Discovery countdown under way

Discovery on the launch pad at Kennedy Space Center on Monday

KENNEDY SPACE CENTER, Florida (CNN) -- The countdown began Monday for Thursday's scheduled launch of the space shuttle Discovery on a mission to deliver a relief crew to space station Alpha.

Discovery's crew, along with the first replacement crew for Alpha, arrived at Kennedy Space Center late Sunday night to begin final preparations for their upcoming mission.

The countdown clock started ticking at 10 a.m. EST. Launch is scheduled for 6:42 a.m. EST on Thursday.

NASA mission managers said on Monday that Discovery is in great shape, but the weather on Thursday may be a problem.

"We're somewhat concerned about violating the cold temperature launch-commit criteria for this launch," said Ed Priselac, the shuttle's weather officer.

Priselac estimated temperatures would be in the mid-40's at launch time.

"We're still better than 50-50, looking for a 30 percent chance that cold temperatures could keep us on the ground," Priselac said.

WEATHER FORECAST Cape Canaveral, Florida   MISSION GUIDE STS-102   RESOURCES Space Shuttle Central   MESSAGE BOARD Human spaceflight

NASA is worried that cold weather could cause ice to build up on the shuttle's external fuel tank.

"That's our primary concern that we have is with icing that may build up on the tank," said Jeff Spaulding, NASA test director.

The main objective of the mission is to deliver Alpha's three person replacement crew and to carry up an Italian-built module called Leonardo. The module is loaded with experiments for the newly installed Destiny science lab.

The crew arrived at KSC around 11 p.m. EST on Sunday. Later, Commander James Wetherbee and pilot James Kelly practiced landings in the shuttle training jets.

Discovery is scheduled to land in the dark, around 2 a.m. EST, on March 20.

The shuttle crew also includes mission specialists Andrew Thomas and Paul Richards and the second crew for space station Alpha: Russian commander Yury Usachev and flight engineers James Voss and Susan Helms, both U.S. astronauts.

"It's been a long time getting here," said Helms after arriving at KSC. "We'll be up there a long time, several months. We won't see you until the landing probably this fall."

Helms will be the first female crew member of space station Alpha. She, along with Usachev and Voss, is scheduled to remain on Alpha for four months.

After dropping off Usachev, Voss and Helms at the space station, Discovery will bring home the first station crew, U.S. commander Bill Shepherd, pilot Yuri Gidzenko and flight engineer Sergei Krikalev. The three crewmembers have spent more than four months in orbit aboard Alpha.

The space station command officially changes hands when Discovery undocks from the station.

Also on Monday, the space shuttle Atlantis arrived back at Kennedy Space Center. Atlantis was forced to land at Edwards Air Force Base in California after last month's mission because of bad weather in Florida. The shuttle was transported to Florida on a jumbo carrier jet.

The shuttle Columbia arrived a few hours later on another jumbo jet. Columbia had been in California for 17 months undergoing modifications and repairs.

NASA said it marked the first time two shuttles had arrived at KSC on the same day on the back of carrier jets.

Discovery a true shuttle on next mission
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March 2, 2001
Cargo ship makes delivery to space station
February 28, 2001
Shuttle touches down in Mojave Desert
February 20, 2001

NASA
International Space Station - Science Operation News

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