This story was updated at 1:50 p.m. EDT.

CAPE CANAVERAL, Fla.  - The space shuttle Discovery roared into space Tuesday, piercing a Florida morning sky today and launching seven astronauts on NASA's first orbiter mission since the Columbia disaster.

After almost two weeks of delay, two and a half years without a shuttle flight and $1.4 billion in return-to-flight work, Discovery successfully left Earth behind on a 12-day test flight to the International Space Station (ISS) with no hint of the fuel sensor glitch that scrubbed a July 13 launch attempt. Typical Florida weather, including rain storms and a potential launch threat from electrified anvil clouds, was not an issue here at NASA's Kennedy Space Center (KSC) spaceport.

"With an early morning launch, we hope we give you a good show," Discovery's STS-114 commander Eileen Collins told reporters before the flight. "We're very prepared."

Discovery launched right on time at 10:39:00 a.m. EDT (1439 GMT), rising above Launch Pad 39B here at KSC. Eight minutes and 29 seconds later, Collins and her crew reached orbit.

"Okay Eileen our wait may be over," said NASA launch director Michael Leinbach just before liftoff. "Have a little fun up there."

In addition to Collins, pilot James Kelly, flight engineer Stephen Robinson and mission specialists Andrew Thomas, Wendy Lawrence, Charles Camarda and Soichi Noguchi - of the Japanese Aerospace and Exploration Agency (JAXA) - rode Discovery into space.

"That hits you hard," said NASA astronaut David Wolf, of Discovery's successful liftoff. "I'm all choked up."

Video showed what might have been at least two light-colored objects flying off Discovery as the shuttle cleared the launch pad, and what appeared to be a large piece of debris coming off the external fuel tank two minutes into the flight.

Deputy shuttle program manager Wayne Hale raised the possibility that the light-colored objects were harmless pieces of paper that protect Discovery's thrusters before launch. But he insisted it was too soon to say what the cameras may have picked up, and he gave assurances the multitude of images will be examined frame by frame in the coming hours and days.

"No telling what might be there or what's not there -- we hope nothing," he said.

Today's space shot came 13 days after NASA's first attempt to launch Discovery on July 13, which flight controllers scrubbed just as Collins and her astronaut crew were strapping into their seats. A problematic fuel sensor reading during a standard countdown check forced the scrub, prompting an exhaustive engineering investigation that was ultimately unable to determine the glitch's exact cause.

Collins and the STS-114 crew followed the investigation during the two-week launch delay, breaking quarantine only once during that time to visit family and friends. Then it was back to training and, ultimately, launch.

"We can still see the external tank out the window...it looks beautiful and the sun's going down about now," Collins said about 26 minutes after external tank separation. "It looks beautiful and the sun's going down."

During their mission, the STS-114 astronauts will test out a suite of new tools and methods of on-orbit inspection and repair of their spacecraft. They will also deliver a vital cargo shipment to the ISS, including a spare gyroscope that Noguchi and Robinson will install during their second of three planned spacewalks.

"This flight is important for NASA...it's the first step in getting back to flying the shuttle and building the International Space Station," NASA astronaut Nicholas Patrick told SPACE.com. "But for me personally, it's very important because I'm looking forward to flying aboard the orbiter in April [2006]."

Patrick is assigned to the crew of Discovery's STS-116 flight, where he will be in charge with directing the robotic arm and the added 50-foot (15-meter) orbital inspection boom that the STS-114 mission will test out. Today's spaceflight is also geared at testing potential repair techniques for shuttle tiles and heat-resistant panels, and resupplying the ISS.

The space station was flying above the southern Indian Ocean, just west of Australia, during Discovery's launch. Its Expedition 11 crew - commanded by cosmonaut Sergei Krikalev with NASA astronaut John Phillips serving as flight engineer - watched the launch via a video link between the orbital facility and its NASA mission control in at Johnson Space Center (JSC) in Houston, Texas.

JSC spokesperson James Hartsfield said the ISS crew sent their congratulations down to flight controllers on the successful shuttle space shot.

Discovery's STS-114 crew will now spend the next two days chasing the ISS, and are expected to dock at the station at 7:18 a.m. EDT (1118 GMT) on July 28.

Today's liftoff was NASA's 114^th shuttle flight and the 31^st launch for Discovery. The launch also marks the 17^th U.S. spaceflight to the ISS.

"It's exciting...a gee whiz moment," astronaut Jim Reilly, a mission specialist assigned to NASA's STS-117 mission, told SPACE.com just before the launch.

Unexplainable glitch?

Discovery's liftoff came after an extensive investigation by shuttle engineers to track down an anomaly that led one of four liquid hydrogen fuel guage to fail a preflight test during the orbiter's July 13 launch attempt.

Known as engine cut-off (ECO) sensors, the gauges measure liquid hydrogen levels inside Discovery's external tank. Four similar sensors inside perform the same function inside Discovery's liquid oxygen feed line. All eight of the sensors are designed to shut down Discovery's three main engines before the external tank runs out of fuel.

The faulty sensor read 'wet' - indicating a full external tank - during a test in which launch controllers force the sensors to read 'dry' - indicating an empty tank. One sensor continued to read 'wet' in the test, prompting the scrub. The glitch was similar to sensor problem experienced during an April tanking test with a different external tank, though a second check of that fuel tank turned up nothing suspect, NASA officials said.

"We may not ever be able to determine any exact single failure for this problem," NASA test director Pete Nickolenko said before the flight.

After the April test, engineers replaced wiring and other hardware associated with the sensor system. They also switched Discovery to a new launch stack in order to use a new external tank equipped with an additional heater to prevent ice formation.

The investigation following the July 13 launch scrub found some hitches with electrical grounding, which engineers resolved, as well as the potential of electromagnetic interference from other external tank and orbiter hardware. Additional sensor tests were instituted during Discovery's launch countdown to verify the ECO sensors were working properly.

"You go through so many trials and tribulations, to go through that troubleshooting from these past couple of weeks [makes] it more special," Discovery's vehicle manger Stephanie Stilson told SPACE.com before the launch.

Returning to space

Discovery's STS-114 flight is NASA's first shuttle launch since 2003 accident that claimed the lives of seven astronauts and destroyed the space shuttle Columbia during the STS-107 mission.

"We've been interested in making sure this mission is as successful as it can be," Collins said. "Not only that, but making sure that we do the right thing not only just for STS-114 but for every mission that's going to follow us."

Columbia was destroyed on Feb. 1, 2003, as it reentered the Earth's atmosphere after a successful science mission that began 16 days earlier. But launch debris from Columbia's external tank separated at launch and struck Columbia's left wing leading edge, fatally crippling the spacecraft's vital heat-resistant skin. During reentry, hot gases entered the hole from that collision and led to the orbiter's destruction.

"As difficult as the [Columbia] accident was, I think the accident has given all of us a sense purpose and that helps us all in dealing with the loss," Patrick said. "Instead of shutting down the space program, which might have happened, we've taken the lessons learned from Columbia and applied them to the shuttle as well as the next vehicle."

Family members of Columbia's lost crew issued a statement before Discovery's initial launch attempt and praised the efforts of accident investigators, NASA and the independent oversight panel that watched over the agency's return to flight work.

"We hope we have learned and will continue to learn from each of these accidents so that we will be as safe as we can be in this high-risk endeavor,'' the statement read. "Godspeed, Discovery."

Today all eyes and more than 100 cameras - ranging from high-power imagers on the ground to aircraft-mounted systems - will be on Discovery's ascent, watching closely for any signs of ice of foam debris from the shuttle's external tank.

A camera mounted on Discovery's external tank gave flight controllers a spotless view of the moment of separation, when Discovery cast off the fuel tank and headed on its way.

Bob Page, head of NASA's intercenter photo working group, said imaging officials should receive the first high-definition television images of Discovery's launch about 15 minutes after liftoff. Additional telescope, radar and high-resolution data will be processed as it comes in throughout the day. Video from Discovery's solid rocket boosters and shuttle-mounted systems will be relayed to the working group in the next two to three days, he added.

NASA officials hope that a photography experiment - which put visible and infrared telescopes in the turret nose of a high-altitude aircraft - will provide high-resolution images up through main engine cutoff.

NASA has spent the last two years working to meet 15 return to flight recommendations from Columbia accident investigators, who believed should be addressed before today's launch. The Stafford Covey Return to Flight Task Group - an independent group that watched over NASA's work - passed the agency on only 12 of those items, but said NASA had met partial requirements of the remaining three.

"I believe there is a resolve now at NASA that is similar to the resolve that existed just after the Apollo 1 fire," former NASA flight director Gene Kranz told SPACE.com, before the launch. "And that resolve, I believe, will prevent another accident like Columbia."

Busy first day

Discovery's crew has had a busy day, with more work in space ahead of them.

They awoke this morning at 12:30 a.m. EDT (0430 GMT) and together and took a crew photo before donning their orange flight suits and walking out of the astronaut crew quarters here to cheers and applause. Most of the crew had a light breakfast before today's space shot, with Collins choosing whole wheat toast and fruit while Kelly opted for mixed fruit alone. The STS-114 spacewalkers, Noguchi and Robinson, each chose fruit and a meat sandwich. Noguchi settled for steak, while Robinson chose chicken and later strummed on his guitar.

"Steve is quite the musician," said shuttle pilot Alan Poindexter, currently assigned to NASA's STS-120 mission. "He's quite the accomplished guitarist."

The astronauts will conduct a photo survey of their external tank - a typical post-launch task - much earlier and closer to the tank than on past flights to get an up-close look at how its insulation foam weathered the space shot. The survey is also designed to verify how modifications to the tank, such as the removal of foam along a bipod fitting that connects to the shuttle, performed during launch.

Before entering the orbiter, some STS-114 crewmembers took time to send messages home to their loved ones.

Camarda displayed a sign emblazoned with 'Hi Dad!' and others with more messages to his family. Kelly embraced members of the seven-person close out crew assisting the STS-114 astronauts before boarding Discovery. Soichi proudly waved a sign that read 'Out to Launch' as well as a JAXA flag commemorating the 50^th anniversary of the agency's launch vehicle development. The pad close out crew shut Discovery's hatch at about 9:00 a.m. EDT (1300 GMT).

The astronauts conducted a photo survey of their external tank - a typical post-launch task - much earlier and closer to the tank than on past flights to get an intimate look at how its insulation foam weathered the space shot. The survey, which brought the orbiter within 1,500 feet of the tank, is also designed to verify how modifications to the tank - such as the removal of foam along a bipod fitting that connects to the shuttle - performed during launch.

Thomas took digital still images of the tank while Noguchi recorded it with a video camera about three minutes after the shuttle reached orbit, though the images will not be relayed to the ground until later in the mission, NASA officials said.

Later, the crew will perform initial checks of Discovery's robotic arm, a task typically reserved for Flight Day 2, and also take images to make sure that the orbital boom and the shuttle's antenna survived the launch unscathed, NASA officials said.

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They are expected to return to Earth here at NASA's KSC Shuttle Landing Facility on Aug. 7 at 5:46 a.m. (0946 GMT).

"Flying in space shows one of the great aspects of the human spirit and we are really honored to be a part of it," Robinson said.

The Associated Press contributed to this report.