With engineers in Florida "baby sitting" the shuttle Atlantis, NASA workers at the Johnson Space Center in Houston have completed work to power down sensitive mission control computer systems in preparation for the approach of Hurricane Lili.

Control of the international space station's U.S. segment has been transferred to a small NASA contingent at the Russian mission control center near Moscow. Computer systems at the Johnson Space Center that normally support station and shuttle operations have been shut down, a complex procedure that has never been done before.

In the meantime, launch of the shuttle Atlantis, originally scheduled for today, is on hold until Monday at the earliest. Many of the JSC workers stationed in Florida for the STS-112 launch campaign have flown back to Texas. Atlantis' crew, however, elected to remain in Florida with their families.

"As you can imagine, last night there was a flurry of activity at JSC as they continued their hurricane preparations to deal with the approach of Hurricane Lili," astronaut James Halsell, chairman of NASA's mission management team, told reporters today.

"They continue to believe, with a high level of confidence, that it will make a turn to the north away from the area and yet that turn will not become visible until later on this evening, maybe not until the wee hours of the morning. So as a result, JSC has to make the appropriate preparations for both the safety of their people and their resources to allow for an evacuation if that becomes necessary."

As a result, Halsell's mission management team agreed to delay Atlantis' launch to no earlier than Monday. That will give JSC workers time to prepare for and ride out whatever severe weather blows through and then to power up now-dormant computer systems. Those systems then will have to be checked out to make sure they are properly integrated. Flight controllers also plan to conduct limited simulations to confirm the computer systems are ready to support launch.

"The international space station component of the control center handed off control successfully last night to the support group at the mission control center in Moscow and then powered down the ISS mission control center element there in Houston," Halsell said. "In parallel with that, the shuttle mission control center, which had been fully prepped and the configuration frozen to support the shuttle launch, they also had to power down in preparation for a minimal manning circumstance.

"It will take some time after the hurricane makes landfall and the Johnson Space Center is able to reconstitute their personnel," he said. "It will take some time to for them to go through the procedures required to bring the power back up, to bring the systems back on line, to re-establish the network and then to go through a series of revalidations, retesting, to ensure they're absolutely, 100 percent ready to safely support. ... So that's how we ended up with Monday as a launch date."

Assuming engineers begin re-activating their computer systems Thursday as currently planned, control of the U.S. segment of the international space station should be transferred back to JSC sometime Friday, officials said.

The 11 a.m. forecast advisory from the National Hurricane Center in Miami says Lili, moving toward the northwest at 15 mph, has become a "major hurricane" with maximum sustained winds near 120 mph and gusts even higher.

"This makes Lili a dangerous Category 3 hurricane on the Saffir-Simpson hurricane scale," the advisory said. "Some additional strengthening is possible during the next 24 hours."

A storm surge of eight to 12 feet above normal is likely near the point where the eye of the storm makes landfall and six to eight inches of rain can be expected along the hurricane's track.

National Hurricane Center computer models are "tightly clustered" and show a narrow range of landfalls along the Louisiana coast centered on the region just south of New Iberia. Hurricane warnings extend from the mouth of the Mississippi River to just east of Galveston Bay, Texas, where the Johnson Space Center is located.

Asked if he was frustrated with this week's launch delay, Halsell said "I guess that's the nature of the business and the longer I'm in it, the more I get used to it."

"This is certainly a unique issue," he said. "To my knowledge, I don't know that the program has had to deal with a hurricane threatening JSC and the mission control center at the time we're trying to launch a shuttle here."

Shuttle launch director Michael Leinbach agreed, saying "If you can't accept a few curves in this business, then you don't belong here. Yeah, we would have liked to launch this afternoon or tomorrow. But we'll get there Monday and that'll be fine."

Leinbach said Atlantis' countdown will remain in a "hold" at the T-minus 11-hour mark. Late tonight, engineers will drain liquid oxygen and liquid hydrogen from the shuttle that power the ship's electricity producing fuel cells. Those tanks will be refilled Saturday, providing up to five launch opportunities. The shuttle's communications systems will be activated Sunday to set the stage for a Monday liftoff.

NASA's mission management team will meet again Sunday afternoon to assess launch preparations. A final news briefing is planned for 3:30 p.m. At that point, NASA will announce Atlantis' official launch time and release a detailed mission timeline. Until then, the previously announced 2 p.m.-to-6 p.m.launch window remains in effect.