HOUSTON - The stage is set for a space shuttle mission that will resume construction of the international space station in a big way - a mission that also ranks among NASA's longest-running buildups to launch.
NASA officials aren't due to give formal approval to the shuttle Atlantis' timetable until next Wednesday, but during a series of briefings here at Johnson Space Center on Friday, they said nothing was standing in the way of a launch as early as Aug. 27 on an 11-day mission.
"We feel that we are now prepared to go back into an assembly operations mode," after a hiatus of three and a half years, NASA shuttle program manager Wayne Hale told reporters.
That gap was forced on NASA by the loss of the shuttle Columbia and its crew in 2003. Two test missions were flown by the shuttle Discovery last summer and last month, giving the space agency the confidence to go ahead with construction once more.
The main focus of this mission is to install a power-generating structure that would eventually give the station a 20-kilowatt power boost — enough to power six houses, said Mike Suffredini, NASA's space station program manager.
Weighing in at 17.5 tons, the P3/P4 truss segment ranks among the "heaviest elements that we will fly to the ISS," Suffredini said.
The shuttle's robotic arm will pull the structure out of Atlantis' cargo bay and pass it over to the station's robotic arm to begin the installation, representing what Canadian astronaut Steve MacLean called "the great Canadian handshake." MacLean will be the first Canadian to operate both of the Canadian-built arms, and will also participate in one of the three spacewalks required to hook up the truss structure.
Also on Atlantis' crew are commander Brent Jett, who presided over a similar truss installation during a trip to the station in 2000; pilot Chris Ferguson; and spacewalkers Joe Tanner, Dan Burbank and Heide Stefanyshyn-Piper. This will be the first space mission for Ferguson and Stefanyshyn-Piper.
During this mission, the structure's 240-foot (73-meter) solar arrays are to be unfolded, either by remote control or manually if necessary. The arrays are designed to rotate to track the sun as the station orbits, to generate maximum power. But it will take additional work during future shuttle missions to reposition the arrays and get the power actually flowing.
The clearances for installing the truss are as little as an inch (2.54 centimeters), and pairs of spacewalkers will sometimes have to split up to get everything done on time. Such missions will be the norm over the next four years, leading to the space station's scheduled completion in 2010, said Phil Engelauf, chief of NASA's flight director office.
"These are extremely intense, extremely choreographed missions," he said.
The launch schedule for Atlantis is also tightly choreographed.
A Russian Soyuz craft will be waiting in the wings, prepared to send the station two fresh crew members and a Japanese space passenger who's paying a multimillion-dollar fare. If Atlantis can be launched by Sept. 3, then the Soyuz can launch Sept. 14, after the shuttle leaves the station. If the shuttle is launched in the Sept. 4-7 period, the Soyuz's liftoff would be delayed until Sept. 18, Suffredini said. And if the shuttle can't be launched by Sept. 7, its launch window would close and the Soyuz would take off as planned on Sept. 14.
Although Hale said the focus of the shuttle program was shifting from safety tests to space station assembly, he emphasized that Atlantis' flight — indeed, every shuttle flight from now until the fleet's retirement in 2010 — would be considered experimental. The shuttle's ascent will be closely monitored, just as it was during Discovery's test flights, and three rounds of on-orbit inspections will be carried out before, during and after Atlantis' rendezvous with the space station.
Jett, the STS-115 mission's commander, noted that the flight will alternate safety-testing tasks with assembly tasks. "It's almost like you can pick and choose the days of our mission and say, 'OK, this is really a legacy of the test objectives from the previous mission, and then the other days we're really focused on the operation and assembly of the station," he told MSNBC.com.
Atlantis' crew members have been training for this mission for four and a half years, since before the Columbia tragedy — leading Ferguson to joke that he and his crewmates have been working on "a graduate degree in STS-115." But the astronauts said they've gotten along amazingly well over all that time.
"Four and a half years together, and we've never had an argument," Tanner said. "Wouldn't it be nice to have a marriage that peaceful?"