Space Shuttle Discovery may take the place of Space Shuttle Endeavour in performing standby life-guard duty when Space Shuttle Atlantis blasts off to refurbish the Hubble Space Telescope.

Atlantis was to launch next week, on Oct. 14, but the Hubble developed a system glitch, so Atlantis won’t fly on the STS-125 Mission until perhaps February, so the shuttle can carry aloft a replacement part for the ailing Hubble component.

Most shuttle flights go to the International Space Station, and that means that if a shuttle develops a major problem, its crew can use the space station as a life raft.

But Atlantis, which was rolled out to Launch Pad 39A, is going to the Hubble, which can’t provide that shelter.

That’s why Endeavour has been poised on Launch Pad 39B at Kennedy Space Center, to ride to the rescue if Atlantis should encounter trouble.

But now that Atlantis will be delayed by months in starting its Hubble refurbishment mission, the only trip Atlantis is taking this month is a 1 mph journey back to the Vehicle Assembly Building.

That means Endeavour moves Oct 25 from Pad 39B to 39A, for a launch on the STS-126 Mission to the space station, delivering a Multi-Purpose Logistics Module that will aid a move to double the station crew to six, from the current three.

Endeavour is to blast off in a window opening Nov. 14.

Once Endeavour departs, a shuttle will have to be assigned to perform the standby emergency life-guard duty when Atlantis finally does lift off, likely in February.

Since Space Shuttle Discovery is set to begin its STS-119 Mission to the space station on Feb. 12, it first could perform the life-guard duty, if Atlantis is set to head to Hubble early in February.

Otherwise, Endeavour might yet perform that task, if it is turned around in time after its STS-126 Mission.

In that mission, one Endeavour crew member, Sandra Magnus, will remain on the station for a long-duration stay after Endeavour undocks and heads back to Earth. She will take the place of current station resident crewman Greg Chamitoff.

Working inside the gigantic swimming pool at NASA’s Neutral Buoyancy Lab at Johnson Space Center, astronauts Steve Bowen and Shane Kimbrough are rehearsing the fourth spacewalk for the mission.

Technicians at Kennedy will remove the Hubble Space Telescope servicing hardware from the Atlantis cargo bay and place it inside its protective canister next Monday for transfer to the Payload Hazardous Servicing Facility.

Delays Occur As Deadline Looms

This latest delay comes as NASA moves steadily closer to the October 2010 deadline when President Bush has said the space shuttle fleet must retire.

Shuttles are the only vehicles with the size and brawn to hoist huge structural components into orbit to complete construction of the space station.

NASA officials have said, repeatedly, that they can finish building the space station and complete the manifest of shuttle missions before that 2010 deadline.

Other shuttle missions have been delayed by thunderstorms, hurricanes, a faulty fuel gauge data line connector, and other unpredictable problems.

The space agency is leery of taking chances, however, with many officials preferring to err on the side of safety after the disasters that claimed two space shuttles (Challenger and Columbia) and the lives of 14 onboard them.