Hubble gets key set of repairs

Spacewalking astronauts had to put a refurbished pair of gyroscopes into the Hubble Space Telescope after a brand-new set refused to go in Friday, but scientists were satisfied and confident the observatory would point precisely to ever more distant objects in the cosmos.

Replacing the gyroscopes was the top priority of the repair mission, and the struggle had NASA on edge for two hours.

Thanks to the spacewalkers’ effort, Hubble ended up with four new gyroscopes and two refurbished ones. The telescope also got fresh batteries.

It was the second spacewalk in as many days for the Atlantis astronauts, who once again were bedeviled by problems. On Thursday, another two-man team installed a powerful new camera and a computer data unit, after struggling with a stubborn bolt.

As on Thursday, the astronauts got their work done, but it was harder and took longer than expected. Friday’s spacewalk was one of the longest ever, lasting nearly eight hours.

Michael Massimino, who was working from inside Hubble, and his partner, Michael Good, had no problem removing all six of Hubble’s 10-year-old gyroscopes. But the last set of new gyroscopes wouldn’t fit properly.

Mission Control instructed the men to go get a spare box of gyroscopes from the shuttle. The astronauts successfully installed the refurbished set.

The gyroscopes were the astronauts’ No. 1 task on Friday. Three of the old gyroscopes no longer worked, and two others had been acting up.

Hubble’s deputy senior project scientist, Mal Niedner, said he was not concerned the astronauts had to resort to refurbished gyroscopes. They lack the latest anti-corrosive wiring, but it’s “the difference between an A and an A-plus.”

Even though the spacewalk was running behind, the astronauts pressed on and replaced some batteries.

The hefty nickel hydrogen batteries that came out were built before the telescope was launched in 1990. They come three to a pack, about the size of a big TV with a mass of nearly 500 pounds. The final three batteries will be replaced early next week.

NASA hopes to get another five to 10 years of use out of Hubble, once the Atlantis astronauts plug in all the new equipment. They also will take a crack at fixing two broken instruments this weekend.