NASA's countdown clocks are ticking again for today's launch of space shuttle Endeavour.

"I'm really proud of our teams working so hard over the last couple of weeks," said NASA Test Director Jeff Spaulding. "All the teams here at Kennedy and all the other centers have done an outstanding job to get us ready for this launch on this historic and final flight of space shuttle Endeavour."

NASA was scheduled to launch the Endeavour on April 28 but the agency aborted the launch after the thermostat that controls the heater didn't kick on when it was called to do so. Technicians determined the failure was inside an aft load control assembly, which is a switchbox in the shuttle's aft compartment, and possibly its associated electrical wiring. The thermostat was replaced last week, along with a switch box containing a blown fuse.

Launch teams at Kennedy Space Center in Florida are not working any issues that would delay liftoff on Monday, May 16 at 8:56 a.m., according to the latest news release by the agency.

Shuttle Weather Officer Kathy Winters has forecasted a 70% chance of having favorable weather for Endeavour's liftoff scheduled for Monday. According to the forecast, there may be some storm disturbance around the time the rotating service structure is to be rolled back, now scheduled to begin at noon on Sunday, but launch day is looking good for Kennedy and also for booster recovery and abort landing sites.

The six astronauts for space shuttle Endeavour's STS-134 mission to the International Space Station returned to the Kennedy Space Center on Thursday.

The crew members for space shuttle Endeavour's STS-134 mission are Commander Mark Kelly, Pilot Gregory H. Johnson and Mission Specialists Michael Fincke, Greg Chamitoff, Andrew Feustel and European Space Agency astronaut Roberto Vittori.

The crewmembers' families are expected to arrive in the weekend for the send-off. Mr. Kelly's wife, Arizona Rep. Gabrielle Giffords, who was wounded in the head in January at a political event in Tucson, is expected to leave rehab in Houston to travel to Florida for the second launch attempt.

NASA Test Director Jeff Spaulding expects a crowd of 500,000 to see Endeavour's final voyage. This would be the space shuttle's 25th journey.

During the 16-day mission, Endeavour and its crew will deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre.

NASA is wrapping up its 30-year shuttle program, with the launch of Atlantis in July.