NASA has approved a hydrogen fuel "tanking test" with the space shuttle Atlantis external tank on the launch pad no earlier than Dec. 18 to help solve engine cutoff (ECO) sensor problems that have grounded the next International Space Station assembly mission until early January (DAILY, Dec. 10).

The recommendations were presented at a regularly scheduled shuttle Program Requirements Review Board meeting at the Kennedy Space Center Dec. 11. Laboratory and bench testing of flight hardware unrelated to the upcoming mission also will be done to further explore ECO circuit vulnerabilities.

Tests with Atlantis still at Pad 39A will include use of a Time-Domain Reflectometer (TDR) pulse generator spiced into the ECO-sensor electronics. The device will inject electrical pulses into the circuit to help determine specifically where an impedance abnormality may lie along the about 100 feet of wiring involved with the ECO system. If a fault is found, how to fix it will be another problem altogether.

The Atlantis launch remains scheduled for no earlier than Jan. 2, but will not occur that soon because of the tests and holiday time off for Kennedy employees. From the standpoint of ECO-sensor safety philosophy, NASA is not planning to fly another shuttle mission until the problem is solved with Atlantis, according to Wayne Hale, the shuttle program manager.

This means the agency will not move the Atlantis launch with Europe's Columbus laboratory out of sequence and advance the launch of the shuttle Endeavour with the logistics module for Japan's Kibo laboratory, now set for Feb. 14, Hale said.