CAPE VANAVERAL, FLORIDA, the United States, July 24 (Xinhuanet) -- The US National Aeronautics and Space Administration (NASA) said Sunday it would launch Discovery Tuesday if the same fuel sensor glitch reoccurs.

   

Wayne Hale, Space Shuttle deputy program manager, shows a fuel sensor to journalists at Kennedy Space Center in Cape Canaveral of Florida, US, July 24, 2005. NASA will attempt to launch space shuttle Discovery on July 26 on the first shuttle mission since the 2003 Columbia disaster. The decision was made after engineers found the most likely causes of the fuel sensor problem that delayed the launch of Discovery on July 13. (Xinhua Photo)

 "If the problem recurs and under very closely defined circumstances in sensor number 2 or sensor number 4, then we will do some more tests and if we are comfortable that we have a good understanding of the cause then we can go fly," space shuttle program deputy manager Wayne Hale told a news conference Sunday afternoon.

    NASA called off the first launch attempt on July 13 in the last minute as sensor number 2 malfunctioned during the pre-launch test. And the US space agency has now switched the wiring between sensor number 2 and sensor number 4.

    "If things go our way, we'll see our first space shuttle launch in two and a half years," said Hale. The 12-day mission of Discovery will be the first shuttle flight since the Columbia disaster in February 2003, which killed all seven astronauts aboard.

    Hale stressed that if any of the other low fuel level sensors does not work properly, NASA will halt the second launch try.

    The shuttle external tank has four fuel sensors in it to protect the shuttle's main engines and trigger their shutdown in the event that the liquid hydrogen fuel would run unexpectedly low.

    Two fuel sensors that work well can be enough to protect the shuttle's main engines. However, as a NASA rule, a shuttle launch requires all the four working properly.

    Despite tremendous efforts, NASA has failed to explain what caused the sensor problem. One of the possibilities is that modifications in design made to the external tank to minimize the debris risk lead to the sensor malfunction.

    NASA hopes that it can find out the root cause of the sensor problem during the pre-launch testing Tuesday while the external tank is being filled.

    The possibility that an unfavorable weather blocks the Tuesday launch try is about 40 percent. Enditem