After watching a nearby storm Friday morning while crews were fueling the space shuttle Endeavour, NASA decided to cancel the shuttle's scheduled launch due to a technical problem with a heater.
The space shuttle was scheduled to lift off for one last ride into earth's orbit at 3:47 p.m. Friday from NASA's Kennedy Space Center located at Cape Canavera, Fla.
Forecasters had put the odds of acceptable weather at the time of the launch at 70 percent.
NASA spokesman George Dillard says the next try will be Sunday at the earliest.
NASA reported earlier that two heaters on an auxiliary power unit were not working. Engineers could not understand the problem, and the launch was halted
The shuttle's launch was to also mark a major milestone in the recovery of Rep. Gabrielle Giffords, D-Ariz. Her husband, U.S. Navy Captain Mark Kelly is the commander of the mission which is the national space agency's next to last shuttle flight.
Kelly and his crew were on their way to the launch pad, when NASA halted the countdown. The astronauts' van returned the astronauts to crew quarters.
Kelly is married to wounded Giffords, who was shot in the head in January, left rehab in Houston behind to attend the afternoon liftoff.
She was to be at the space center to witness the shuttle's launch with about 45,000 other guests.
President Barack Obama and his entire family was also planning to attend, but had not arrived when NASA cancelled the flight.
Once the countdown is resumed and the shuttle lifts off from Cape Canaveral, Endeavour will rendevous with the International Space Station. The shuttle will carry one of the most expensive payloads in NASA's 30-year shuttle history -- a $2 billion particle physics detector that will seek out antimatter and dark energy across the universe.
NASA is ending the shuttle program this summer, after one last trip by the shuttle Atlantis. Obama has set the space agency on the path to study asteroids and ultimately the planet Mars.