By Irene Mona Klotz
at the Kennedy Space Center, Florida
After more than two years of heartache, hard work and heavy spending, the US space agency says it will be ready on 13 July to launch its first space shuttle since the Columbia tragedy.
The shuttle has been grounded for two-and-a-half years
"It's just an outstanding day to be this close to getting the shuttle flying again," Nasa launch director Michael Leinbach told reporters on Thursday at the end of a two-day flight review. "It's a great, great feeling."
But earlier this week, a panel monitoring the return to flight said the agency had failed to meet three of 15 recommendations made by the Columbia Accident Investigation Board (CAIB) for the safe resumption of shuttle journeys.
But Nasa administrator Michael Griffin said Discovery was fit for launch.
"Based on a very thorough and very successful flight readiness review, we're currently 'go for launch' of Discovery on 13 July," he announced.
Discovery's seven-member crew, headed by veteran astronaut Eileen Collins, arrives at the Florida spaceport for final flight preparations on 10 July.
Before the Columbia accident in February 2003, much of the tension associated with sending a shuttle into orbit dissipated after a successful launch. But the Columbia disaster demonstrated that any stage of the mission carries great risks.
Columbia and its crew of seven perished as they flew home for landing, the result of undetected damage from a debris impact during lift-off that had no effect on the ship in space.
Since that day, Nasa has doggedly pursued as many options as possible to prevent debris impacts, detect damage and develop back-up plans for saving the crew even if the ship cannot return to Earth.
Although managers pledged that Discovery will be the safest shuttle launched to date, there will be no victory dance until the vehicle is safely back on the ground.
"I personally don't think we're going to be doing any celebrating until we have wheels stop on the landing," Dr Griffin said.
The associate administrator for space operations, William Readdy, added: "The celebration isn't about weighing anchor. The [celebration] is about when Discovery's at anchor after a successful mission."
Discovery is to spend a week at the International Space Station, which has been operating one crew member short since Nasa grounded the shuttle fleet for repairs.
The shuttle will not only be delivering much-needed supplies, it will also ferry a new gyroscope, which is part of the outpost's fuel-free steering system.
Nasa says, however, the primary purpose of the mission is to test how well the safety upgrades implemented after the Columbia accident perform in orbit. A second test flight is targeted to follow in September.
"I'm extremely confident in the safety of this vehicle," shuttle programme director Bill Parsons said.
"I can't say I'm not going to be tense, I'm not going to be concerned, but I believe we have done everything right," Parsons said.
Setting the launch date for the first flight since Columbia was an emotional moment, as well as a key milestone for the agency. When managers were polled about their readiness to launch and everybody said 'go', there were cheers and a standing ovation, said Nasa spokesman Kyle Herring. Bill Parsons added: "I had a lump in my throat."
Nasa's next challenge may be a battle of patience. As managers met with reporters to announce the launch date, they had to raise voices to be heard over the pounding rain and thunder booms, which are common fare for Florida in the summer.
"Launching in the middle of the afternoon will be a real challenge," Michael Leinbach said.
Discovery's launch window extends until 31 July.