UPDATE ON SPACE SHUTTLE LAUNCH SET FOR THURSDAY NIGHT 12-7-2006

CAPE CANAVERAL - Before the space shuttle Discovery can embark on a mission to rewire the international space station's electrical system, NASA engineers have to resolve two late-breaking technical worries: a brief power surge and potential problems with a glue that helps seal rocket boosters.

Engineers will spend much of Wednesday trying to decide whether the two problems are minor or major. It's too early to tell if these will postpone Discovery's scheduled liftoff at 9:35 p.m. EST Thursday, said launch integration manager LeRoy Cain.

"I don't know enough about either one of the problems," Cain said in a Tuesday evening press conference.

The split-second power surge occurred early Tuesday when power was about to be switched from the shuttle's launch platform to Discovery itself. Early tests found that the shuttle's main engines, boosters and external fuel tank are OK after the power burst, but NASA was not saying the same about Discovery, Cain said.

Concern about booster-seal glue involves the adhesive that helps connect segments of the solid rocket boosters together.

Routine tests found that the adhesive used on some of the connection joints in the boosters might not be as strong as it should be, NASA spokeswoman June Malone said. But the adhesive is only of one many systems that keep hot gas from escaping and is not one of the main ones, she said.

"The adhesive does not produce the seals," Malone said. The seal mostly comes from the pressure of the segments themselves, she said.

Aside from those potential problems and a concern about worsening weather, NASA was marching toward its first nighttime launch in four years.

"We're on track and on target for Thursday," Cain said.

However, each time meteorologists updated their weather forecasts this week, the chance for clear enough skies for a launch dropped. As of Tuesday night, meteorologists gave NASA a 60 percent chance of good enough weather to launch — down from 70 percent earlier in the day and 80 percent on Monday.

A front that was supposed to push the clouds away slowed down, making forecasters worried that low-hanging clouds will violate NASA weather rules, said Lt. Kaleb Nordgren, shuttle weather officer.

If the clouds bog down Thursday's attempt, the weather gets only worse on Friday and Saturday. Because of projected high winds, forecasters give NASA only a 40 percent chance for those two days.

Weather will improve early next week. NASA has four launch opportunities over five days, if need be, to start the 12-day mission.