(CNN) -- Some 220 miles above the Earth's surface, the shuttle Discovery docked Saturday afternoon with the International Space Station for the last time.
Due to problems lining up with each other, the shuttle's "hard-mating" with the permanent orbiter threatened to push the six-man crew off schedule. The hook-up was finished around 3 p.m., yet NASA's Mission Control noted a possibility that the installation of an express logistics carrier would not be completed until Sunday, one day later than planned.
Instead, the crew took a little longer to tackle the job -- getting permission from the space agency's mission control to sleep in an extra 30 minutes in return for the long day's work, according to NASA's Twitter feed.
Having been removed from the shuttle's cargo bay and attached to the station's truss, or backbone, the 8,235-pound logistics carrier will be used to stow spare parts, including an extra radiator that was brought up by Discovery's crew.
Overall, there were no major problems on the third day of the shuttle's 11-day mission, during which the crew is set to deliver a storage module, a science rig and spare parts to the space station and its six occupants.
Hatches to and from the shuttle and space station opened at 4:16 p.m. Saturday, followed by a brief welcome ceremony and safety briefing.
Discovery started its 39th and final flight with a launch late Thursday afternoon from Kennedy Space Center in Florida.
Originally scheduled for November, the shuttle's launch had been delayed to make repairs to the external tank's support beams.
And NASA halted its countdown on Thursday, at five minutes, because of a computer problem related to safety on the "eastern range." But after a confirmation that all was good to go, the countdown resumed, and the shuttle lifted off about three minutes behind its planned 4:50 p.m. ET launch.
At least four pieces of foam were seen flying off Discovery about four minutes into the launch. NASA officials said they didn't foresee a problem -- explaining that, at that altitude, the flying foam was unlikely to do any damage to the spacecraft.
That said, on Saturday two astronauts shot numerous pictures of the shuttle's thermal protection system, which will be sent down for analysis to make sure there is no significant damage.
Astronauts on Sunday will continue moving items brought up on Discovery over to the space station. Final preparations will also be made for a spacewalk Monday, when astronauts Alvin Drew and Steve Bowen will install a power extension cable, move a failed ammonia pump and perform other operations outside the shuttle.
On day six of the mission, astronauts will work to attach a permanent module -- known as Leonardo -- to the station. The module will be home for experiments in fluid physics, materials science, biology, biotechnology and other subjects.
The Discovery crew is headed by Steve Lindsey. Bowen, a late addition, became the first ever astronaut to fly consecutive missions after he was assigned to take the place of Tim Kopra when Kopra was injured last month in a bicycle accident, according to NASA.
Prior to Thursday's launch, Discovery had spent 352 days in orbit, circling the Earth 5,628 times. It has also carried 246 crew members, more than any space vehicle in history.
"In a way, it's ... sad to see the last flight," astronaut Steven Swanson said Thursday. "It's such a wonderful vehicle."
The last scheduled launch of Space Shuttle Endeavour is set for April 19. It will be commanded by Mark Kelly, the husband of U.S. Representative Gabrielle Giffords, who is recovering from being shot last month in Tucson, Arizona. The last ever shuttle mission will be Atlantis, tentatively scheduled to launch during the summer.
Discovery was the first space shuttle to dock with a space station of any kind when it met up on June 4, 1998, with Russia's now defunct Mir space station. The craft also was the first to hook up with the International Space Station, doing so on May 29, 1999, according to NASA. Saturday's event marked the 13th such docking for the Discovery.