The soonest it could be operating fully again is late next week, said Art Whipple, a Hubble manager. At worst, the observatory might remain inactive until astronauts arrive with a replacement part next year.
"We're still optimistic," he told reporters Friday.
Flight controllers at Goddard Space Flight Center in Greenbelt, Md., began the lengthy process of restoring data transmission on Wednesday. Everything was going well, until late Thursday afternoon.
First, a low-voltage power supply problem prevented one of Hubble's cameras from being rebooted properly, and then computer trouble struck and all efforts ceased.
It's too soon to know whether the two problems are related, said Whipple.
"We're in the early stage of going through a mountain of data that has been downloaded over the last 24 hours," he said at a news conference.
Hubble's command and data-handling system for science instruments failed late last month and prevented the telescope from capturing and beaming down data used to create the pictures for which Hubble is known.
Because of the breakdown, NASA delayed its final Hubble repair mission by shuttle astronauts that was set for October. The mission won't happen until at least February, possibly later.
The latest setback is not expected to further delay the shuttle mission, Whipple said.
The recovery efforts involved switching to a backup channel for the command and data-handling system that had been dormant since the telescope was launched in 1990. That part, at least, seemed to go well, Whipple said.
So far, this isn't the longest that Hubble has been inactive since NASA's 1993 mission to correct its blurred vision. In 1999, science operations were halted about six weeks because of gyroscope failures that were remedied by astronauts whose flight quickly followed the breakdown.
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