CAPE CANAVERAL, FL (AP) - NASA has called off Friday's launch of space shuttle Endeavour because of a technical problem.
There is now a 48-hour hold on the launch, meaning Endeavour can't make its last trip into orbit until at least Sunday afternoon.
Commander Mark Kelly and his crew were on their way to the launch pad, when NASA halted the countdown. The astronauts' van did a U-turn, and returned the astronauts to crew quarters.
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.
Hundreds of thousands of people had converged on the Florida coast for prime viewing spots on Friday, including congresswoman Gabrielle Giffords. Her husband, astronaut Mark Kelly, is the commander of this mission.