Blast off in Florida after Wednesday's aborted launch
Nasa's space shuttle Discovery has blasted off from the Kennedy Space Center in Florida on a 14-day mission to the International Space Station.
Its crew will deliver and install the space station's fourth and final set of solar arrays, which will provide the power for it to expand.
The seven astronauts include Koichi Wakata, who will be Japan's first long-term resident on the space station.
The shuttle's launch was postponed last month because of mechanical problems.
Electricity from the new solar arrays will support the expansion of the crew to six people.
It will also provide the power necessary to fully exploit the science labs now attached to the ISS.
Currently, the normal live-aboard complement is three individuals; and the station partners want to double this in May.
The mission is due to feature four spacewalks to help install the S6 truss segment to the starboard, or right, side of the station and the deployment of its solar arrays.
Koichi Wakata: The first Japanese long-duration ISS resident
Discovery's astronauts will also replace a failed unit for a system that converts urine to drinking water.
Another key task is ISS crew rotation. Discovery will drop off the Japanese space agency's (Jaxa) first resident crew member.
Discovery's delayed flight is the 125th to be made by a shuttle; the 28th to the ISS; and the 36th flight for Discovery itself.
Once the final truss segment is installed, the station's backbone - which supports not just the arrays, but radiators and other equipment - will be 102m long.
When viewed from the Earth's surface shortly after sunset, the ISS appears as a very bright star moving swiftly across the sky. The addition of a larger reflective area will make the platform an even more brilliant spectacle.
Altogether, the station's arrays can generate as much as 120 kilowatts of usable electricity, says Nasa.
The addition of the final set of solar arrays will nearly double the amount of power available for scientific experiments aboard the station - from 15kW to 30kW.
Eight more flights are required to finish construction of the station and to fill it with supplies prior to the retirement of the shuttle fleet in 2010.
Nasa also plans one additional shuttle mission to repair and upgrade the Hubble Space Telescope.
The agency is still awaiting the appointment of an administrator following the departure of the Mike Griffin. President Obama has yet to fill the post.
Discovery's mission had earlier been delayed by several weeks to give engineers time to investigate the cause of a fractured fuel valve on the last shuttle mission.
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