NASA on Wednesday gave a green light for the return of Space Shuttle Atlantis to Earth on Thursday after determining the orbiter was undamaged by debris floating nearby.
"We are cleared for entry -- nothing was found missing or damaged on the thermal protection system, the heat shield of the Space Shuttle Atlantis or in fact any other part of the space shuttle, so we feel very confident we have a very good landing opportunity Thursday," shuttle program manager Wayne Hale said at a news conference.
"The weather forecast is excellent" for the shuttle and its six-member crew's scheduled 6:21 am (1021 GMT) landing at the Kennedy Space Centre in Cape Canaveral, Florida, he added.
In the event that becomes impossible, NASA would try for a landing Friday or decide to land the shuttle at the Edwards Air Force Base in California.
The six astronauts have enough oxygen, water and electricity to remain in orbit until Saturday.
Tuesday's discovery of a small, unidentified object orbiting along with Atlantis prompted the National Aeronautics and Space Administration to delay Wednesday's scheduled return by 24 hours to allow an inspection of the shuttle.
Poor weather conditions forecasted at the landing site also contributed to the postponement.
Hale said the mystery object was probably a piece of plastic used to adjust the thermal tiles during their installation on the orbiter's underbelly.
During nearly seven hours of inspections Wednesday to ensure the shuttle's heat shield is intact; the crew observed three additional objects floating near the orbiter. They also photographed a piece of debris floating near the shuttle's porthole that appeared to be a plastic bag.
Hale stressed that although Tuesday's mystery object had not been identified, "the nature of the debris has been overshadowed by the fact that we know the vehicle is in good shape, so it wasn't important."
The shuttle program manager said it was common to lose "little things", like a plastic bag or pieces of plastic, during shuttle missions.
Asked to identify the origin of the debris observed over the past two days, Hale said: "All those items come from the space shuttle."
The US space agency has strived to avoid damage to the orbiter's heat shield since a crack in the shuttle Columbia's protective skin caused it to disintegrate as it returned to Earth in February 2003, killing the seven astronauts on board.
Atlantis is capping a successful mission to install the International Space Station's first addition in nearly four years.
The Atlantis crew used the camera on the shuttle's robotic arm to scan the heat shield for potential damage before docking with the ISS last week and after leaving the orbiting laboratory this week.
The shuttle was determined free of damage following those safety checks, which were first used during two Discovery shuttle flights aimed at making flights safer, in July 2005 and July 2006.
Atlantis lifted off from Florida on September 9 on a mission to install two power-producing solar arrays on the space station, marking the first station-assembly work since the 2003 Columbia tragedy.
The solar arrays, unfurled last Thursday, measure 240 feet (73 meters) and will double the outpost's power capabilities. It took the station's robotic arm and three spacewalks to install the panels.
The last ISS construction work was in November 2002.
NASA plans 15 more flights to finish the project by 2010. At that time, the three remaining US shuttles are scheduled to be decommissioned.