Two spacewalking astronauts have tackled one of their toughest repairs to the Hubble Space Telescope - a meticulous fix of a broken camera.
They also installed a new spectrograph that can divine the properties of distant galaxies.
The astronauts spent 6.5 hours outside the shuttle Atlantis on Saturday for the third of five back-to-back spacewalks to upgrade the famous space observatory.
NASA officials had billed Saturday's spacewalk as the "hold your breath" day for Atlantis' ongoing 11-day mission.
But the tasks came off without a hitch, after two earlier spacewalks were beset with balky equipment that required astronauts to improvise.
The repairs are designed to keep the observatory in service for another five to 10 years.
