The mission is to deliver the final set of power-generating solar array wings and a new crew member to the International Space Station, said NASA.
"Discovery's STS-119 flight is carrying the space station's fourth and final set of solar array wings, completing the station's truss, or backbone," said the American space agency. "The arrays will provide the electricity to fully power science experiments and support the station's expanded crew of six in May."
According to the space organisation, the 13-day mission will feature three spacewalks to help install the S6 truss segment to the starboard. The flight also will replace a failed unit for a system that converts urine to potable water.
"It's truly an honour to be part of this team representing NASA, the nation and the international partners," said Commander Lee Archambault. "See you in a couple of weeks."
Archambault's team mates include Pilot Tony Antonelli and Mission Specialists Joseph Acaba, Steve Swanson, Richard Arnold, John Phillips and Japan Aerospace Exploration Agency astronaut Koichi Wakata.
According to NASA sources, Wakata will replace space station crew member Sandra Magnus, who has been aboard the station for more than four months.
Former science teachers Acaba and Arnold are now fully-trained NASA astronauts. They are making their first journey to orbit on the mission and will to step outside the station to conduct critical spacewalking tasks.