LIVE IMAGES: The images above are from live video feeds in the Launch Complex 39 area at Kennedy Space Center. They will automatically refresh to the most up-to-the-minute image every 30 seconds.Endeavour's external tank is now being topped off and engineers have detected none of the type of dangerous gaseous hydrogen leaks that forced NASA to scrub consecutive launch attempts on June 13 and June 17.
Seven astronauts remain scheduled to blast off from Kennedy Space Center at 6:03 p.m. The weather forecast calls for a 60 percent chance conditions will be acceptable for launch and no technical issues are being worked at this time.
The loading of the 15-story external tank reached the 98-percent-full level around 10:45 a.m. Engineers from this point forward will continue topping off the tank to keep the propellant load at proper levels as some of the cryogenic fuel "boils off" -- or turns from a liquid to a gaseous state.
Supercold liquid oxygen and liquid hydrogen have temperatures of Minus 298 degrees Fahrenheit and Minus 423 degrees Fahrenheit, respectively, and some boil off always occurs.
Keeping the tank topped off is critical to making certain the shuttle has enough propellant to launch into orbit. Too low a level would lead to an unprecedented emergency landing -- likely at an abort landing site in Spain or France.
Dangerous gaseous hydrogen leaks were detected around a vent line as fuel-loading operations reached this exact point prior to Endeavour's first two launch attempts last month.
NASA subsequently made repairs to the line that were then verified in a tanking test on July 1.
No significant leaks were spotted during fuel-loading operations prior to weather scrubs on Sunday and Monday.
NASA engineers nonetheless will be keeping close tabs on the repaired vent line assembly throughout the remainder of the countdown.
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