We're the only craft capable of bringing significant cargo back from the space station.
The five Atlantis astronauts are the space station's first visitors in more than two months.
That set the stage for the spacewalk involving three of the space station's six-man crew.
Both Marshburn and Hadfield are scheduled to leave the space station at 7:08 p.m.
The ammonia coursing through the plumbing is used to cool the space station's electronic equipment.
He acknowledged that leaving the space station without any crew members increased the risk for trouble.
"We're going to do what's safest for the crew and for the space station, " Suffredini said.
The cargo capsule will continue its orbit Wednesday as it travels toward the space station.
This marks the first successful cargo mission to the space station by a private company.
FORBES: SpaceX Dragon Successfully Berths With Space Station
The population on board the space station is to grow to six next spring.
Since Expedition 1 in 2000, the space station has been visited by 204 astronauts.
BBC: Nasa back in contact with the International Space Station
The ship was carrying food, supplies, fuel and other equipment for the space station.
FORBES: Progress 46 Successfully Docks With International Space Station
Challenges of physically connecting Dragon with the space station are the toughest elements of the mission.
The crew of the space station is expected to rise from three to six in mid-2009.
BBC: NEWS | Science/Nature | Endeavour launched from Florida
For similar reasons the report tells NASA to extend the life of the space station.
The 'Endeavour' is tentatively scheduled to rendezvous with the Space Station on December 6.
To conduct the test, the Progress 47 initially undocked from the space station on July 22.
MSN: Unmanned Russian cargo ship says goodbye to space station
After adjustments were made, the spacecraft successfully redocked to the space station on Saturday.
MSN: Unmanned Russian cargo ship says goodbye to space station
The space station normally leaks anyway, NASA official Michael Suffredini told reporters on Friday.
Several visiting unmanned spacecraft are expected to deliver supplies to the space station during Expedition 32.
MSN: Space station crew launches into orbit on Russian craft
Getting people on and off the space station is not, actually, rocket science any more.
The Russians also are preparing to launch a Progress supply ship to the space station on Tuesday.
The debris was predicted to pass about 23 kilometers (14.2 miles) from the space station, NASA said.
But this go around, the Soyuz only orbited four times before hooking up with the space station.
Little Kirobo is pencilled in to enjoy a spell on the space station sometime after summer 2013.
ENGADGET: Alt-week 3.9.13: Sunstones, knotted vortices and a zero-g robot
Mr Shkaplerov, Mr Ivanishin and Mr Burbank are due to remain at the space station until March.
Any of these problems can be dangerous in the close, confined, pressurized quarters of the space station.
But Cmdr Hadfield insisted his social media activities were secondary to his main functions at the space station.
There were even some suggestions of abandoning the space station entirely due to concerns about the failed launch.
Astronauts released the unmanned SpaceX capsule, named Dragon, from the end of the space station's giant robot arm.
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