The cosmic iron workers are back on the ground after their trip to the International Space Station. Next up: the electricians and the folks from heating, ventilation, and air conditioning.
The shuttle Atlantis and its six-member crew wrapped up a successful mission with a perfect predawn landing at the Kennedy Space Center in Florida Thursday. During its 11-day, 19-hour trip, the crew added a new segment to the station's "backbone," which included an array of solar panels 240 feet long. The panels will generate additional electricity critical to adding lab modules from Europe and Japan. The first of these is slated to arrive at the station in October 2007.
In addition, the crew accomplished a range of "get ahead" tasks to help smooth the way for the next phase of construction, which gets under way with the launch of Discovery, currently penciled in for Dec. 14.
"It's obvious to me that we are rebuilding the kind of momentum that we have had in the past and that we need if we are going to finish the space station," said NASA Administrator Michael Griffin during a postlanding briefing. "We have an awesome task ahead of us.... I think we're going to make it."
That's an assessment that undoubtedly brings a smile to the project's international partners.
"International partners, especially the Japanese and Germans, were crossing their fingers, hoping this mission would pan out," says Ray Williamson, with George Washington University's Space Policy Institute. "If NASA is successful at getting the space station completed, you'll see a lot more openness in Europe and Japan to collaborate with the US in new exploration efforts."
For December's mission, spacewalking astronauts are set to perform tasks that initiate the most complicated phase of station construction, mission planners say. In addition to delivering another truss segment, Discovery's crew will overhaul the electrical wiring and cooling-system plumbing to all of the major US components.
"It would be the equivalent to changing who delivers the electricity and water to your house – not just changing the source, but changing the wires and the pipes coming into the house and being routed around and under the house. It's that significant a change," says Paul Hill, a NASA flight director. "And it's all going to be done outside."
Then come the missions of 2007, during which the shuttle will drop off more basic- infrastructure components. To install them in their permanent locations, space-station crew members will use the station's robotic arm and conduct spacewalks to move existing elements in two high-stakes, slow-motion games of musical modules. At one point, they will have to disable and move the only connector, or node, capable of mating with the space shuttle – critical for resupply and crew exchanges, as well as construction.
If astronauts damage that connector, "the contingency scenarios get kind of ugly," Mr. Hill says. Between December's wiring and plumbing job and the station crew's segment shuffles, the next 12 months will see NASA undertake "the three most complicated things we're going to do in the entire construction of the space station."
Indeed, as the space station grows larger, it also gets brighter in the night sky. NASA has posted an interactive guide on its website (spaceflight.nasa.gov/realdata/sightings/index.html) so viewers can figure out when the space station might be visible to the naked eye.
Mission managers delayed Atlantis's return by a day because of bad weather at the landing site and an odd object orbiting in tandem with the shuttle. Ground controllers discovered the object while they were scanning Earth with a camera on the orbiter's robotic arm. Although its nature remains a mystery, NASA's best guess is that the tag-along was a small, thin plastic shim technicians use to maintain proper spacing when they install or replace heat-shielding tiles on the orbiter's underside. The shim was visible during an earlier inspection; it was missing when the crew inspected the orbiter after the object was spotted.
Three additional bits of cosmic flotsam eased into view outside the shuttle windows, but managers determined they were no threat, especially after a thorough inspection on Wednesday gave the orbiter's thermal protection system a clean bill of health. The system safeguards the orbiter and crew from the heat of reentry.
Indeed, an initial walk around the orbiter after it landed showed Atlantis to be the most ding-free orbiter in memory, officials said.
Atlantis's condition, as well as the excellent performance of the external fuel tank during Atlantis's rise into space, are prompting NASA officials to take a hard look at relaxing restrictions on night launches.
These were imposed for the first two flights following the Columbia disaster to ensure adequate lighting for cameras on the orbiter, boosters, and the fuel tank that monitor debris coming from the tank. The tank's positive report card could prompt officials to shelve efforts to redesign it further.
"We will look carefully at whether we need to change ice-frost ramps," Dr. Griffin said, referring to fixtures on the tanks that currently are targets for a makeover.