Equipment problems have bedevilled the penultimate space walk to repair the aging Hubble telescope.

太空行走修复老化哈勃望远镜的仪器问题。

Nasa hopes the repairs will give Hubble at least five more years of service

Two astronauts took eight hours to resurrect（复活） a spectrograph（光谱摄制仪） used to study black holes, which was disabled by a power failure five years ago.

Work ran over by 90 minutes due to a tool running low on battery power and a particularly awkward（笨拙的，尴尬的） bolt securing a handrail（扶手，栏杆） that needed to be removed.

A strong yanking（猛拉，猛拔） action loosened it and early tests show the repair a success.

Suspended outside the shuttle Atlantis more than 500km above Earth, the astronauts were delayed by a handrail blocking a cover held by 111 tiny screws that had to be opened.

Within lay the flawed wiring of the Space Telescope Imaging Spectograph (STIS) - when working it splits light into its component¹ parts.

After several failed attempts to unscrew the bolt on the handrail they ended up tearing it off with brute² force.

The astronauts, Michael Massimino and Michael Good, taped the pieces so they would not fly off into space where they could become potentially lethal³（致命的） projectiles⁴ whizzing（旋离） about in orbit around the world.

But there were further delays when a specialist tool designed to remove the screws of the cover plate had to be returned to the shuttle Atlantis to have its worn out batteries replaced with fully⁵ charged ones.

Daily spacewalks

The astronauts upgrading the Hubble Space Telescope have now made four spacewalks in as many days.

They have overhauled⁶（分期检查，翻修） Hubble's broken main camera, installed new a Cosmic Origins Spectrograph (COS).

The astronauts were able to restore the camera's wide field channel, with which most of its astronomical⁷ observations are made.

But the repairs failed to recover the ACS high resolution channel, which may now be down for good - despite hopes it could be retrieved⁸（恢复，寻回） another way.

On Friday, the astronauts struggled to complete a critical repair to the telescope, refurbishing a pair of gyroscopes into the telescope after a new set refused to go in.

Sunday's spacewalk team also endured the eight hour mission of the second day when Michael Massimino felt, at times, "like I was wrestling a bear" completing the tricky⁹ task to replace and correct the telescope's gyroscopes.

Previously¹⁰, only three of the six gyroscopes worked, now Hubble has four brand new sets and two refurbished ones. Only two are needed to orient the telescope properly.

On Thursday, the telescope's Wide Field Planetary Camera 2 was replaced with the Wide Field Camera 3, giving the telescope an even deeper view into space - and back into the history of time.

A data processing unit that failed in 2008 was also replaced.

The fifth and final spacewalk is set for Monday and the telescope will be released from the cargo¹¹ bay of the Atlantis shuttle on Tuesday.