It lifted off from its launching pad in a thunderous blast of smoke and fire and arced through partly cloudy Florida skies, leaving a huge trail of condensation.

Minutes before liftoff, ground control wished Commander Eileen Collins and the crew a safe mission. "It's time for us to return to flight. Godspeed and we will see you in a couple of weeks," said orbiter test director Mark Taffet.

Discovery reached orbit eight minutes and 40 seconds after the lift off from the Kennedy Space Center in Florida.

Two minutes after launch, Discovery's two solid fuel rocket boosters separated from the main orbiter, which then jettisoned its external fuel tank once in orbit in a picture-perfect start to the mission.

NASA managers heaved a sigh of relief at the successful launch that marks the first manned US space flight since the shuttle fleet was grounded after the Columbia disaster on February 1, 2003. A scheduled launch on July 13 was scrubbed because of a faulty fuel level sensor.

First Lady Laura Bush and Florida Governor Jeb Bush, a brother of the US president, were at the Kennedy Space Center to witness the start of the historic "return to flight" mission.

Experts closely monitored the spacecraft's first two minutes of ascent, captured by more than 100 cameras on the ground and aboard two airplanes.

They focused particularly on the external tank's insulation that has been improved since Columbia burst into flames, killing all seven astronauts aboard.

The 2003 disaster was blamed on a piece of foam that detached itself from the tank upon liftoff, causing a gash that allowed superheated gases to penetrate the orbiter when it reentered the Earth's atmosphere.

During the 12-day mission, the crew will test safety measures adopted after the Columbia disaster.

Once Discovery reached orbit, Collins tipped the shuttle slightly so the crew could see the external tank as it was jettisoned.

The unprecedented maneuver aimed at determining whether any insulating material fell off the massive tank at launch as was the case with Columbia.

The crew will perform several more high-risk operations during the mission, which is partly designed to test new safety procedures.

As Discovery approaches the International Space Shuttle on Thursday, Collins will flip the orbiter over, so the ISS crew can take photographs to help determine whether the shuttle's thermal protection system suffered any damage during liftoff.

During the operation, Collins will briefly lose visual contact with the ISS, in a departure from NASA regulations for a docking approach.

In another risky maneuver, a laser mounted on boom will move alongside the orbiter to inspect it for damage. Any contact with the shuttle's surface could have disastrous consequences.

During one of three planned spacewalks on the Discovery, Japanese mission specialist Soichi Noguchi and his US counterpart Stephen Robinson will test repair techniques adopted after the Columbia disaster.

They will test the use of toxic chemicals to repair the shuttle, but are ready to abort the walk if the materials turn out to be too dangerous to handle in space.

The crew will also deliver supplies and equipment to the International Space Station (ISS).

earlier related report
Discovery set for launch as weather conditions improve The Discovery crew took position aboard the orbiter under clear Florida skies Tuesday, about two hours before the planned liftoff of the first space shuttle mission since the 2003 Columbia disaster.

NASA teams closed the hatch of the spacecraft after the seven astronauts strapped into their seats in readiness for a 10:39 am (1439 GMT) launch from the Kennedy Space Center (KSC.)

As bright sunshine illuminated clear skies over the Florida seashore launch pad, NASA managers were increasingly confident the weather would cooperate.

"Conditions are excellent here at KSC," said NASA spokesman George Diller.

The crew members also appeared upbeat, smiling and waving as they boarded the shuttle, clad in their distinctive orange suits.

Japanese mission specialist Soichi Noguchi grinned as he held up a handwritten sign saying: "out to launch."

Experts said there was only a 20 percent probability bad weather would prevent a liftoff, after earlier forecasts put the likelihood at 40 percent.

NASA managers were also hopeful a fuel gauge that malfunctioned previously would work properly this time around.

"The countdown activities are very routine, it's very smooth," said Diller.

As the shuttle's huge external tank was being filled during the night, engineers kept a close eye on the fuel sensor that caused a last-minute cancellation of a planned launch on July 13.

Tests indicated the sensor was working normally, but NASA managers have said that even if it fails they would still go ahead with the launch, provided they understand the cause of the glitch.

The sensor is one of four that monitor hydrogen levels in the tank to prevent a premature shut off of the shuttle's three engines.

During the 12-day mission, the crew will deliver supplies and equipment to the International Space Station (ISS) and will test safety measures adopted after Columbia burst into flames upon re-entering the Earth's atmosphere on February 1, 2003, killing all seven astronauts.

The tragedy was blamed on a small piece of insulation that broke off right after liftoff and struck the orbiter's left wing, causing a crack that allowed superheated gases to penetrate the structure just minutes before the planned landing.

Once Discovery reaches orbit eight minutes after liftoff, Commander Eileen Collins was scheduled to slightly tip the orbiter so the crew can see the external tank as it is jettisoned, to determine whether any insulating material fell off.

Collins will also flip the orbiter over as it nears the ISS Thursday, so the astronauts aboard the space station can inspect the shuttle's thermal protection system.

During one of three planned spacewalks on the Discovery, Noguchi and his US counterpart Stephen Robinson will test repair techniques adopted after the Columbia disaster.

Several dignitaries, including First Lady Laura Bush and Florida Governor Jeb Bush, a brother of the US president, were to witness the launch at the space center near Cape Canaveral, Florida.

Should Tuesday's launch be called off, NASA still has until the end of the month to send Discovery into orbit so it can hook up with the orbiting ISS. After that, the next window for a daytime launch will be in September.

NASA will not launch the shuttle if there is thunderstorm activity within 20 nautical miles (37 kilometers) as this could affect an eventual emergency landing.

If such a landing were necessary, the shuttle could return to the Kennedy Space Center, or head to a base on the other side of the Atlantic, either in France or in Spain.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.

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