NASA began installing a new connector in Atlantis' fuel tank Friday in hopes of launching the space shuttle in early February, two months late.
The space agency is aiming for a Feb. 7 launch of the mission to deliver Europe's long-awaited lab, Columbus, to the international space station.
Atlantis was grounded after fuel gauges in its external tank failed late in the countdown Dec. 6 and again three days later.
A fueling test right before Christmas traced the problem to a faulty connector that passes through the bottom wall of the fuel tank and links wiring from the gauges to the shuttle.
That connector is undergoing tests at super-cold temperatures at Marshall Space Flight Center in Huntsville, Ala.
Another connector — with freshly soldered pins and other modifications — is being installed in the tank at the launch pad.
On Friday, technicians spliced wires for the hookup, said NASA spokesman George Diller. The new connector will go in Saturday, with follow-up work and testing through the weekend, he said.
NASA had hoped to launch Atlantis in January, but needed more time to complete the connector work. Shuttle managers also had to work around a Russian cargo ship's planned delivery.
The unmanned cargo ship had been scheduled for a Feb. 7 launch, but the Russians were expected to move it up a few days to accommodate Atlantis.
NASA has been plagued by fuel gauge trouble for nearly three years — ever since shuttle flights resumed following the 2003 Columbia tragedy — and is hoping the connector repairs will solve the problem once and for all.
The fuel gauges are part of a critical safety system to prevent the main engines from running on an empty tank, a potentially catastrophic situation.
Because of Atlantis' delay, the subsequent shuttle flight to the space station — carrying up the first piece of a massive Japanese lab — will not take place until mid-March. That's a month later than planned.
NASA hopes to be back on track by late April, with an on-time launch of Discovery with the second part of Japan's lab.
The space agency is under presidential orders to complete the space station and retire the three remaining shuttles by 2010.