Shuttle Launch Date Slips as NASA Tackles Sensor Fix

NASA'slaunch of the space shuttle Atlantis has slipped to late January, with a pushto early February likely, as engineers work to replace a faulty fuel tankconnector, a top official said Thursday.

JohnShannon, NASA's deputy shuttle program manager, said Atlantis will not flyuntil Jan. 24 at the earliest, a two-week slip from an earlierJan. 10 target, to allow tests and modifications of a vital fuel tankconnector.

"Everythinghas to go exactly right for us to make the 24th," Shannon told reporters.

More likelylaunch targets are Feb. 2 or Feb. 7, which allows time for extra tests but nomajor unexpected surprises, Shannon said.

Atlantis'planned 11-day mission to deliver a new Europeanlaboratory to the International Space Station (ISS) has been delayedsince early December, when vital fuel gauge-like sensors failed standardcountdown checks. Known as engine cutoff sensors, the fuel gauges serve as abackup system to shutdown an orbiter's three main engines before its fuelsupply runs out.

NASAtracked the glitch to a suspectelectrical connector near the bottom of Atlantis' 15-story external tank,where sporadic open circuits may form as the tank is filled with its super-coldliquid hydrogen propellant.

Thethree-part connector consists of an interior electrical socket, a glass-and-metalpin bridge and an exterior electrical socket that work together to transmit signalsfrom four liquid hydrogen fuel gauges to a computer aboard Atlantis.

Engineershave already removed exterior portions of the electrical connector and willreplace it next week with a modified version with wires soldered directly totheir corresponding pins to avoid open circuits, NASA said.

"It'sfairly simple," said Shannon. "It's a fairly elegant change and wefeel very confident that, if the problem is where we think it is?that this willsolve that."

NASArequires at least a five-week breather between shuttle launches, which pushesthe planned Feb. 14 launch of the Endeavour orbiter and the first part of Japan's massive Kibolaboratory beyond its initial target, he added.

The spaceagency also must not conflict with the planned ISS arrival of the unmannedRussian Progress 28 cargo ship, which is currently slated to launch on Feb. 7.

"The hardconstraint today is not to have a shuttle docked while we're trying to dock aProgress," said Mike Suffredini, NASA's ISS program manager.

Suffrediniadded that ISS managers are also discussing when to add an extra spacewalk tothe chore list of the space station's Expedition 16 crew to replace a solar wingmotor.

Commanded byveteran spaceflyer Stephen Frick, Atlantis' seven astronauts expect to installthe European Space Agency's Columbus laboratory and stage at least threespacewalks slated for their shuttle mission.

"Theydid get the holidays off. I think that was a good thing," Shannon said ofthe shuttle astronauts. "They're, from all I can tell, very excited andready to go whenever the shuttle is."

• Top 10 Spaceflight Stories of 2007
• SPACE.com Video Interplayer: NASA's STS-122: Columbus Sets Sail for ISS
• VIDEO: ISS Commander Peggy Whitson Takes Charge