Two shuttle astronauts have completed the first of five spacewalks to repair and upgrade the Hubble Space Telescope.

John Grunsfeld and Drew Feustel spent almost seven hours working on the observatory, and achieved all of their primary objectives.

Chief among these was the installation of a new instrument, the Wide Field Camera 3, which will allow Hubble to see deeper into space than ever before.

They also exchanged a data processing computer that failed last year.

The break-down had left Hubble with no back-up for the unit it currently uses to route all its wonderful images to Earth.

The replacement passed its initial connection tests with flying colours, ensuring Hubble now has full redundancy for its data processing tasks.

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Thursday's spacewalk was not without incident. Before the astronauts could install the Wide Field Camera 3, they had to remove the existing Wide Field Planetary Camera 2. This took some time when a bolt refused to come loose as expected.

The spacewalkers tried a number of different tools; but when they failed to move the bolt also, mission control authorised the astronauts to use as much force as possible.

It was an anxious moment, because had the bolt broken the old camera would have been stuck in place and the new instrument would have had to return to Earth.

"OK, here we go," Feustel said as he forced the bolt. "I think I've got it. It turned. It definitely turned." And then he said: "Woo-hoo, it's moving out!"

Keep up the good work Atlantis and we will continue to wish you the best of luck.