NASA: Hubble Down For At Least A Week

NASA's Hubble Space Telescope plunged back into a scientific coma this week after engineers successfully switched on a critical back-up control unit that had not been turned on since the observatory was launched in 1990.

A subsequent computer problem sent the telescope into a coma-like mode, but project managers say engineers should be able to sort through the trouble and get NASA's flagship observatory back into scientific observations by late next week.

"We remain optimistic at this time for recovering full science operations," said Jon Morse, director of the astrophysics division at NASA Headquarters in Washington, D.C. "But even these best laid plans can encounter some unanticipated difficulties."

Added senior Hubble systems manager Art Whipple: "It was not unexpected that there might be issues."

The 12-ton telescope shut itself down after engineers had gone through a complicated effort to activate a back-up instrument control and data formatting unit.

The prime unit failed Sept. 27, and Hubble automatically shut down science observations from all of its primary science instruments.

The failure prompted NASA to delay the planned Oct. 14 launch of NASA's fifth and final Hubble servicing mission so that a spare could be readied for flight. Seven astronauts will fly the mission aboard shuttle Atlantis in February.

In a bid to restart science observations in the meantime, engineers went through a complicated process to turn on Hubble's back-up instrument control and data formatting unit.

Forty to 50 engineers at the Space Telescope Operations Control Center at Goddard Space Flight Center in Greenbelt, Md., sent thousands of computer commands to reconfigure 11 different electronics units aboard the observatory.

Whipple said all that work went well. It wasn't until engineers began to restart Hubble's slumbering science instruments that trouble cropped up.

The observatory's main planetary camera and its cryogenically cooled near-infrared camera both came back online. But then an incorrect voltage level was detected when commands were sent to power up the Advanced Camera for Surveys and the instrument automatically shut down.

A few hours later, Hubble main flight computer sensed a loss of "keep-alive" power from a NASA Standard Spacecraft Computer that plays a critical role in operating telescope instruments. All of the main instruments automatically shut down as a result.

Hubble still can perform astrometry -- the science of measuring the precise positions of celestial objects in space -- with its Fine Guidance Sensor. But science observations otherwise are suspended until engineers can resolve the problems.

Whipple said engineers and scientists are pouring over data dumped by Hubble computers in an effort to ferret out the root cause of the trouble. He said he expects the observatory can be brought back online by the end of next week.

Hubble's longest shutdown to date: six weeks. That's the length of time the telescope was out of commission prior to a servicing mission in December 1999.