HOUSTON Astronauts finished the last of five complex spacewalks to refurbish the Hubble Space Telescope on Monday, leaving the 19-year-old instrument at the height of its star-gazing prowess.
Three earlier spacewalks during the shuttle Atlantis' 11-day servicing mission to the bus-sized telescope were beset by frozen bolts and balky equipment that left astronauts cursing and ground controllers scrambling to improvise solutions.
But John Grunsfeld and Andrew Feustel's seven-hour house call to Hubble on Monday went so smoothly that NASA added a final task: replacing some of the telescope's thermal insulation.
It was the last time that human hands will ever likely touch Hubble, due to NASA's plans to retire the shuttle fleet next year.
NASA hopes the improvements will keep Hubble operational until at least 2014 so it can work in tandem with its replacement, the James Webb Space Telescope.
"Hey John, you guys have had a great set of spacewalks. Come on in," shuttle Commander Scott Altman told Grunsfeld after he and Feustel replaced batteries and a sensor on Hubble.
"I'm on my way," Grunsfeld said.
Before returning to Atlantis' airlock, Grunsfeld gave a farewell to Hubble that resembled an address to an old friend.
"I want to wish Hubble its' own set of adventures and with the new instruments we've installed that it may unlock further mysteries of the universe," Grunsfeld said.
The telescope is now "more powerful then ever" and has the ability to divine the mass of black holes and sample the composition of distant planets, said Jennifer Wiseman, chief of exoplanet and stellar astrophysics at NASA's Goddard Space Flight Center.
"It's almost like starting with a brand-new observatory," Wiseman said.
The scientific gains came at a high cost in sweat and toil for Atlantis' astronauts, who logged two of the longest spacewalks in NASA history on the Hubble mission.
On two spacewalks, astronauts removed dozens of tiny screws and clamored inside the telescope's body to remove razor-sharp computer circuit boards that were never designed to be repaired in space, a task that NASA officials likened to brain surgery.
The Atlantis crew plans to release Hubble back into orbit on Tuesday and return to the Kennedy Space Center in Florida on Friday.
Hubble has helped rewrite astronomy text books. Among its key contributions are the discovery that the universe is expanding at an increasingly fast rate and that galaxies formed relatively soon after the Big Bang explosion that created the universe 13.7 billion years ago.
(Additional reporting by Irene Klotz, editing by Philip Barbara)