"We've done everything we need to do" for the safety of shuttle flight, and "we are in good shape," he told a news conference after a meeting of NASA officials, one day before Discovery's liftoff, which is scheduled for 3:51 p.m. EDT (1951 GMT) Wednesday.  (Photo: Xinhua/AFP)

CAPE CANAVAREL, Florida, the United States, July 14 (Xinhuanet) --NASA engineerings have failed to tackle the technical problem that suspended the planned Wednesday launch of Discovery, and the extremely optimistic prospect is for the next launch try to occur on Sunday, said NASA on Thursday.

    A Sunday launch is a "really optimistic good-luck scenario", said Wayne Hale, NASA's shuttle program deputy manager. It is more likely the next launch attempt would come beyond Sunday.

    However, Hale said "I'm not ready to give up on a July window. We still have several days ahead of us." The July window runs until the end of the month. The next launch window is in September.

    Hale said NASA has now 12 engineering teams around the country at work to check what caused the failure of a fuel sensor to work properly during the Wednesday pre-launch test and NASA will have to check every aspect of the problem.

    The faulty sensor, one of the liquid hydrogen fuel four sensorsin stalled at the bottom of the shuttle external fuel tank, is expected to indicate the low level of hydrogen fuel in the tank and warn when fuel tank is dry.

    But in the pre-launch check Wednesday, it was found to be not working properly, leading to the call-off of launch more than two hours prior to liftoff. A similar problem occurred in the April tanking test with the cause remaining unknown. But all sensors worked properly during the second tanking test in May.

    The nightmare is that as engineers cannot find the cause of the problem, they cannot find a solution.

    The launch of Discovery is on the first shuttle flight mission of NASA since the 2003 Colombia disaster, which killed all seven astronauts on board. Enditem