The Discovery astronauts, staging a third and final spacewalk, completed repairs on the Hubble Space Telescope today, achieving "100 percent success," a spacewalker said.
As the fourth-longest U.S. spacewalk came to an end, astronaut Steven Smith paused to thank flight controllers, project scientists and engineers for their support during three back-to-back spacewalks totaling 24 hours and 33 minutes.
"In the last three days we put 13 new [components] in the Hubble Space Telescope with 100 percent success," Smith radioed, floating in Discovery's cargo bay. "Our congratulations to everyone at NASA and the contractor team. The country and the world can be very proud of you."
At his side in the orbital darkness, astronomer-astronaut John Grunsfeld, added: "We hope to see it back in service very soon. And from the crew of Discovery, we'd also like to wish everybody happy holidays and peace on Earth."
Freshly equipped with new gyroscopes, a faster computer, a refurbished guidance sensor and other needed upgrades, the four-story space telescope is scheduled to be released from its service platform in Discovery's cargo bay around 6 p.m. EST Christmas Day.
Astronomers hope to resume astronomical observations in about two weeks, after the new equipment has had time to acclimate to the space environment.
"It's a little too early to be elated, but people are walking very lightly on their feet," said Anne Kinney, senior Hubble scientist at NASA headquarters in Washington. "People are really happy."
Discovery's crew accomplished the top priorities of the 96th shuttle mission during two marathon spacewalks Wednesday and Thursday. Today's spacewalk was a combination of preventive maintenance and outright repair work.
A powerful solid-state data recorder was installed to replace an aging reel-to-reel machine, and an S-band radio transmitter that broke down last year was replaced with a fresh model that had to be attached with many small screws and connectors, causing the astronauts to fall behind schedule.
Earlier, Smith and Grunsfeld installed circuitry that will help engineers improve the performance of a refurbished $13 million fine-guidance sensor that was installed Thursday by spacewalkers Michael Foale and Claude Nicollier.
The Hubble was launched in 1990 with a flawed primary mirror. Its scientific instruments are equipped with corrective optics, but its three guidance sensors, which help the observatory lock onto and track its targets, receive uncorrected light from the periphery of Hubble's vision.
The equipment installed today will help engineers fine-tune the new guidance sensor to achieve extraordinary accuracy.
The final item on the agenda today was installation of insulation panels to improve the telescope's ability to withstand the environmental extremes of space.
But because of time lost during the radio installation earlier, the spacewalkers only installed two of six panels. The rest will be attached during the next servicing mission in 2001.