CAPE CANAVERAL, Fla. -- Faced with a forecast for dangerously cold weather, NASA on Wednesday delayed the planned launch Thursday of shuttle Columbia on a Hubble Space Telescope repair mission for 24 hours.
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With a crew of seven astronauts aboard, the shuttle now is scheduled to set sail for the $3 billion telescope during a 62-minute launch window that will open at 6:22 a.m. EST (1122 GMT) Friday.
An initial launch attempt had been slated for Thursday, but senior managers decided to postpone the flight because the temperatures at the assigned launch time -- 6:48 a.m. EST (1148 GMT) -- are expected to dip to 38 degrees Fahrenheit.
"The forecast is right at the redline for unacceptable temperatures," said Bruce Buckingham, a spokesman for NASA's Kennedy Space Center. "So we've decided not even to make an attempt Thursday."
Strict NASA safety rules call for a launch attempt to be called off if temperatures are too cold and wind speeds are not high enough to keep ice from forming on the shuttle's 15-story external tank.The prime concern is that chunks of ice could break free from the tank at liftoff, potentially damaging the orbiter's fragile thermal tiles after liftoff. The tiles are critical to protecting the ship and its crew from the intense heat the orbiter is exposed to during atmospheric reentry.
The temperatures Friday are expected to be much warmer -- 48 degrees Fahrenheit at launch time, Buckingham said.
"So we'll just basically stand down for 24 hours and then pick up the countdown for a launch attempt Friday," he said.
Mission managers, meanwhile, still are analyzing a potential problem with wheel bearings within the shuttle's main landing gear.
The suspect bearings were not put through the proper heat-treatment process when they were manufactured, so engineers want to make certain that the main landing gear wheels will in fact work properly when Columbia returns to Earth.
The issue, however, had no bearing on the launch delay.
"This was strictly a decision based on the weather and not on any other mechanical issue such as the bearings," Buckingham said.
A decision on whether to replace the bearings on Columbia's main landing gear will be made before NASA begins fueling the shuttle Thursday night for a launch attempt Friday. Replacing the suspect bearings would force NASA to return Columbia to a shuttle hangar, a move that would delay the shuttle mission several weeks.
The mission will be NASA's fourth servicing trip to the Hubble telescope, one that will involve five difficult spacewalks on consecutive days.
Columbia's seven-member crew aims to outfit the observatory with an advance planetary camera, revive a dormant infrared science instrument, install a fresh set of solar wings, replace a faulty pointing control device and overhaul Hubble's electrical system.
A launch Friday would lead to a March 12 landing here at NASA's coastal Florida spaceport.
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