CAPE CANAVERAL, Fla. -- Spacewalking astronauts hung another bright blue solar wing on the new-look Hubble Space Telescope Tuesday, giving the storied observatory a much-needed power boost as well as a cosmetic makeover of sorts.

What's Next: Tonight in Space

NASA's flagship Hubble Space Telescope will be shut down in orbit for the first time Wednesday before spacewalking astronauts attempt to swap out the electrical heart of the observatory. And in what could be a disaster in the making, NASA officials are not entirely sure ground controllers will be able to power the telescope back up. Look for John Grunsfeld and Rick Linnehan to set out about 1:30 a.m. EST (0630 GMT) on a spacewalking bid to remove and replace the telescope's Power Control Unit. Similar to a household breaker box, the power switching station routes electricity from Hubble's solar wings to its science instruments, control systems and batteries. A failed change-out, meanwhile, could leave Hubble a powerless piece of space junk. Click here for mission updates and live NASA TV coverage beginning at 1 a.m. EST (0600 GMT) Tuesday.

Chatting constantly outside shuttle Columbia, James Newman and Michael Massimino outfitted Hubble with a second new solar panel -- the twin of a high-efficiency array installed by a different pair of spacewalkers Monday.

Smaller, sturdier and significantly more powerful than Hubble's old gold wings, the $19 million set of solar panels endowed the telescope with a new outward appearance and enough electrical output to run the observatory through its retirement in 2010.

"We show completion with the installation of two new powerful solar arrays to bring Hubble into the future," said astronaut John Grunsfeld, a mission specialist who directed the spacewalking work from inside Columbia's crew cabin.

"We really hope that they'll give us a nice, long science lifetime on Hubble Space Telescope," added NASA astronomy chief Anne Kinney.

The second of five planned Hubble spacewalks this week got underway at 1:40 a.m. EST (0640 GMT) as Columbia rocketed through orbit at 25 times the speed of sound, the massive telescope mounted on a work stand in the back of its Earth-facing cargo bay.

Setting out on his fifth career spacewalk, Newman exited the shuttle's airlock first as Columbia flew 362 miles (579 kilometers) above North Africa, ready to swing out over the Indian Ocean.

"Good to be back," he said. "Beautiful day for a spacewalk."

Newman became the 15th NASA astronaut to head out on a Hubble servicing spacewalk, this one the 15th such excursion in the past nine years.

Rookie astronaut Michael Massimino followed his colleague into Columbia's cargo bay, an ear-to-ear grin evident beneath his helmet as he took in a panoramic view of the planet below.

"This is incredible," Massimino said.

"Welcome to the wonderful world of spacewalking," Grunsfeld replied.

"Thank you, John," Massimino said. "Let's start with my first task."

And with that, the two spacewalkers charged ahead with the prime job at hand: Removing Hubble's portside solar wing and replacing it with the new array.

Built at less than half the cost of the old $40 million arrays, the new wing and its twin are rigid and unfold like books, offering more stability than their flexible, roll-up predecessors.

They are a third smaller, stretching just 25 feet (7.5 meters) -- rather than 40 feet (12 meters) -- from tip to tip. And while they are almost twice as heavy, the 640-pound (288-kilogram) panels are capable of producing 20 percent more power than the old wings.

The extra electrical output will enable astronomers to operate as many as four Hubble instruments simultaneously, speeding the rate at which the observatory can shed light on the origin, evolution and fate of the universe.

The old wings, at the same time, were fast reducing Hubble's ability to study planets, stars and other celestial objects. Damaged by cosmic radiation over the past nine years, their electrical output had dropped to 65 percent of original power.