"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.
"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.
In the event that becomes impossible, NASA will try for a landing on Friday or may 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.
The discovery of a small, unidentified object orbiting along with Atlantis prompted NASA to delay yesterday'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.
Mr 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.
Lengthy inspection
During nearly seven hours of inspections to ensure the shuttle's heat shield was 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.
Mr Hale stressed that although the 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.
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, a huge solar array, in nearly four years.
NASA plans 15 more flights to finish the project by 2010 when the three remaining US shuttles are scheduled to be decommissioned.