U.S. space shuttle astronauts are preparing to release the Hubble Space Telescope back into orbit following a week of hard work by crewmen who fixed and upgraded the observatory.

They completed their final repair Friday when they revived a dormant infrared camera that penetrates the dusty heavens. Astronauts from the U.S. shuttle Columbia finished the Hubble telescope renovation project Friday and packed up their tools.

The U.S. space agency's Hubble project manager, Preston Burch, said Friday they have left the observatory the most scientifically capable it has ever been. "We've got a whole new generation of technology in there now and some more exciting technology on the way in the next servicing mission that's coming up. The observatory, I believe, is fare better than when it was launched," he said.

Over the past week, two alternating pairs of astronauts played surgeon to the Hubble as they floated outside the shuttle, giving the telescope new eyes and the equivalent of a new heart.

The new sight comes from a powerful camera that doubles Hubble's field of vision, improves its sensitivity five times, and doubles its clarity.

The new heart is a more reliable electrical distribution unit to replace a faulty one that could have shut down the observatory. Combined with the installation of more powerful solar wings, Hubble now has a stronger electrical generating system that supports operation of all instruments at once, including more power-hungry ones to come.

In the final repair Friday, crewmembers revived a dormant infrared camera by replacing its failed cooling system. The camera's sensors operate only at frigid temperatures of about minus 200 degrees Celsius. The repair will allow astronomers to see celestial objects obscured by dust because their infrared light passes through.

Preston Burch praised the astronauts for carrying out what he described as the most challenging of all four Hubble servicing missions to date. "There were lots of opportunities for mistakes, lots of opportunities for glitches [breakdowns] to occur, and it was just absolutely flawless," he said. "This crew worked harder than any other crew that we've ever had on any previous mission."

Mr. Burch said initial tests show that all the new Hubble telescope equipment is alive and functioning. However, observations will not begin again immediately. Technicians will spend two months or more calibrating the hardware and taking test images.

The U.S. space agency will stop servicing Hubble in two years. It is designed to operate until 2010, when a shuttle crew will bring it back to Earth.

The crew of the shuttle Columbia is to return to Earth Tuesday.