CAPE CANAVERAL, Fla. – America’s manned space program roared back to life yesterday with the launch of Discovery, and engineers immediately began analyzing video of debris falling from the shuttle, hoping to rule out a problem like the one that doomed the last flight two and a half years ago.

National pride and the future of space exploration itself hung in the balance as Discovery and its crew of seven rose from the launchpad at 10:39 a.m. into a hazy blue sky, skirted two decks of clouds, and headed out over the ocean in the most scrutinized launch in NASA history and the first shuttle flight since the Columbia disaster.

NASA Administrator Michael Griffin urged everyone “to take note of what you saw here today: the power and the majesty of the launch, of course, but also the competence and the professionalism, the sheer gall, the pluckiness, the grittiness of this team that pulled this program out of the depths of despair two and a half years ago and made it fly.”

Nevertheless, Mr. Griffin and other NASA officials said they would not celebrate until Discovery comes home safely. Columbia, after all, seemed to be home free until it fell to pieces on its return to Earth.

Two chase planes and more than 100 cameras documented Discovery’s ascent from every possible angle to capture any sign of flying debris, and hours after the shuttle had settled into orbit, NASA officials said an object that may have been a 1 1/2 -inch piece of thermal tile appeared to break off from the Discovery’s belly during liftoff.

Also, a large object – perhaps a piece of foam insulation – seemed to fly off from the giant external fuel tank but did not hit the shuttle itself, NASA flight operations manager John Shannon said.

“The big question is, what is that?” Mr. Shannon said. He said it is too early to say whether the debris poses any danger to the shuttle. Mr. Shannon said the cameras have provided the space agency with more detailed images than it has ever seen before, and it not clear whether the debris is anything out of the ordinary.

Also, Mr. Shannon disclosed that the nose cone of the fuel tank hit a bird during a liftoff.

NASA promptly notified Discovery commander Eileen Collins of the debris and said the agency’s image-analysis experts were looking at the pictures frame by frame and would have more information this morning.

In addition, the astronauts will use a new 50-foot boom to inspect their ship today, and the crew of the international space station will photograph all sides of Discovery before tomorrow’s linkup between the two.

The baffling fuel gauge problem that thwarted a launch attempt two weeks ago did not recur this time, and the countdown was remarkably smooth. If the sensor had acted up during the countdown, NASA had been prepared to bend its safety rules to get the shuttle flying.

Space program employees and relatives of both the Discovery and Columbia crews looked on nervously as the shuttle lifted off.

“On behalf of the many millions of people who believe so deeply in what we do, good luck, Godspeed – and have a little fun up there,” launch director Mike Leinbach told Ms. Collins and her crew just before liftoff.

Across the country, Americans watched the liftoff, cheering and applauding in New York’s Times Square as the Discovery roared away from the launch pad. In the hometown of Japanese astronaut Soichi Noguchi, the pop of firecrackers and congratulatory cheers of “Banzai!” rang out.

At the Kennedy Space Center, nearly 2,500 guests of NASA, including first lady Laura Bush and brother-in-law Governor Bush, cheered, whistled, and clapped as the shuttle lifted off, watching through sunglasses as it soared out over the Atlantic. The spectators included members of Congress, as well as relatives of the 14 fallen Columbia and Challenger astronauts.

From Washington, the president wished the crew a safe and successful mission.

“Our space program is a source of great national pride,” he said in a statement, “and this flight is an essential step toward our goal of continuing to lead the world in space science, human spaceflight, and space exploration.”

Hours after Discovery had settled into orbit, Ms. Collins saluted “the great ship Columbia and her inspiring crew” and said of the fallen astronauts: “We miss them and we are continuing their mission. God bless them tonight and God bless their families.”

During the 12-day mission, Ms. Collins and her crew will deliver supplies to the space station and test new techniques for inspecting and patching the shuttle in orbit.

The 114th shuttle liftoff came after a humbling self-examination on NASA’s part, extensive safety modifications to the spacecraft, and many months of hurdles and setbacks.