Three of four sensors must work to launch Feb. 7

After a two-month launch delay to troubleshoot and replace a suspect connector, NASA's Program Requirements Control Board today recommended launching on Feb. 7, even if only three of four low-fuel sensors give the proper readings during fueling.

This drops the four of four standard implemented for Atlantis' last launch attempt at the recommendation of the astronaut office.

After a scrubbed launch attempt on Dec. 6, NASA required all four low-fuel sensors to work properly for the second launch attempt three days later. This requirement forced the second launch attempt to be scrubbed on Dec. 9, when one sensor gave suspect readings.

"That wasn't a permanent change," NASA spokesman Candrea Thomas said. "That was just for that launch attempt."

The recommendation must be approved Friday by a program level Flight Readiness Review, led by shuttle program manager Wayne Hale, and by an executive Flight Readiness Review, led on Jan. 30 by Bill Gerstenmaier, associate administrator for space operations.

During a two-month delay of the Atlantis mission, NASA has replaced a feed-through connector in the external tank. The connector is suspected of causing current interruptions when cooled to 423 degrees below zero by liquid Hydrogen.

Cryogenic tests of the faulty connector, as well as of a new connector, indicate NASA's hypothesis is correct.

The sensors would shut down the engines before they ran out of fuel. NASA's four of four working criteria, was adopted after the Challenger accident. The standard was lowered to three of four working after sensor reading problems during the Return to Flight following the Columbia accident.

Also at today's meeting, officials recommended a launch date for the mission after Atlantis that will make up time, returning NASA to a schedule to complete 13 shuttle missions by 2010, when the shuttle program is to end.

Endeavour is scheduled to launch March 11 at 2:31 a.m., carrying a Japanese laboratory to the International Space Station.

The new shuttle launch schedule:

Atlantis STS-122 on Feb. 7: Two-month delay.

Endeavour STS-123 on March 11: One-month delay.

Discovery STS-124 on April 24: Restores the original schedule.

Atlantis STS-125 on Aug. 7: Hubble repair, possibly Atlantis' last mission.

IMAGE NOTE: Click to enlarge the NASA photo of Jim Davis, a NASA quality inspector, examining an internal connector in the engine cutoff sensor system of shuttle Atlantis' external tank. Problems with an feed-through connector that hooks up to the internal connector forced NASA to scrub consecutive launch attempts in December. The faulty feed-through connector has been replaced and NASA is aiming to launch Atlantis and the European Columbus laboratory on Feb. 7. Photo credit: NASA/George Shelton.