NASA on Sunday delayed the launch of space shuttle Atlantis until January after a gauge in the fuel tank failed for the second time in four days.
With only a few days remaining in the launch window for the shuttle's mission to the international space station, senior managers decided to stand down until next month in hopes of better understanding the perplexing and persistent fuel gauge problem.
"We're determined to get to the bottom of this," said LeRoy Cain, chairman of the mission management team.
Whether Atlantis can fly as early as Jan. 2 "is all going to depend on what we find out," he said.
The trouble with the fuel gauge resurfaced just before sunrise Sunday, about an hour after the launch team began filling Atlantis' big external tank for an afternoon liftoff.
Shuttle managers had said they would halt the countdown and call everything off if any of the four hydrogen fuel gauges acted up. Three failed during Thursday's launch attempt; no one knows why.
Launch director Doug Lyons said Sunday's failure was similar to what happened before, except only one gauge malfunctioned this time.
"We would rather have launched today, obviously," Cain said. "This was going to be in the very least a good tanking test for us, and that's what it's turned out to be."
NASA quickly established an engineering team to come up with ideas on how to pinpoint and fix the problem, which has bedeviled NASA off and on for the past two years. The engineers will report back to Cain and other managers on Tuesday.
Most inspections and repairs could be carried out at the launch pad. If the shuttle has to be returned to its hangar for more invasive work, there will be no hope of launching in early January, Cain said.
NASA had until Thursday to launch Atlantis with the European Space Agency's space station laboratory, Columbus. After that, unfavorable sun angles and computer concerns would make it impossible for the shuttle to fly to the international space station until next month.
Despite objections from some engineers, NASA tightened up its launch rules for Sunday's attempt in hopes of getting Atlantis off the ground by the week's end.
Not only did all four of Atlantis' fuel gauges have to work on Sunday — until now, only three good gauges were required — but a new instrumentation system for monitoring these gauges also had to check out. NASA also shrank its launch window from five minutes to a single minute for added safety.
The troublesome gauges, called engine cutoff sensors, are part of a backup system to prevent the shuttle's main engines from shutting down too late and running without fuel, a potentially catastrophic situation. They have been a source of sporadic trouble ever since flights resumed in 2005 following the Columbia tragedy.
Two groups of NASA engineers recommended that the flight be postponed and the fuel gauge system tested, to figure out what might be going on. But they did not oppose a Sunday launch attempt when it came time for the final vote.
Shuttle commander Stephen Frick was deeply involved with the decisions that were made, officials said.
Frick and his six crewmates departed for their home base in Houston late Sunday afternoon. "We hope everyone gets some well-deserved rest and we will be back to try again when the vehicle is ready to fly," the astronauts said in a prepared statement.
It was another disappointing delay for the European Space Agency, which has been waiting for years for its $2 billion Columbus lab to fly. NASA space station design problems in the 1980s and early 1990s slowed everything down, then Russian troubles and, most recently, the 2003 Columbia tragedy stalled the project.
"Another few weeks isn't going to make any difference," said Alan Thirkettle, the European space station program manager. "We want to fly, but we want to fly safe."
NASA officials said they expect little ripple effect on space station construction.