Engineers had hoped to have the back in working order Friday after a computer responsible for sending data back to Earth . On Wednesday, a NASA team did from the failed system to an on-board redundant system.

Initial tests showed that the backup system was working well, but the observatory's activation was suspended after they ran into two "anomalies", said Art Whipple, chief of NASA's Hubble systems management office at the , in a press conference late Friday.

Whipple said he could not yet pinpoint the specific problems. "We are in the early stage of going through a mountain of data that's been downloaded over the last 24 hours," Whipple said. "We're fairly certain it was not a configuration error. We are not to the point where we can rule out either transient issues or, for that matter, hard failures. We're just not there yet."

He explained that the problem first surfaced when engineers were switching science instruments from safe mode to operation mode. During the final stages of ramping up the Advanced Camera for Surveys, they detected an incorrect voltage level and suspended the move. Several hours later, the Hubble's main computer detected the loss of a signal from another onboard system and put the science instruments back in safe mode. NASA noted that no one is sure yet if the two incidents are related.

Whipple said that at this point he estimates late next week as the soonest the space telescope would be fully operational. "There's a lot of analysis to be done. A lot of data to go through," he said.