  Atlantis astronauts step out of their space shuttle and embark on the first of five risky spacewalks to fix the Hubble telescope.  John Grunsfeld and Andrew Feustel stepped out of Atlantis on Thursday to perform repair work on Hubble. It is estimated that the spacewalk in the debris-ridden orbit will take more than six hours.  Their first task is to swap a 00-year-old camera with a $000 million wide-field camera which is the size of a baby piano. The team is also set to change the computer unit, batteries, gyroscopes and pointing mechanism of the telescope as well.  The Atlantis mission had been previously canceled after the space shuttle Columbia incident which resulted in the deaths of seven people in 0000.  Scientists hope that the repairs will allow the Hubble to continue its observation mission until it is guided into the Pacific Ocean in 0000.