(CNN)  -- Launch of the space shuttle Discovery has been delayed at least a week, NASA has announced.



Discovery moves atop the crawler transporter in Cape Canaveral, Florida, on January 14.



The shuttle will now lift off no earlier than February 19 because of concern over a valve in the main engine. A decision on the launch date will be made February 12, after more analysis and testing of the part.



NASA said Tuesday night: "The valve is one of three that channels gaseous hydrogen from the engines to the external fuel tank. One of these valves in shuttle Endeavour was found to be damaged after its mission in November. As a precaution, Discovery's valves were removed, inspected and reinstalled."



This will be the shuttle's 28th mission to the international space station.



The mission will deliver the final set of solar arrays needed to complete the station's complement of electricity-generating solar panels. They will help support the station's expanded crew of six in 2009.



"More crew means that we'll have to run more life support equipment, more crew support equipment -- toilet facilities, water processing equipment and all of that stuff," Kwatsi Alibaruho, the lead space station flight director for the mission, said on NASA's Web site. "We'll have to run more of all of that, so we need additional power."



The expanded capacity will mean more hands to perform science experiments. The mission also will include four spacewalks.
What is NASA worried about? When will Discovery lift off? What is the space agency concerned about? How many missions have been to the space station? What is the name of the US Space Agency? What will lift off no earlier than February 19th? How soon could Discovery launch? What was the agency concerned about? How many trips has Discovery made to the International Space Station? What is Discovery delivering this time? What will the mission deliver?
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question: What is NASA worried about?, answer: a valve in the main engine. | question: When will Discovery lift off?, answer: February 19 | question: What is the space agency concerned about?, answer: a valve in the main engine. | question: How many missions have been to the space station?, answer: 28th | question: What is the name of the US Space Agency?, answer: NASA | question: What will lift off no earlier than February 19th?, answer: space shuttle Discovery | question: How soon could Discovery launch?, answer: no earlier than February | question: What was the agency concerned about?, answer: a valve in the main engine. | question: How many trips has Discovery made to the International Space Station?, answer: 28th | question: What is Discovery delivering this time?, answer: final set of solar arrays | question: What will the mission deliver?, answer: the final set of solar arrays needed to complete the station's complement of electricity-generating solar panels.