© ReutersAstronaut John Grunsfeld, STS-125 mission specialist, positioned on a foot restraint on the end of Atlantis' remote manipulator system (RMS), participates in the mission's fifth and final session of extravehicular activity (EVA) as work continues to refurbish and upgrade the Hubble Space Telescope on May 18, 2009.
Atlantis astronauts spent more than 36 hours over five marathon spacewalks to make upgrades and outfit Hubble with new instruments. These included a panchromatic wide-field camera that should be able to see objects formed just 500 million years after the universe's birth in the big bang explosion some 13.7 billion years ago.
Using the shuttle's robot arm, astronaut Megan McArthur gently lifted the 13-tonne observatory from a work platform in Atlantis' payload bay where it had been positioned since Wednesday.
Holding the telescope high overhead, she released Hubble at 8:57 a.m. EDT as the spacecraft soared 350 miles over the planet.
"There are folks who thought we couldn't do this. They told us, 'You're too aggressive,'" said lead flight director Tony Ceccacci. "I don't want to say, 'We told you so,' but, 'We told you so.'"
Atlantis is due to land at the Kennedy Space Center in Florida on Friday.
Watching Hubble resume its solitary voyage in orbit was a bittersweet moment for the U.S. space agency, which has staged four previous shuttle missions to service the observatory, plus a 1990 flight to put it into orbit. The shuttle fleet is being retired next year.
The Atlantis crew completed everything NASA had planned, including the unprecedented repair of two science instruments not designed to be worked on in space. The astronauts, clad in bulky suits and gloves, sometimes struggled with the repair work, and were held up at times by stuck bolts.
'Showtime'
"It's showtime for us now," said Hubble program scientist Eric Smith. "We got everything we asked for."
NASA plans to release the first images from the refurbished Hubble in September, following extensive tests of its cameras, light-splitting spectrographs and other systems.
"I truly believe this is a very important moment in human history, and I think it's an important moment for science," Hubble project scientist David Leckrone said.
"Just using what Hubble's already done as a starting point, it's unimaginable that we won't dramatically go further than that," he added.
Hubble already has changed astronomers' understanding of how the universe formed and is evolving. It found ancient galaxies that formed well before scientists believed it was possible for them to exist.
It also provided evidence of an anti-gravity force known as "dark energy" that is inflating all of space at a faster and faster rate.
"There's almost no area of astronomy that isn't in some way significantly impacted by Hubble," Leckrone said.
Added Smith, "I'm really looking forward to what comes next."
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