The paper chase and fine-tuning has begun as engineers finish up the final flight preparations for the first shuttle launch in nearly three years.

The orbiter Discovery stood ready as the sun rose over the central Florida coast Wednesday, the day before the launch."Basically we're on schedule," Frank Merlino, NASA test director at the Kennedy Space Center, said at a Wednesday morning news conference.

The countdown has started, and the revelers were lining the coastal areas around the Kennedy Space Center while engineers prepared the orbiter for flight. The launch, weather and technology permitting, is set for 7:59 a.m. MDT Thursday.

"Today, the winds look like they'd be acceptable locally, and tomorrow they expect the same. But the clouds are problematic," Merlino said.

Two problems have developed recently. NASA officials said a surface abrasion was discovered in the protective covering of one of the shuttle's front thrusters. And there's a possibility a flaw was found in the sealing ring of a communications satellite's propulsion system.

But that problem with the O-ring seal, which is not made by the same Utah company that manufactures shuttle booster rocket O-rings, was found on a piece of hardware not on the launch pad.

"The testing is going to show us that we've looked at the worst-case kind of thing," said Parker Counts, manager of NASA's upper stage program. "We're trying to duplicate the failures we saw with those in a test setup and run a pressure test to see even if we had a similar type cut or discrepancy, we could seal those units."

Officials with the National Aeronautics and Space Administration said neither of those problems was serious enough to postpone the launch.

The one crucial element that could prevent the launch, aside from a technological problem that officials seem to have discounted, is weather.