NASA managers cleared the shuttle Endeavour for launch Sunday after a 24-hour delay to make sure launch pad lightning strikes Friday caused no damage to critical systems. With a clean bill of health and forecasters predicting generally good weather, engineers loaded the shuttle's external tank with rocket fuel to set the stage for liftoff.
Wearing bright orange pressure suits, commander Mark Polansky, pilot Douglas Hurley, Canadian flight engineer Julie Payette, David Wolf, Christopher Cassidy, Thomas Marshburn, and space station flight engineer Timothy Kopra began strapping in for launch a few minutes before 4 p.m. EDT.
Liftoff is targeted for 7:13:55 p.m., roughly the moment Earth's rotation carries the launch pad into the plane of the International Space Station's orbit.
The primary goals of the 16-day, five-spacewalk mission are to attach an experiment platform to the Japanese Kibo module, to replace aging solar array batteries, and to deliver critical spare parts. In addition, Kopra will replace station flight engineer Koichi Wakata, launched to the outpost last March.
Endeavour was grounded twice last month when leaks developed where a 7-inch gaseous hydrogen vent link attaches to the side of the shuttle's external tank. The leaks showed up when the hydrogen section of the tank was nearly full and the hardware was chilled to ultra-low temperatures.
After the second scrub June 17, engineers traced the problem to a slight misalignment in the vent port housing on the side of the tank. A more flexible two-part seal was installed and changes were made to the vent line mounting plate to ensure a tight fit. The repairs were tested July 1 during a fueling test and the vent line system was leak free.
NASA then reset launch for Saturday but managers ordered a 24-hour delay to assess the potential effects of multiple lightning strikes at the launch pad during a severe thunderstorm Friday. Early today, engineers concluded there were no lightning-related problems with any of the shuttle's systems and Endeavour was cleared for launch.
Forecasters are predicting showers and thunderstorms inland with just a few clouds at the launch site at 3,000 feet, a scattered deck at 25,000 feet, and winds out of the southeast at 8 knots with gusts to 12. There is a 30 percent chance of showers or thunderstorms moving within 20 nautical miles of the launch site.
While shuttle engineers completed Endeavour's fueling, a Russian Progress supply ship carried out an automated re-rendezvous with the International Space Station, approaching to within about 30 feet of the lab complex to test docking system navigation aids on the upward-facing port of the Zvezda command module.
Antennas and cabling for the navigation system were installed during a spacewalk last month and Sunday's test cleared the new port for use later this year when a new Russian module will home in for an automated docking.
Updated at 4:15 p.m. EDT: Astronauts board shuttle; fueling completed with no problems; weather update; Progress docking test complete.