Technicians at the Kennedy Space Center are spending the day loading experiment samples, subjects and hardware into a Spacehab module in the shuttle Columbia's cargo bay in preparation for launch Thursday on a 16-day microgravity research mission. With no technical problems at pad 39A, forecasters continue to predict a 95 percent chance of good weather during Columbia's launch window. The odds drop to 40 percent "go" on Friday.

NASA managers, meanwhile, plan to meet this afternoon for a standard launch-minus-two-day review of Columbia's processing and readiness for flight. The only open issue on the table is the results of an investigation into the health of large bearings in the shuttle's propellant lines that allow the pipes to flex slightly under launch vibrations.

A crack was found in one of the shuttle Discovery's 16 bearings last month and while no other cracks have been found to date, Columbia's bearings cannot be inspected at the pad. Engineers have been studying the issue to determine whether a bearing failure in flight could produce debris that, in turn, could get sucked into a main engine with possibly catastrophic results.

This issue was all but put to bed during an engineering teleconference Sunday. Barring some unexpected result from a few final tests, NASA's mission management team is expected to formally resolve the matter today and clear Columbia for takeoff.

Overnight, engineers successfully filled on-board tanks with liquid oxygen and hydrogen to power Columbia's three electricity producing fuel cells for the duration of the 16-day mission.

At pad 39A today, technicians are working to install last-minute experiment samples and subjects, including high-tech cages for 13 rats, into Columbia's Spacehab research module. Because the shuttle is vertical at the pad, a technician must be lowered down a tunnel between the shuttle's crew cabin and the Spacehab module to make the necessary installations.

"All told, it's about 20 hours of very demanding work," said Jack Keifenheim, a payloads manager at the Kennedy Space Center. "It's critical that we stay on schedule because following that, we get into our middeck late stowage and everything has to go like clockwork."

He was referring to installation Wednesday of final experiments, samples and critters in lockers on the shuttle's lower deck. Despite the tricky, last-minute nature of the work, no problems are expected.

"In summary, the launch countdown is continuing right on track for Thursday, the flight and the ground hardware and systems are in great shape," said NASA test conductor Pete Nickolenko. "The launch team and the many mission support teams around the world are focused and ready to support launch on Thursday."

Liftoff is targeted for sometime between 10 a.m. and 2 p.m. The exact launch time will be announced Wednesday.