Endeavour Crew Saddles Up for Third Attempt at ISS Mission

The Endeavour crew arrived at the Kennedy Space Center July 7 for a third try at a major buildout of the ISS (International Space Station). NASA twice scratched the mission in June due to a mysterious launch pad hydrogen gas leak that appears to be resolved. Liftoff for NASA mission STS-127 and its seven-person crew is scheduled for July 11 at 7:39 p.m. (EDT).

Endeavour is 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 mission. The primary purpose of the mission is to deliver the final permanent components of Japan's Kibo laboratory complex, a literal "front porch" on the ISS for space-exposed science experiments. After the crew's frustrating June, Polansky said, "I can tell you that this crew and the entire operations team are both eager and ready to get to work. Hopefully the next time we talk to you will be from orbit."

The Endeavour's original launch date was June 13 but it was cancelled five hours before launch due to a potentially dangerous vent line hydrogen gas leak. NASA tried again on June 17 but called the mission when the hydrogren 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.

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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," Mike Moses, head of the shuttle's mission management team, told reporters.

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."