ECO Sensor Glitch Postpones Atlantis Once Again

ANN REALTIME UPDATE 12.06.07 2120 EST: NASA now says the launch of the space shuttle Atlantis will take place no earlier than Saturday, due to a stubborn glitch with a fuel cutoff sensor system inside the shuttle's external fuel tank.

The fuel cutoff sensor system is one of several that protect the shuttle's main engines by triggering their shut down if fuel runs unexpectedly low. Launch Commit Criteria require that three of the four sensor systems function properly before liftoff.

Space Shuttle Program managers will hold a Mission Management Team meeting Friday at 2 pm to discuss the issue and determine the steps necessary to start a new launch countdown.

For the moment, there is no scheduled launch time for Atlantis... but if NASA can fix the sensor problem, launch will likely occur at 1543 EST Saturday.

Original Report

"At least the issue wasn't weather." That's how one CNN commentator summed up NASA's postponement of the launch of the space shuttle Atlantis Thursday, due to two malfunctioning sensors on the shuttle's external fuel tank.

There are four such engine cutoff (ECO) sensors, which measure liquid hydrogen levels in the external tank to determine when the shuttle's main engines should cutoff. NASA protocols require at least three of those sensors to be operational to launch the shuttle.

NASA engineers discovered the problem when they commanded the sensors to indicate the tank was empty. The two problem sensors continued to show the tank was full, NASA spokesman Paul Foerman told The Associated Press.

A similar problem postponed the September 2006 launch of Atlantis, as ANN reported. The delay put an end to NASA's streak of three on-time shuttle launches this year.

Another attempt is scheduled for Friday, providing engineers are able to determine the nature of the sensor problem.

STS-122 will deliver the European Space Agency's Columbus scientific laboratory to the International Space Station.

ESA has worked on Columbus for over 22 years... making the launch delay a nerve-wracking stutter for those involved in what ESA station program manager Alan Thirkettle called "our cornerstone, our baby, our module, our laboratory."

On Wednesday, NASA Administrator Michael Griffin admitted the agency fell behind on design and development of the International Space Station, though he said the agency has executed the plan well overall.

"We the United States, as the senior partner in the space station coalition, did not plan it well," Griffin said on the eve of Columbus' launch. "It has taken far too long and I'll just leave it at that."

FMI: www.spaceflight.nasa.gov