The Legacy of Endeavour

Space shuttle Endeavour
Bathed in xenon lights, space shuttle Endeavour moves along the crawlerway from the Vehicle Assembly Building to Launch Pad 39A at NASA's Kennedy Space Center in Florida. Riding atop a crawler-transporter attached to its external fuel tank and solid rocket boosters, Endeavour's last scheduled 3.4-mile trek to the pad, known as "rollout," took just less than eight hours. Image credit: NASA/Terry Zaperac

Space shuttle Endeavour has spent 19 years pushing boundaries, and its final mission will allow that legacy to live on.

Among Endeavour’s missions was the first to include four spacewalks, and then the first to include five. Its STS-67 mission set a length record almost two full days longer than any shuttle mission before it. Its airlock is the only one to have seen three spacewalkers exit through it for a single spacewalk. And in its cargo bay, the first two pieces of the International Space Station were joined together.

On STS-134, however, it will help push boundaries of a different sort as it delivers a new, cutting edge science experiment to the space station: the Alpha Magnetic Spectrometer.

“The AMS is an amazing story all by itself,” said Gary Horlacher, lead space shuttle flight director for the mission. “They’ve been working on this for well over 15 years now. It’s bigger than a VW bug, and it will be able to look at things that the other observatories aren’t even looking at. It is, without a doubt, going to continue to rewrite our future as we try to figure out our past.”

The Alpha Magnetic Spectrometer is a state-of-the-art, high energy particle physics experiment built in Geneva by a collaboration of 16 different countries. It will search for clues on what the universe is made of and how it began, the origin of dark matter, antimatter and strangelets, pulsars, blazers and gamma ray bursters. And that’s just what the scientists know to look for.

“I am quite confident that once we start measuring data in space, we will find things that we never anticipated,” NASA’s AMS Project Manager Trent Martin said. “And those things will lead to potential new areas of study, new areas of science and maybe even redefine some of the physics books.”

It’s a new area of investigation for International Space Station science, and the only experiment of its type in the universe; although there are detectors on the ground trying to answer the same questions, they’re limited to the particles that make it through the Earth’s atmosphere, or that they create themselves. Meanwhile several telescopes are already in space, but they can only measure light, not particles.

Thanks to the extension of the International Space Station program, the AMS will be sifting through the cosmos for years after Endeavour has retired. And some of the other aspects of Endeavour’s mission will help ensure that the station is able to continue providing a home for it and the many other science experiments going on in space.

After AMS is installed on station’s truss during the fourth day of the mission, a pallet of spare parts will be added to the space station on the mission’s flight day 5. Then there will be a string of spacewalks – the last spacewalks to be performed by a shuttle crew – dedicated to getting the station in the best possible shape for the end of the space shuttle program.

The spacewalkers will top off a leaky ammonia loop and lubricate one of the massive joints that turn the station’s solar array wings. They’ll also add to the Russian segment of the station a handhold for the station’s robotic arm, extending the arm’s range to that area, and make a permanent home on the station’s truss for the shuttle robotic arm’s 50-foot long boom extension, so that it can be left behind to give the station’s arm a greater reach.

None of the tasks are urgent – the ammonia leak is very small and wouldn’t really need to be dealt with for another two years or so, for instance, and the joint would eventually need the lubrication but doesn’t yet. However, getting these things done is easier when there’s a shuttle present – it costs the station less oxygen, and the extra hands on deck improve efficiency. So, it’s better to get them done now.

“These spacewalks are kind of a catch all – an accumulation of the stuff we haven’t been able to get to on the last several flights,” Derek Hassmann, lead station flight director for the mission, said. “But it’s all about getting the station in the best posture to give it the most margin and most capability for a long life after we stop flying shuttles.”

But for all that one of the primary focuses of the mission is preparing the station for the shuttle’s final wheel stop, everyone agrees that the subject of the end isn’t one that they’ve spent much time contemplating. Horlacher and Hassmann say they’ve worked hard to ensure that they disconnect from the commotion associated with STS-134 being Endeavour’s final flight, and focus on making it every bit as successful as Endeavour’s first. And the mission’s commander, Mark Kelly, agreed.

“It is what it is,” he said. “I’ll think about it more after the mission. We’re just going to try to do the job and do it safely.”

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