(AP) -- Spacewalking astronauts are about to tackle NASA's No. 1 priority in fixing the Hubble Space Telescope.
Astronauts on Friday morning will try to install six new gyroscopes, which are crucial because they help the telescope point in the right direction.
Although this is the second of five spacewalks, NASA managers listed replacing the gyros as their top priority because three of them are broken. The access to the gyros is kind of tricky.
Atlantis astronauts Mike Massimino and Mike Good will also replace three crucial batteries on the telescope.
On Thursday, astronauts successfully swapped out a nearly 16-year-old camera for a new one the size of a baby grand piano. And they replaced a balky computer data device.
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Explore further: Hubble astronauts begin training