CAPE CANAVERAL, Fla. - NASA has delayed Thursday's planned launch of space shuttle Atlantis on its STS-122 mission to the International Space Station. The next liftoff opportunity is Friday at 4:09 p.m. EST.

Shuttle program managers decided to postpone Atlantis' launch at 9:56 a.m. because of an issue with a fuel cut-off sensor system inside the external fuel tank. This is one of several systems that protect the shuttle's main engines by triggering their shut down if fuel runs unexpectedly low. During countdown activities Thursday morning, two sensors failed a routine prelaunch check. There are four engine cut-off, or ECO, sensors inside the liquid hydrogen section of the tank, and Launch Commit Criteria require three of the four sensor systems to be functioning properly.

The tank's liquid oxygen and liquid hydrogen will be drained from the tank, and preparations will begin for a possible launch attempt tomorrow. NASA's launch rules have a preplanned procedure that states in the case of ECO sensor system failure, engineers need to drain the tank and verify all the sensors are working as they go dry. This and other data will be discussed at a Mission Management Team Meeting at 2 p.m., when a decision will be made whether to attempt to launch on Friday. A news conference will follow that meeting at 4 p.m.

During Atlantis' 11-day mission, the crew will install and activate the European Space Agency's Columbus laboratory, which will provide scientists around the world the ability to conduct a variety of life, physical and materials science experiments.

Atlantis' crew consists of Commander Steve Frick, Pilot Alan Poindexter, mission specialists Leland Melvin, Rex Walheim, Stanley Love and European Space Agency astronauts Hans Schlegel, from Germany, and Leopold Eyharts, from France.

For the latest information about the STS-122 mission and its crew and more information about engine cut-off sensors, visit:http://www.nasa.gov/shuttle

Source http://www.nasa.gov/home/hqnews/2007/dec/HQ_07266_Atlantis_Scrub_Release.htm...