Senior managers met Friday and agreed unanimously on the launch date. They determined that a leaky helium valve aboard Discovery would pose no safety concerns.
Discovery will haul up spare parts and extra supplies for the International Space Station. During the two-week mission, President Barack Obama will travel to Florida to discuss his post-shuttle plans for NASA.
Obama supports deep-space exploration, but has yet to lay out a destination for astronauts or a timetable. He axed the Constellation moon program set up by his predecessor.
The leaky valve - part of the system for maneuvering the shuttle in orbit
- would not close during testing earlier this month. It's typically open anyway, and everything else in the system appears to be working fine. Nonetheless, some engineers asked managers to look further into the matter, to make sure there was no pressure to keep the remaining flights on track and no distraction because of the failure.
Shuttle program manager John Shannon said there's no reason, right now, why the final four missions can't be completed by the end of September. He acknowledged something could crop up to delay the remaining flights. "We almost had one here," he said, referring to the valve trouble.
NASA's inspector general office reported Thursday that the last shuttle flight may well slip into 2011, based on history and various calculations.
One potential threat to the flight schedule: the Alpha Magnetic Spectrometer, a major science experiment undergoing testing in the Netherlands. The particle physics detector is supposed to be launched aboard Endeavour at the end of July, but may not be ready in time.
"We take each flight one at a time," Shannon said.
Launch time on April 5 - the day after Easter - will be 6:21 a.m. Eastern.
On the Net: