The space shuttle and space station crews hugged goodbye on Sunday after more than a week together, but saved their most heartfelt farewell for Discovery.
On its final voyage after nearly three decades, Discovery, the most travelled rocketship ever, will be retired following this week's return to Earth.
The hatches between Discovery and the International Space Station were sealed on Sunday afternoon, setting the stage for the shuttle's departure first thing on Monday.
"We're going to miss you," the space station's commander, Scott Kelly, told the six shuttle astronauts. "But most of all we're going to miss Discovery.
"Discovery has been a great ship and has really supported the International Space Station more so, I think, than any other space shuttle. We wish her fair winds and following seas."
Shuttle skipper Steven Lindsey nodded in agreement, then shook hands with Kelly. Lindsey noted that all the mission objectives had been accomplished: The new storage unit carried up by Discovery was installed and unloaded, leaving behind an empty, pristine
compartment ready to serve its purpose.
Lead flight director Royce Renfrew radioed up congratulations to the two crews, before the hatches slammed shut. He said he was "really proud to take Discovery home at the very top of her game".
Mission Control gave Discovery's astronauts two extra days at the orbiting outpost. They took advantage of the bonus time to empty the storage unit of all the gear that went up inside it. The bonus days stretched the entire mission to 13 days on top of the
352 days already logged during Discovery's previous 38 missions.
In their last hour together, the 12 astronauts amused themselves in the new 6.4 metre-long, 4.5 metre-wide storage compartment. Taking turns a few at a time, they performed somersaults in the centre of the chamber, bounced off the walls, and floated through
with outstretched arms like underwater swimmers.
The astronauts were having so much fun that Mission Control was sorry to interrupt. "I hate to ring the recess bell on you," Mission Control radioed, reminding the shuttle crew of one last job remaining before the hatches needed to be shut.
Immediately after undocking, Discovery will fly a victory lap of sorts around the orbiting lab, essentially for picture-taking. Then the shuttle astronauts will pull out an inspection boom and survey
their ship for any signs of micrometeorite damage.
Landing is scheduled for Wednesday.
Aboard the space station, meanwhile, the crew hopes in the next week or two to unpack the humanoid robot that was left behind.
The robot, named R2 for Robonaut 2, is the first humanoid in space.
Mission Control, meanwhile, is monitoring a piece of space junk - an old rocket segment - that is threatening to come too close to the space station on Wednesday. Experts will assess the risk to the station following Discovery's undocking and determine whether the
complex will have to move out of the way. The shuttle is not expected to be affected by the debris, officials said.
Only two other shuttle missions remain.
Endeavour is due to blast off on April 19 with Kelly's identical twin brother Mark at the controls.
Atlantis will close out the 30-year shuttle program with a launch at the end of June.
