Hubble Faces Scientific Hibernation

NASA is struggling to scientifically resuscitate the Hubble Space Telescope and could decide this week that it's too risky to try to revive it before astronauts arrive on a servicing mission next year.

And that flight could be delayed until May if a spare control unit cannot be readied in time for a targeted launch in February.

An independent review team will meet Wednesday to assess the risks involved with further attempts to bring the telescope out of its scientific slumber.

Some engineers fear an attempt to restart a faulty low-voltage power supply on Hubble's Advanced Camera for Surveys could present risk to one of its cameras and plans to repair two others.

Also under examination: the risk involved with a second attempt to turn on a back-up instrument control and science data formatting unit -- a device critical to restarting Hubble science observations.

A decision could be made to keep the observatory in scientific hibernation until NASA can stage its fifth and final Hubble servicing call.

"They are trying to decide which way to go," said Susan Hendrix, a spokeswoman for NASA's Goddard Space Flight Center in Greenbelt, Md. "They don't take anything lightly in the Hubble world."

Hubble dove back into scientific survival mode last week after ground controllers turned on the back-up instrument control and science data formatter, which hadn't been activated since the telescope's 1990 launch.

Its prime unit failed Sept. 27, prompting an automatic shutdown of its main science instruments -- a precautionary measure meant to give engineers time to sort out the trouble.

In a bid to restart science observations, engineers booted up the back-up control unit and 11 other electronics units aboard the observatory.

Two Hubble instruments came back online. But then a low-voltage power supply glitch prompted the Advanced Camera for Surveys to shut itself down.

Hubble's main flight computer then sensed a loss of "keep-alive" power from another data processor and all of the main instruments turned themselves off.

Engineers now think some sort of "electrical event" caused the back-up control unit and an associated computer to reset. But they have not been able to pinpoint the source of the problem, or the exact nature of it. So the focus now is on assessing the risk involved with any further attempt to activate the control unit.

Engineers also are trying to determine whether another attempt to restart the faulty power supply on the Advanced Camera for Surveys could knock the instrument out of commission.

Hubble still is doing astrometry -- the science of measuring the precise location of celestial objects -- with its Fine Guidance Sensor. But all other science observations are on hold.

NASA now aims to launch the servicing mission in February, but it's unclear whether a spare control unit can be delivered to Kennedy Space Center in time to meet that target.

The next launch opportunity would come around May 8. A decision on the launch target could come Nov. 5 when shuttle program managers meet with Hubble counterparts.

ABOUT THE IMAGES: Click to enlarge and save the awesome Hubble Space Telescope images. They were taken by members of previous servicing crews. You can also click the enlarged images to get even bigger views.