The U.S. space shuttle Discovery is scheduled to lift off from the Kennedy Space Center in Cape Canaveral, Florida late Wednesday, the first of five shuttle flights planned for this year to the International Space Station.
Discovery's mission this week, which has been delayed for about a month so engineers could repair faulty fuel pressure valves, will carry a crew of seven astronauts - including one from Japan - to install the fourth and last pair of solar power panels to the space station.
STS-119 will be the 28th shuttle mission to the International Space Station. It will deliver the final set of solar arrays needed to complete the station's electricity-generating solar panels to support an expanded crew of six people.
Shuttle launch director Mike Leinbach told reporters recently he is happy about the launch.
"I'll just tell you, the mood is very, very upbeat," Leinbach said. "Compared to a couple of weeks ago, when we didn't know exactly where we were going to get with the launch date, now we have one and everyone feels really good. Team Discovery is ready to execute. And I feel really good about their attempt [to lift off] Wednesday night."
The 14-day mission was originally set for launch on February 12. However, a number of delays were imposed, so NASA engineers could replace Discovery's three fuel pressure valves, which control the flow of hydrogen from the shuttle's three main engines.
During a shuttle launch last November, one of three valves cracked - raising concerns about the safety of future missions.
Shuttle program manager John Shannon says all three valves were examined using a new technique to determine whether normal use during previous missions had caused the problem.
"And two of them [the valves] were clean, and one of them showed two cracks in it," Shannon said. "And that was a little bit of a surprise to us. And so we screened the three valves that we had taken off of Discovery that had the 12 flights apiece. And the first one we looked at had a crack in it. And the next two did not have cracks in them. So we were able to put together with a very high confidence method a set of three valves and a flight spread that we could put in Discovery and have a lot of confidence that they did not have initiating cracks."
Shannon says that even if cracks do occur during liftoff, any damage that might occur would not affect the mission.
Discovery's crew is scheduled to install a set of solar arrays on the International Space Station - including two movable solar wings - that will track the sun for power. The four sets of panels will generate 84-to-120 kilowatts of electricity - enough to provide power for more than 40 average U.S. homes. The newest set of solar arrays will provide power for additional scientific experiments and enable the station to expand its permanent crew to as many as six.
The shuttle crew is scheduled to conduct as many as four spacewalks to install the solar arrays and advance further construction, possibly installing a Global Positioning System antenna to help guide a Japanese-built transfer vehicle to the station later in the year.
Among the seven-person Discovery crew is Japanese astronaut Koichi Wakata - a 45-year old Japan airlines aerospace engineer who will become the first Japanese resident onboard the space station, replacing American Sandy Magnus.
NASA hopes to complete the space station next year and retire its shuttle fleet after nearly 30 years of service.