Final preparations are under way for NASA's planned launch next week of the space shuttle Atlantis to upgrade the Hubble Space Telescope.

The weather looks promising for the shuttle's planned liftoff May 11 at 2:01 p.m. EDT (1802 GMT) from the Kennedy Space Center (KSC) in Cape Canaveral, Fla.

Shuttle weather officer Kathy Winters predicted an 80 percent chance of favorable weather that day, with a small risk of clouds or showers that could prevent a launch.

If the shuttle is unable to lift off Monday, NASA can try again May 12 and May 13, though there is only a 60 percent chance of favorable weather those days.

"Overall for launch weather here at KSC, it looks best on the first day and then the weather starts to deteriorate," Winters said today during a briefing.

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Atlantis is standing ready at Launch Pad 39A, where ground crews are making final checks and preparations of its payload — a cache of new and replacement hardware and instruments to install on Hubble.

"Currently we're just in the final stages of payload closeouts in final preparation for payload bay door closure this afternoon," said shuttle payload manager Debbie Hahn. "Basically we're in great posture for this launch attempt."

The 19-year-old Hubble Space Telescope is losing steam. Though it is still in use by scientists, it only has one working instrument remaining onboard. The new equipment set to be installed should give it a much needed boost in longevity and ability to collect data.

The shuttle's seven-astronaut crew plans to arrive at Cape Canaveral this afternoon aboard NASA jets flown in from Houston's Johnson Space Center.

Veteran spaceflyer Scott Altman will command the 11-day mission, which is set to include five spacewalks to overhaul the orbiting observatory.

The astronauts plan to install a new camera and other new instruments, as well as replace broken gyroscopes and old batteries. This last planned upgrade should extend Hubble's life by at least five years.

In case anything should go seriously wrong during the mission, a second space shuttle — Endeavour — is ready to lift off from Launch Pad 39B to rescue the crew if needed.

This backup plan is unusual, because most shuttle missions are headed to the International Space Station, where astronauts can take shelter if there is trouble with their own spacecraft.

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