CAPE CANAVERAL, Fla. - Space shuttle Atlantis closed in for a weekend rendezvous with the international space station, a complicated job made even tougher by a failed navigation device.
One of Atlantis' two star trackers was deemed unusable Saturday, forcing commander Terrence Wilcutt and his co-pilot, Scott Altman, to add a couple of flip-flop maneuvers to their repertoire.
''It adds a little bit of complexity,'' said flight director Phil Engelauf.
The linkup was scheduled to take place 220 miles above the border between Russia and Kazakstan early Sunday.
Although still uninhabited, the space station has expanded since astronauts last visited in May.
The arrival of the Russian control module, Zvezda, 1 months ago nearly doubled the space station's size. A Russian supply ship carrying toilet components, oxygen generators and other gear quickly followed.
Atlantis' seven astronauts and cosmonauts will unload the supply ship as well as the shuttle later this week. They will install as much of the equipment as possible to ease the burden for the first permanent residents, who are due to move in at the beginning of November.
In preparation of Atlantis' arrival, flight controllers turned on the heaters inside the U.S. segment of the space station. They also were going to cleanse the air inside the much larger Russian section.
Following docking, the crew planned to duck into an outer space station compartment to take an air sample for analysis back on Earth. NASA wants to see how well the air filters inside the station work.
The five Americans and two Russians will not venture all the way into the space station until Tuesday. First, two of the crew will go out on a spacewalk Monday to string power and data cables between Zvezda and the other Russian module, Zarya.
The star-tracker failure, detected shortly after Friday's launch, meant extra work for the two shuttle pilots.
The plan called for Wilcutt and Altman to roll Atlantis once the shuttle was nine miles from the space station late Saturday, then flip it back into the proper position for the final approach.
Flight director Engelauf said the switch in position would allow the working star tracker, which points out toward the left cockpit window, to lock onto the space station.
The astronauts trained for such an event before the flight, Engelauf said. He could not recall a star tracker failing on the 98 previous shuttle missions.
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