friday.
"It's such a pleasure to come down here when you have a rocket on the pad and it's got your stuff loaded on it," astronaut Rex Walheim told reporters shortly after arriving at the Florida spaceport.
Walheim and his crew mates -- commander Chris Ferguson, pilot Doug Hurley and astronaut Sandy Magnus -- had just nine months to prepare for their mission, which was added to buy time in case the companies NASA has hired to fly supplies to the station after the shuttle program ends encounter delays.
Space Exploration Technologies, known as SpaceX and owned by Internet entrepreneur Elon Musk, and aerospace company Orbital Sciences Corp hope to start flying freighters to the station next year.
NASA astronauts plan to hitch rides to the space station on Russian Soyuz space capsules, at a cost of more than $50 million a seat, until U.S. firms are ready to take on that business as well.
Atlantis carries a storage pod in its cargo bay filled with more than four tonnes of food, clothing, supplies and equipment for the space station, a $100 billion orbital complex the size of a five-bedroom house.
The station, which circles 220 miles above the Earth, is a partnership between the United States, Russia, Europe, Japan and Canada, built primarily by space shuttle crews over the past 11 years.
NASA points to the station as a fitting legacy to the shuttle program and wants to ensure it can remain continually staffed with a full crew of six.
So while trucking food and clothing is not the most glamorous job the shuttle has performed in its 30-year history, the program's final flight is critical for the station's long-term viability.
"When it's all over, we'll be very proud to put the right hand bookend on the space shuttle program," Ferguson said.
(Editing by Tom Brown and Todd Eastham)