NASA will send its final space shuttle into orbit this summer, when Atlantis lifts off from Kennedy Space Center for a 12-day mission to the International Space Station.
The mission will garner much attention for what it represents -- the 135th and final flight of NASA's 30-year space shuttle program. But also important is the work that the four-member crew will be doing to ready the International Space Station for the post-shuttle-program era.
"The single biggest purpose of the mission is to provide sufficient supplies to get through 2012 without having to rely on any of the commercial providers that are emerging into the market," said Kwatsi Alibaruho, NASA's space shuttle flight director.
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The end of NASA's shuttle program won't mean the end of flights to the space station. Other countries, including Russia, Japan and European nations, will continue to haul cargo and ferry astronauts to the orbiting outpost.
But there are certain tasks that only the NASA space shuttles -- with cargo bays large enough to carry massive, heavy equipment into orbit -- can accomplish. Over the years, the fleet has carried modules, radiators, robotics and other hardware to the space station.
Next month, Atlantis will haul about 8,000 pounds of supplies to the International Space Station: a power unit for in-space treadmills, spare parts for various space station systems, water sampling kits, laptop computers, containers, filter tanks, clothes and food. It is scheduled to launch on July 8.
Also aboard will be a 650-pound module equipped with tools that are designed to refuel orbiting satellites. The module will be delivered to the space station, where it will start performing mock refueling missions in conjunction with the Dextre robot in December. Dextre is a Canadian robot with nine-foot long arms. The module has tools that Dextre will use to start a series of tests.
"It's a big complicated box with lots of tools and lots of satellite-like appendages on it, and it's 4-foot by 4-foot by 4-foot," said Frank Cepollina, a NASA engineer who works on the module. "What we are really trying to do is understand and develop the robotic technology and a robotic technique to repair and maintain spacecrafts in orbit."
Fuel is a determining factor in how long satellites can orbit. There are more than 400 satellites in orbit, mostly communication satellites. In a 10-year period, an average of 88 satellites fail.
"And you want to have repair capability and refueling capability, especially if you're a million miles from Earth," Cepollina said.
Space shuttle astronauts will also perform one final spacewalk during the mission, to remove a failed pump module for the station's two-part cooling system.
"This is a very important component to get back home intact," Alibaruho said.
The mood at Johnson Space Center, where the crew is deep into ensuring flight readiness for the mission, is bittersweet, Alibaruho said. He noted pride and determination, but also a touch of sadness.
"Many of the people who have in their hand a layoff notice are expected to fly this last mission," he said. "So there's a certain heaviness of heart going into it."
This article is reproduced with permission from PBS NewsHour. It was first published on June 27, 2011.