CAPE CANAVERAL, Fla. – NASA's countdown clocks began ticking again Friday for the next-to-last space shuttle launch, delayed two weeks ago by an electrical problem aboard Endeavour.
Forecasters put the odds of good weather for Monday morning's launch at 70 percent: the main concerns are stiff crosswind and low clouds.
NASA test director Jeff Spaulding said everything was on track this time around, and that the most likely culprit for last month's failed launch attempt was an exposed conductor on a thermostat.
The thermostat was replaced last week, along with a switch box containing a blown fuse.
Commander Mark Kelly and his five crewmates returned to Kennedy Space Center on Thursday. Their families will follow this weekend, including Kelly's wife, Arizona Rep. Gabrielle Giffords, who was critically wounded in the head in January at a political event in Tucson. She interrupted her rehab in Houston to travel to Cape Canaveral for the first launch attempt, and will do so again.
For the April 29 launch attempt -- on a Friday afternoon -- NASA had expected 700,000 or more people to jam surrounding roads and towns. A smaller crowd is anticipated for Monday's 8:56 a.m. try, possibly around the 500,000-mark, Spaulding said. That would still be larger than the 400,000 who turned out for Discovery's final voyage in February. Only one other shuttle flight remains, by Atlantis in July.
Endeavour -- making its 25th and final journey -- will fly to the International Space Station and deliver a $2 billion science experiment. Four spacewalks are planned during the 16-day mission.
In a space first, a Russian Soyuz capsule will depart the orbiting complex while Endeavour is there. The Soyuz will return to Earth with half of the six-person station crew, leaving the six shuttle astronauts and remaining three station residents to manage the work load.
NASA is wrapping up the 30-year shuttle program, under presidential direction to hand over orbital ferry trips to private companies. That frees up the space agency to concentrate on expeditions to asteroids and Mars.
Endeavour is the newest of NASA's three shuttles. It was built to replace the Challenger, lost in a 1986 launch accident.