NASA had hoped to launch in February, but spokesman Kyle Herring says they had to double check a few valves.
"The delay, simply, was to allow a team of engineers to evaluate a technical issue just to make sure they understood it before we would go flying and flying safely."
With the shuttle given the green light, it will head to space Wednesday carrying more solar panels as crews continue to work on the space station.
"This is the fourth set of U.S. solar array panels that will increase the electrical capability of the station as it continues to grow. And the crew will deliver that final trust segment and 240-foot long solar array pair."
The shuttle commander will also drop off a Japanese astronaut at the Space Station and pick up an American...who's been up there and will be coming home.
Bill Stamps, KUHF Houston Public Radio News.
Î¾Attired in training versions of their shuttle launch and entry suits, these seven astronauts pose for the STS-119 crew portrait. From the right (front row) are NASA astronauts Lee Archambault, commander, and Tony Antonelli, pilot. From the left (back row) are NASA astronauts Joseph Acaba, John Phillips, Steve Swanson, Richard Arnold and Japan Aerospace Exploration Agency astronaut Koichi Wakata, all mission specialists. Wakata is scheduled to join Expedition 18 as flight engineer after launching to the International Space Station on STS-119.