NASA astronauts completed the first stage of modifications to the Hubble space telescope at 1348 GMT on Monday, replacing the first of the instrument鈥檚 two solar wings.
A number of repairs and modifications to improve the telescope鈥檚 performance and extend its lifespan are planned for this week.
The astronauts first captured Hubble in a tricky manoeuvre at 0931 GMT on Sunday. The telescope was grabbed using the shuttle Columbia鈥檚 15-metre-long robot arm, while flying 588 kilometres above the Earth. The 12-tonne telescope was then attached to the shuttle鈥檚 cargo bay, which enables it to be rotated and tilted for servicing.
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Two astronauts left the shuttle in space suits at 0627 GMT on Monday and successfully replaced the first of Hubble鈥檚 two solar wings with a more power-efficient design during the seven-hour walk. The second solar wing will be replaced during another walk scheduled for Tuesday.
Mission impossible
The mission was placed in jeopardy just 22 hours after launch on Friday, when a clogged coolant line was discovered aboard the shuttle. Mission control only decided that the problem was not serious enough to cancel the repair project late on Saturday.
The crew was first informed of the decision to go ahead when their wake-up call at 0152 GMT on Sunday morning used the Mission Impossible theme tune.
鈥淵our mission, if you choose to accept it, is to rendezvous and grapple the Hubble Space Telescope and then spend five days massively re-outfitting and upgrading the telescope,鈥� said astronaut Dan Burbank from the ground.
The most daring part of the mission involves shutting down the telescope鈥檚 power supply to replace a power control unit on Wednesday. NASA cannot guarantee that the power will come back on and if it does not the telescope will almost certainly have to be abandoned.
Power boost
But replacing the control unit, along with the telescope鈥檚 solar wings, should increase Hubble鈥檚 power significantly. It will allow different instruments to function simultaneously and provide more varied data.
On Thursday astronauts plan to install an instrument called the Advanced Camera for Surveys (ACS). This consists of 30 different light filters and three cameras that detect light from the ultraviolet to the near infrared range. Scientists estimate it will improve Hubble鈥檚 imaging range by a factor of 10.
The final space walk will take place on Friday when astronauts attempt to reactivate an infrared imaging instrument that has failed to function properly.