The U.S. Space Agency says it will not meet a February 2009 launch date for the fifth and final shuttle mission to the Hubble Space Telescope.

National Aeronautics and Space Administration engineers said the decision came after an assessment of the work needed to get a second data-handling unit for the telescope ready to fly. The unit will replace one that failed on Hubble in late September, causing the agency to postpone the originally scheduled Oct. 14 servicing mission.

"We now have done enough analysis of all the things that need to happen with the flight spare unit to know that we cannot be ready for a February launch," said NASA Astrophysics Division Director Jon Morse. "The February date was an initial estimate, assuming minimal hardware preparations and test durations that are no longer viewed as realistic. We've communicated our assessment to the Space Shuttle Program so it can adjust near-term plans."

No new target launch date has been announced.