The space shuttle Endeavour's crew will return to the pad in the wee hours Monday morning for another launch attempt, following Sunday morning's false start. Mission managers have rescheduled the launch for 4:14 a.m. Eastern Standard Time Monday.
The decision to scrub Sunday’s lift-off came after weather at the launch site in Florida took an unexpectedly cloudy turn.
The space ship itself "was top notch" throughout the countdown, said assistant launch director Peter Nickolenko following the decision at 4:30 a.m. Eastern Standard Time to stand down. The count was free of technical glitches.
But outside, "real conditions were a little different than the tools seemed to forecast," he added, referring to the forecasting models used by the center's weather team.
Earlier forecasts had indicated an 80 percent chance of favorable weather. But clouds moved in too low and too thick to allow the range-safety team to track the launch or to give astronauts a clear view of the runway at the Kennedy Space Center if they had to abort their ascent and return to the space center's runway.
The shuttles are gliders; a shuttle commander has only one try at landing.
During the pre-dawn hours, weather conditions teased the launch team – appearing to clear a little, only to cloud up again. After weighing information from ground observers around the site and from a training jet sent aloft to provide moment-by-moment observations of conditions over the pad and runway areas, managers decided that conditions were too dynamic to give them much confidence that the situation would improve during the remaining 10 minutes in the countdown.
Notified of the decision to scrub the launch, shuttle commander George Zamka replied, "Sometimes you just got to make the call.... We'll give it another try tomorrow night."
Endeavour and its crew aim to deliver and install the last major US-funded module to the International Space Station, which will house life-support and sanitation equipment, as well as exercise gear for the astronauts. When installation is complete, the module will include a seven-pane window, or cupola.
The cupola will allow station crew members to help guide the progress of spacewalks or tasks that require use of the station's robotic arm. And it will provide stunning views of Earth, as crew members use the exercise gear house in the module.
Endeavour's launch leaves only four more flights before NASA ends the shuttle program at the end of the year. Weather permitting, the orbiter's ascent should be visible along the US East Coast until Endeavour's main engines shut down about eight minutes into the flight.
Follow us on Twitter.