CAPE CANAVERAL, Fla. - Endeavour's final shuttle flight has been delayed again.
The shuttle will now blast off no earlier than May 16. NASA announced the new date Friday.
Endeavour, which was scheduled to fly to the International Space Station last Friday, was grounded by a heater malfunction. The trouble was traced to a switch box.
Engineers discovered a blown circuit inside. A new box has been installed, but more testing is needed.
The two-week mission will be led by commander Mark Kelly, the husband of wounded Rep. Gabrielle Giffords.
The congresswoman's staff says she will return to Cape Canaveral for another launch attempt.
NASA managers are holding open an option to extend the mission by two days to give the shuttle crew time to help out with needed station maintenance, reports CBS News space analyst Bill Harwood.
Complicating mission planning, three of the space station's six crew members - Dmitry Kondratyev, Paolo Nespoli and Catherine Coleman - are scheduled to return to Earth May 23 aboard a Russian Soyuz spacecraft, leaving the lab understaffed until three replacements arrive June 9.
The primary goals of Endeavour's flight are to deliver a pallet of spare parts and to install a $2 billion particle physics experiment on the station's power truss. The Endeavour astronauts also plan to stage four spacewalks to perform critical maintenance, but the launch delay and Soyuz departure are expected to result in a major flight plan revision and the EVA schedule is not yet clear.
Endeavour was grounded during the final hours of a launch countdown April 29 when one of two "strings" of fuel line heaters used by one of the shuttle's three hydraulic power units failed to power up normally. While the system can safely operate with a single string, a subsequent failure could result in a fuel line rupture, knocking auxiliary power unit No. 1 out of action and possibly contaminating the aft engine compartment with toxic hydrazine.