There were hugs and handshakes as Discovery's astronauts said their goodbyes to the astronaut and cosmonaut who live aboard the international space station. The crews then closed the hatches between the ship and orbiting lab.
CBS News Correspondent Lee Cowan reports that, with future flights grounded indefinitely, it could be a while before the space station gets another visit — and the clock is ticking.
The station itself is only half finished, and there are promises that have to be kept to the agency's international partners before the shuttle are retired five years from now.
Astronaut Scott Parazynski — who is scheduled to install a new truss on the space station next year — told Cowan that the project is crucial to NASA's larger mission.
"We're also going to be using the laboratory of the space station to develop the technologies that will take us back to the moon, not just to visit, but to stay," Parazynski said.
Before the spacecraft left for good, Discovery's astronauts planned to fly a farewell loop around the station, then fire the shuttle's jets to reposition the spacecraft and prepare for the voyage home.
Discovery's astronauts are scheduled to complete their 13-day mission Monday when the first shuttle to return to space since the 2003 Columbia tragedy is set to land in Florida.
"We are so happy to have spent the time up here," Discovery's commander Eileen Collins told the station's two crew members, who have been there since April. "These are memories that we will have forever."
Discovery's seven astronauts spent a day longer than originally planned aboard the station to bring over additional supplies, such as paper, laptop computers and surplus food and batteries. Discovery is the first shuttle to visit the station since 2002.
Meanwhile, a former astronaut spoke highly of the Discovery crew, while criticizing the U.S. space program. CBS News Correspondent Larry Miller reports that Apollo astronaut Buzz Aldrin says the Discovery shuttle crew knows its craft inside and out and he does not think they will be nervous on the return journey to earth.
Miller adds that in a recent interview with the BBC, Aldrin was critical of the shuttle program. He said it's now time to change the way people travel into space. The second man to walk on the moon refused to say whether this should be the last shuttle mission, but said it's time for the United States to make a hard decision on how to go forward.
NASA is investigating whether repairs to a small crack in the foam on Discovery's fuel tank may have caused a 1-pound section of the insulation to break off during liftoff, officials said late Friday.
The shallow crack, just six-tenths of an inch long and two-tenths of an inch wide, was sanded away at the Louisiana manufacturing plant before the tank was shipped to Cape Canaveral, Fla. No new foam was applied to the spot.
It's a common repair procedure, NASA officials said.
What's intriguing, officials said, is that the repair was made to the approximate area where the big chunk of foam came loose during Discovery's launch on July 26. They cautioned, however, that there is no evidence yet that the repair contributed to the foam loss.
The external fuel tank was redesigned following the 2003 Columbia tragedy, but no improvements were made to the area where the foam came loose. Lockheed Martin Corp. built the tank at its Michoud Assembly Facility in New Orleans.