Discovery glided down through an overcast sky onto the Kennedy Space Center runway at 9:14 a.m., allowing NASA to declare total victory for the first time since before the 2003 Columbia disaster.
It was so cloudy, shuttle commander Steven Lindsey couldn't spot the runway until about a minute before landing.
"Welcome back Discovery and congratulations on a great mission," Mission Control told Lindsey after Discovery rolled to a stop.
Later, Lindsey noted that he and his crew accomplished both major objectives: completing the post-Columbia testing of the shuttle and its redesigned fuel tank, and readying NASA to resume building the international space station.
"We're ready to go assemble station," Lindsey said after climbing out of Discovery, "and we're ready to start flying shuttles on a more regular basis."
The smooth landing left NASA officials jubilant, after conquering the chronic threat of foam chunks that break off the external fuel tank during launch still a problem, but not a serious one in this mission.
"This is as good a mission as we've ever flown," NASA Administrator Michael Griffin said. "But we're not going to get overconfident."
The shuttle came in from the south, swooping over the Pacific, Yucatan Peninsula, Gulf of Mexico and across Florida to cap a 5.3 million-mile journey that began on the Fourth of July.
A last-minute buildup of clouds prompted NASA to switch the shuttle's direction for landing. By the time Discovery approached, it was so cloudy, Lindsey couldn't spot the runway until about a minute before landing.
A couple of minutes out, NASA made a racket to keep birds out of the way of the approaching spacecraft. Car horns blared, and the sound of gunshots and firecrackers erupted.
At touchdown, shouts and whistles came from the few hundred astronauts' relatives and space center workers at the runway. "It's exciting to see the shuttle back," said astronaut Scott Kelly, the identical twin brother of Discovery's co-pilot, Mark Kelly. "We're back on track with maybe flying the shuttle regularly here starting again in August."
Atlantis is up next with a crew poised to carry out assembly of the international space station, a task put on the back burner after Columbia.
Congratulations poured in from afar. "A proud nation congratulates the brave shuttle Discovery crew on the completion of their successful return to flight mission," said Sen. Kay Bailey Hutchison, R-Texas.
The buildup of clouds shortly afterward prompted NASA to switch the shuttle's landing direction, CBS News correspondent Bob Orr reports. Officials at Marine Corps Air Station Cherry Point in eastern North Carolina also said they had been alerted for emergency landing duty as a precaution.
The shuttle, with commander Steven Lindsey and co-pilot Mark Kelly at the controls, plunged out of orbit an hour before touchdown Monday morning with the firing of the braking rockets, and began the hour-long descent. The flight path had the spacecraft coming in from the south, swooping over the Pacific, Yucatan Peninsula, Gulf of Mexico and across Florida to cap a 5.3 million-mile journey that began on the Fourth of July.
"It was beautiful," Lindsey told controllers. "We could see the bright orange glow above and I could see the Earth moving below and it was just spectacular. We actually also saw the moon through the plasma (scorching gases), so it was a great entry and a great landing."
NASA was certain that Discovery's heat shield was intact and capable of protecting the spaceship during the fiery re-entry. The shuttle itself was cleared Sunday for landing. CBS News correspondent Teri Okita reports the shuttle crew spent Sunday doing final top-to-bottom checks of the spacecraft. They also tested a leaking unit that powers hydraulics used for steering and braking.
Repeated inspections of the ship's thermal skin in orbit had given NASA confidence. Unlike on Discovery's flight a year ago, the external fuel tank shed little foam during liftoff. That flight was the shuttle's first after the Columbia disaster, when a chunk of falling hard foam doomed the shuttle in 2003.
Officials acknowledged re-entry was, along with the launch, the most dangerous phase of the mission and nothing could be taken for granted until Discovery was safely back home following its trip to the international space station. Toward that end, Discovery's astronauts and flight controllers kept close watch on a slightly leaking power unit that tested out fine a day earlier in orbit.
NASA did not know whether harmless nitrogen gas or flammable hydrazine was dripping from the auxiliary power unit, one of three needed to drive the hydraulic landing systems. The leak was small, managers said. If it worsened during re-entry, considered unlikely, the unit would shut down automatically and Discovery would become the first shuttle to land with only two functioning auxiliary power units.
Discovery sported a new, tougher type of landing gear tire for improving safety. In another shuttle first, a GPS receiver was on board to help guide Discovery down to the 3-mile-long landing strip.
It was the first shuttle landing at Kennedy in nearly four years. Columbia never made it back in February 2003, it shattered over Texas, and Discovery had to take a weather detour to California last summer.
Some at NASA, including the chief engineer and NASA's top safety officer, wanted to put off the latest mission until further repairs could be made to a particularly vulnerable area of the fuel tank. But NASA Administrator Michael Griffin opted to press ahead with what turned out to be the space agency's first Independence Day launch.
The shuttle carried up seven astronauts, but departed the space station on Saturday with six: Lindsey, Kelly, Michael Fossum, Piers Sellers, Lisa Nowak and Stephanie Wilson. German astronaut Thomas Reiter was left behind for a half-year stay, joining two other men there and boosting the station's crew size to three.
The Discovery crew conducted three spacewalks, one of them to test shuttle patching techniques, and used a 100-foot inspection crane to check the shuttle's entire thermal armor for any damage from launch or orbital debris. The rocketship turned out to be the cleanest seen in orbit from a thermal perspective, officials said.
The astronauts also demonstrated that the boom could function as a work platform for spacewalkers and delivered several thousand pounds of supplies to the space station, still in need of restocking because of the 2 1/2-year grounding of the shuttle fleet after Columbia's demise.
By fixing a broken rail car on the outside of the space station, the astronauts paved the way for space station construction to resume in earnest with the next shuttle flight.
Atlantis is scheduled to blast off as early as Aug. 27. Unlike Discovery's missions, which focused primarily on the flight test aspects, the Atlantis crew will haul up a major space station piece, a building-block beam, and attach it to the orbiting outpost.
The station is just half finished, eight years after the first piece went up. NASA wants it completed by the time the three remaining shuttles are retired in 2010, as per President Bush's mandate, to make way for a new spaceship capable of carrying astronauts to the moon.