The final space shuttle flight to the Hubble Space Telescope is to be delayed until next year, after a key instrument on the telescope failed just two weeks before the servicing mission was due to launch.

The breakdown of Hubble's data-handling system has convinced Nasa to postpone the launch of its shuttle Atlantis so that the mission can be reconfigured to fix it, officials announced last night. The delay will cost Nasa an estimated $10 million for every month, or about $40 million in total.

Atlantis had been due to take off for the orbiting observatory in a launch window beginning on October 14, to conduct essential maintenance so that the telescope can continue to operate until its planned retirement date of 2013.

On Saturday, however, Hubble abruptly stopped sending science data back to Earth. The problem was diagnosed as a failure of part of its Science Data Formatter known as Side A, which processes and transmits information captured by five instruments.

While Nasa officials are confident they will be able to override the fault in the short term, they also decided that it would be better to postpone the Atlantis mission so that it could also conduct a long-term repair to the formatter.

Ed Weiler, the associate administrator of Nasa's Science Mission Directorate, said that while the delay was disappointing, it was actually rather fortunate that the fault had not emerged later, once Atlantis had already flown.

“Think about if this failure had occurred two weeks after the servicing mission, we had just put two brand new instruments in and thought we extended the lifetime for five, ten years and this thing failed after the last shuttle mission to Hubble,” Dr Weiler said.

“So in some sense, if this had to happen, it couldn't have happened at a better time.”

Over the next few days, engineers will reconfigure a back-up data formatter, Side B, which has been dormant during the 18 years in which Hubble has been operational, to allow it to transmit data.

This, however, is not a viable long-term solution. “If we just switch over to Side B of the Science Data Formatter, we would be left with a system that has several single-point failures, and that would be a risk to the mission for the long duration,” Dr Weiler said.

“Barring some unforeseen circumstance, our plan right now is to take the delay and put up the new hardware so that we can keep Hubble going as long as possible.

“If we're going to spend the money and take all the risk involved in a shuttle mission we want to make sure that we leave Hubble as healthy as we possibly can and potentially locked in for the next five to ten years.”

It will now take until January to test a new data formatter, and to train Atlantis's crew to replace it. The mission is thus now likely to launch in February. It is anticipated that the repair can happen during one of the mission's five spacewalks that are already scheduled.

The Hubble servicing mission is designed to keep the telescope running until at least 2013, when it will be replaced by the new James Webb Space Telescope.

The delay to the Atlantis mission means that the next space shuttle to launch will be Endeavour, which is scheduled to fly to the International Space Station in November.

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