(CNN) -- After weeks of delay, the space shuttle Discovery is finally ready for a Wednesday evening liftoff and a two-week mission to the international space station.
Space shuttle Discovery readies for launch, scheduled for Wednesday night.
"We're not tracking any issues, so the team is anxious to go," Launch Director Mike Leinbach said at a pre-flight briefing.
The launch was delayed by a month while teams of engineers worked through concerns over hydrogen valves in the engine compartment. Problems with one of the three valves on the last shuttle flight raised the launch team's anxiety level.
NASA spent the past four weeks investigating paper-thin cracks in the valves and whether flying with those cracks would be too risky. In the end, all three of Discovery's valves were replaced, said Space Shuttle Program Manager John Shannon.
"We had sensed that we would get to this point. It's just one of those problems you just have to keep working at, and you have to keep doing the research, the analysis, the real hardware tests. And finally we got to that point," he said.
This will be the 125th shuttle flight and the 36th for Discovery. The two-week mission will include four spacewalks to install the 31,000-pound final truss segment with two solar array wings. The final segment completes the backbone of the station, and the set of solar arrays will convert solar energy to electrical power, providing the capacity to generate enough power to maintain a full crew of six and increase scientific research on the station.
Japanese astronaut Koichi Wakata will be on STS-119's seven-member shuttle crew. He'll be spending the next couple of months on the space station, replacing American astronaut Sandra Magnus, who returns to Earth when Discovery comes home. A stuffed duck will be accompanying Wakata to space as a memento of his hometown of Saitama, Japan.
The crew is also bringing up a couple of flags, including a green one representing the Andretti Racing Team. Pilot Tony Antonelli is expected to serve as the starter for a race after the shuttle's flight. Eight chocolate bars are going up too but are unlikely to come back.
For the nation's educators, this is an important flight. Two of the mission specialists, Joseph Acaba and Richard Arnold, are former middle school and high school teachers. Both are making their first space flights. and both will make spacewalks. Both men joined the astronaut corps in 2004.
Shuttle Cmdr. Lee Archambault has flown once before, as has Mission Specialist Steve Swanson. It's the first flight for Pilot Tony Antonelli and the third for Mission Specialist John Phillips.
The weather for the 9:20 p.m. EDT launch is expected to be nearly perfect. The Air Force meteorology team is forecasting a 90 percent chance of excellent launch conditions. Emergency landing sites at three overseas locations are also forecasting good weather, good to know in the event a problem forced the mission to abort after liftoff.
There are nine shuttle flights scheduled before NASA retires the three space shuttles in 2010. Eight missions are slated to complete the construction of the international space station, and one is dedicated to maintenance and upgrades to the Hubble Space Telescope.