Twice delayed in June, NASA again scratches its mission to the International Space Station after 11 lightning strikes are recorded in the launch area. After a check of all systems, NASA hopes to finally get the mission under way July 12.

NASA called off the launch of the space shuttle Endeavour for a third time July 11 after lightning strikes in the Cape Canaveral area prompted the space agency to move the liftoff to July 12. The mission to deliver equipment to the International Space Station was scratched twice in June due to a mysterious launch pad hydrogen gas leak that appears to be resolved.

NASA reported 11 lightning strikes during the storms that have plagued the Florida coast for weeks. None of the strikes hit the shuttle or its external tank and solid rocket boosters, but there were strikes to the lightning mast and water tower. Two of the strikes were strong enough to trigger an evaluation by NASA engineers.

"We need to be 100 percent confident that we have a good system across the board," said Mike Moses, Endeavour's mission management team leader, at a July 11 briefing. "We've seen nothing so far that indicates anything was actually affected by the lightning strike. But we have to check, and that's what takes time."

The July 12 launch is now set for liftoff at 7:13 p.m. EDT. The weather forecast calls for a 60 percent chance of favorable launch conditions.

The Endeavour's original launch date was June 13, but it was canceled 5 hours before launch due to a potentially dangerous vent line hydrogen gas leak. NASA tried again on June 17 but called off the mission when the hydrogen leak reappeared. The leaks were similar to one that NASA encountered while trying to launch Discovery four months ago.

That flight was delayed four days because of the problem and shortened as well. Atlantis, however, encountered no such trouble during its countdown in May for the Hubble Space Telescope repair mission.

Since the Endeavour crew stood down June 17, NASA engineers have pinpointed the leak to a plate that attaches the vent line to Endeavour's external fuel tank. The plate was slightly misaligned, allowing a small leak to happen during the fueling process. After NASA completed a fueling test July 1, the space agency declared the problem fixed.

"This one I feel really good about, that we've got that problem licked and we're not going to see another GUCP [Ground Umbilical Carrier Plate] leak again on the next launch attempt," said Moses.

Endeavour is now scheduled to dock at the ISS July 13 with a cargo bay full of work that includes what Endeavour Commander Mark Polansky calls "really big pieces of equipment" and will require five spacewalks over the course of the 16-dasy mission. A literal "front porch" for the ISS, the Kibo laboratory complex will allow for space-exposed science experiments.

"It's a real exciting mission. We are the last mission that is taking up Japanese hardware on a space shuttle ... really big pieces of equipment that we're going to go ahead and leave behind on the space station for construction," Polansky said in a preflight interview.

Also inside Endeavour's cargo bay will be an integrated cargo carrier holding several pieces of spare equipment for the space station. Most of it - a spare space-to-ground antenna, a spare linear drive unit and a spare pump module - will be stored on an external storage platform on the station's truss. But six batteries for the station's oldest solar array will be installed.

Once the Endeavour reaches the ISS, things will be as busy inside the shuttle and space station as the spacewalkers, with all three of the available robotic arms being put to use, sometimes all on the same day. The shuttle's Canadarm and the station's Canadarm2 will be put through their regular paces for surveys, unloading cargo and moving equipment and spacewalkers around, and a new Japanese robotic arm will be making its debut to transfer science experiments.

"It's certainly really exciting for JAXA [Japan Aerospace Exploration Agency]," said Polansky. "For them, this is the last of their hardware that's going to be permanently attached to the space station. This completes their series."

The mission also marks another milestone for JAXA, with Japanese flight controllers on the ground operating their own berthing mechanisms for the first time. The Kibo external facility will never need to be connected to anything but a Japanese-built module, so the Japanese were free to use any berthing mechanism they wanted.

"Before, even when we had pieces of hardware that were built by someone else, we have, here in the U.S. control center, still maintained a lot of the technical leadership," said lead Station Flight Director Holly Ridings. "In this case, they truly have technical leadership for some of the things that must work to make the mission a success. It's unique."