NASA Takes Step Toward Hubble Recovery

NASA aims to wake the Hubble Space Telescope from a scientific slumber over the next week after a successful bid today to turn on a spacecraft computer that had been dormant since the observatory's 1990 launch.

Exactly one month after an onboard failure prompted Hubble's main science instruments to shut down, ground controllers on Saturday will try to power up the planetary camera that has produced most of the observatory's iconic images.

But NASA officials are not yet ready to declare victory in what has been an up-and-down effort to restore Hubble science observations.

"As far as confidence goes, obviously, having had this (shutdown) occur once, we recognize that it can occur again," said Art Whipple, manager of the Hubble Systems Management Office at NASA's Goddard Space Flight Center in Greenbelt, Md.

"So confidence will grow as we get time with this computer operating normally. I mean, this is the first time we've turned it on in 18 years, and we'll have to see how it goes."

NASA's latest round of Hubble trouble cropped up Sept. 27 when a prime instrument control and science data formatting unit crashed, prompting the obseratory to automatically shut down its main science instruments.

The telescope is programmed to go into this type of "safe mode" -- a precautionary measure that gives engineers on thr ground time to sort out the trouble.

The shutdown also prompted NASA to delay until at least February the planned Oct. 14 launch of NASA's fifth and final Hubble servicing mission so a new control unit and associated electronics could be shipped up aboard shuttle Atlantis and installed by its seven-member astronaut crew.

Then last week, an attempt to switch over to the telescope's back-up instrument control and science data formatter ended in yet another shutdown of Hubble main science instruments.

A low-voltage power supply on Hubble's Advanced Camera for Surveys malfunctioned, and an "electrical event" caused the back-up control unit and a spacecraft computer to reset, shutting down Hubble's science instruments in the process.

NASA and an independent review team spent the following week trying to pinpoint the causes of the failures and determine the risks involved with making a second attempt to bring the science instruments back online.

NASA could not immediately determine the exact cause of the problems, and some engineers thought Hubble might be damaged during another attempt to restore science observations. Managers considered keeping Hubble in scientific hiberation until the Hubble servicing crew could be launched on Atlantis.

NASA ultimately opted to give it another shot.

Engineers had determined that a robost assortment of fuses on Hubble would isolate any electrical short or open circuit to a single instrument or system.

Consequently, Whipple said, NASA "would be no worse off" if they tried to revive Hubble and failed. Science observations in that case simply would remain on hold until NASA could launched the Hubble servicing crew.

The back-up control unit reset after the trouble cropped up last week and has been running ever since. Ground controllers turned on the back-up computer today and plan to try to reactivate the Wide-Field Planetary Camera 2 on Saturday.

Then if all goes well, engineers next week would start to bring up the Advanced Camera for Surveys and the Near-Infrared Camera and Multiobject Spectrometer.

The testing of a space Science Instrument Control and Data Handling System, meanwhile, is continuing at Goddard. Hubble managers will know by mid-November whether it will be ready for launch in February.

The next launch opportunity after that would come in early May.

ABOUT THE IMAGES: Click to enlarge and save the awesome shots of the Hubble Space Telescope. They were taken by the crew of STS-103 during a December 1999 Hubble servicing mission.