HOUSTON (AP) – The shuttle Discovery backed away from the international space station and started a two-day journey home after its crew bade farewell to the residents of the orbiting outpost and left behind U.S. astronaut Suni Williams for a six-month stay.

Discovery is scheduled to return to Earth on Friday after a 13-day flight.

Under the control of pilot William Oefelein, the shuttle pulled about 450 feet back from the space lab before its jets were fired. Discovery will stay about 46 miles from the station for an inspection of its heat shield Wednesday, allowing the astronauts to return to the space lab in case damage is found.

“Discovery departing,” said American space station commander Michael Lopez-Alegria after the traditional ringing of a bell at the station.

Although they didn’t expect a problem, flight controllers were keeping an eye on two items lost during the mission’s four spacewalks that are now space junk – a 7-inch-long socket and a camera – because of the small chance they could hit the shuttle.

During eight days at the space station, Discovery’s astronauts made four spacewalks, during which they rewired the station’s power system, installed a 2-ton addition; and coaxed a stubborn solar panel to fold up accordion-style into its box.

“It’s always a goal to try and leave some place in a better shape than it was when you came,” said Discovery commander Mark Polanksy. “And I think we’ve accomplished that.”

The fourth spacewalk – to fix the jammed solar panel – was added at the last moment. That extended the mission by one day and put astronaut Robert Curbeam in the history books, with a record four spacewalks in a single shuttle mission.

Williams, who arrived aboard Discovery, becomes the newest member of the three-person space station crew. Discovery is bringing home her predecessor, German astronaut Thomas Reiter, who spent six months in orbit.

During the farewell ceremony before the two crews parted, Williams playfully nudged Reiter into the shuttle using her floating foot.

Lopez-Alegria saluted the departing Reiter for his “competence, conscientiousness and consistency” and pronounced him a “model astronaut.”

“By the authority vested in me, which I just invented, we would like to make you an honorary member of the NASA astronaut corps,” Lopez-Alegria said, pinning wings onto Reiter’s polo shirt.

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