Astronauts on the space shuttle Atlantis have released the Hubble Space Telescope after a series of spacewalks to repair and upgrade the observatory¹.

阿特兰蒂斯号航天飞机上的宇航员在对哈勃望远镜一系列的修复和升级之后将其释放回太空中。

Astronaut Megan McArthur liberated² the telescope from Atlantis' robotic arm at 0857 EDT (1357 BST), marking the last human contact with Hubble.

Pilot Greg Johnson then used two short burns of the shuttle's thrusters（矫正舱身用火箭） to gently back away from the telescope.

Space shuttle Atlantis is scheduled to return to Earth on Friday.

The crew will now stow（装填，装满） the equipment that helped to hold, position, and connect to Hubble during the repairs.

Later on Tuesday, the crew will perform a further inspection⁴ of the shuttle's heat shield. An inspection on 12 May showed minor⁵ damage to the heat shield tiles（瓷砖）.

The fifth and final Hubble servicing mission brought the number of spacewalks to repair it to 23, involving 16 astronauts in a total of 166 hours of work.

'Ready for action'

Commander Scott Altman told mission controllers in Houston that Hubble was "safely back on its journey of exploration".

He thanked everyone on the ground for their help during five gruelling（繁重而累人的） spacewalks.

"Not everything went as we planned but pulling together we've been able to do some incredible things," he said.

Mission control replied that it was "wonderful to see Hubble, the most famous scientific instrument of all time, newly upgraded and ready for action thanks to you".

Commander Altman was referring to a number of snags（暗礁） that occurred during the spacewalks; on Friday, one of the sets of rate sensing units, or gyroscopes, to be replaced would not fit into its bay. A refurbished（再磨光，刷新） unit had to be installed instead.

On Sunday, mission specialists Michael Massimino and Michael Good had to contend with a handrail（扶手，栏杆） blocking their access to the Space Telescope Imaging Spectrograph (STIS), resorting in the end to tearing it off with brute⁶ force.

But the repair was completed as planned. "It was a very long day supporting [Sunday's spacewalk] and testing the STIS after repair," said Ted³ Gull⁷, deputy principal investigator⁸ for the STIS experiment.

"Now we have to catch up on the changes in commanding to the spacecraft to ensure we can get the best out of STIS for the future," he told BBC News.

The instrument was installed on Hubble in 1997 and worked until 2004.

"We knew the source of the failure, but the STIS was not intended to be repaired in space. And getting those 110-plus screws out, without their floating around inside the Hubble, was a major challenge," Dr Gull explained.

"(It) just shows that a combination of humans and robotics works. We hope to do it for future space missions."

Hubble will undergo（遭受，经历） many tests in the coming weeks, with observations set to resume at the end of the summer.

The hope is that the repairs and upgrades will give Hubble at least five more years of useful life.

One of the simpler tasks during the repair mission was to fit a docking（停靠，接驳） ring that will serve as a point of contact with Hubble sometime after 2020.

A robotic mission will be sent to push the telescope back toward Earth's oceans - a return home for the most famous telescope the world has ever known.