Space shuttle Columbia will launch at 1148 GMT on Thursday on a risky mission to overhaul the Hubble Space Telescope.
This will involve the first shutdown of the space telescope鈥檚 power supply during orbit. NASA is confident, but not certain, that it will come back on.
鈥淚t kind of violates a long standing policy in the space business that if something鈥檚 working well, you don鈥檛 turn it off and just hope it comes back on,鈥� said Ed Weiler, NASA鈥檚 head of space science.
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The 12-year-old telescope鈥檚 imaging systems are functioning well, but its power generation unit is not working at full capacity.
Astronauts will replace the power generation unit and fit the telescope with a new instrument called the Advanced Camera for Surveys (ACS). This contains 30 different light filters and three cameras. It will detect light from the ultraviolet to the near infrared range, and scientists estimate it will increase Hubble鈥檚 imaging range by a factor of 10.
鈥淰ery ambitious鈥�
The space walkers will also replace the telescope鈥檚 wing-like pair of solar arrays. They will perform a total of five space walks during the 11-day mission.
When the power is switched off, on 5 March, some of Hubble鈥檚 instruments will be wrapped in thermal blankets to protect them from the cold of space. In the event that the telescope cannot be switched back on, NASA says that it will almost certainly be abandoned.
鈥淲e wouldn鈥檛 plant it if we didn鈥檛 think we can do it. But it is very ambitious. It鈥檚 not easy. We鈥檒l worry all the way,鈥� says Anne Kinney, NASA鈥檚 director of astronomy and physics.