NASA - National Aeronautics and Space Administration

Space Shuttle Atlantis is ready to make its next flight, and its STS-115 mission will be an important milestone in the future of space exploration. Assembly of the International Space Station is about to resume.

Image to right: The STS-115 crew is scheduled to perform three spacewalks to install a new element on the space station. Credit: NASA

In its payload bay, Atlantis carries new solar power arrays for the ISS and another segment of the truss that supports the arrays and forms the backbone of the station. When the STS-115 crew docks with the space station, one of the astronauts' biggest tasks will be to install these items. It will mark the first time major new components have been added to the station in almost four years.

NASA is currently working to carry out the Vision for Space Exploration, a long-term plan that will lead to humans returning to the moon and then traveling onward to other worlds. One of the first steps has been taken -- returning the space shuttle safely to flight. Now, NASA is working to fulfill the mandate to complete the International Space Station by the time the shuttle fleet is retired in 2010. The space station will serve as an important platform for learning things about living in space that will be vital to exploration further from humanity's home planet.

Image to left: The P3/P4 truss segment the crew will install can be seen on the right side of this computer-generated image. Credit: NASA

During the STS-115 mission, the crew is scheduled to conduct three spacewalks to install and activate the truss segment and solar arrays. The P3/P4 truss segment that Atlantis carries is 45 feet long, and will extend the station’s truss farther out to its port (or left) side. The truss will eventually contain 11 segments and will span more than 300 feet. Once the P3/P4 element is installed, solar arrays will be deployed that will have a wingspan of almost 240 feet. These arrays will provide about a quarter of the station's power when the ISS is completed. On Earth, the P3/P4 segment weighs almost 35,000 pounds, making it one of the heaviest payloads launched to the station.

Related Resources + NASA STS-115 Mission

The commander of the STS-115 mission is Brent Jett, who is no stranger to delivering solar arrays to the International Space Station. In 2000, he commanded the STS-97 shuttle mission, which delivered the first set of U.S. arrays to the station. STS-115 is his fourth spaceflight. The pilot for the mission is Chris Ferguson, and mission specialists are Joe Tanner, Dan Burbank, Heidemarie Stefanyshyn-Piper and Steve MacLean, of the Canadian Space Agency. Ferguson and Stefanyshyn-Piper are both making their first spaceflight.

"Since the Columbia accident, the two missions since then -- 114 and 121 -- have been focused a lot on the Return to Flight objectives," Commander Jett said. "Now those missions have been very valuable to the station as well -- logistically, making repairs for the station, adding a third crewmember. But really, 115 is the return to the assembly sequence, and I think that's significant. We have a mandate to finish the station by 2010 and retire the shuttle. So we need to shift from the Return to Flight mode back to a more operational assembly sequence, where we're flying hopefully four to five times a year and completing the assembly fairly quickly."

Image to right: The STS-115 mission patch prominently features one of the solar arrays that will be deployed during the flight. Credit: NASA

Mission specialist Joe Tanner, who was involved in truss installation when he flew with Jett previously on STS-97, said he is excited about the future that his work on STS-115 will help make possible.

"I think there are great things ahead," he said. "I think going to the moon and beyond is part of human destiny. We are born to explore. We start it as soon as we can look with our eyes and use our hands and then crawl."

He added, "Human beings are meant to explore. We've been doing that in space in the U.S. program since 1961, and I just hope that we continue to do that."

David Hitt/NASA Educational Technology Services