US space shuttle Atlantis capped an extended 13-day mission to rejuvenate the Hubble Space Telescope today with a flawless landing at Edwards Air Force base in California.
The shuttle touched down under clear blue skies at 8.39am PDT (11.39am EDT/1539 GMT) after foul weather stymied two days of landing attempts at the Kennedy Space Center in Florida.
"Welcome home Atlantis, congratulations on a very successful mission giving Hubble a new set of eyes that will continue to expand our knowledge of the universe," radioed astronaut Greg H. Johnson from Mission Control in Houston.
"It was a thrill from start to finish," replied Atlantiscommander Scott Altman.
Mr Altman and pilot Greg C. Johnson began the hour-long glide back to Earth by firing Atlantis's twin braking rockets to leave orbit, shedding 257 feet per second (78 metres per second) to align the ship for a fiery freefall through the atmosphere.
The orbiter unleashed a thundering double sonic boom over the floor of the Mojave Desert as it streaked over Southern California on its approach to Edwards, where the sound barrier was first broken more than 60 years ago.
Initially appearing from the ground as a pinpoint high over the northeastern horizon, the craft descended silently to the base's main landing strip, touching down with a puff of white-grey smoke as the rear wheels made contact with the runway surface.
"Now we can declare this mission a total success," Nasa's head of space science Ed Weiler told a post-landing news conference.
The Atlantisastronauts were the fifth and final crew to work on the Hubble telescope, which was launched in 1990.
An initial servicing mission in 1993 fixed a problem with the telescope's prime mirror, giving Hubble a unprecedented view of the universe. Its observations have provided evidence of galaxies that formed far sooner than scientists thought possible and of the existence of supermassive black holes at the centers of most galaxies.
Hubble also has shed light on a mysterious anti-gravity force known as dark energy that is driving space apart at an increasingly faster rate and it has identified part of the chemical makeup of the atmosphere of a planet beyond the solar system.
"There is no area of modern astronomical research that hasn't been profoundly affected and changed by Hubble," said Hubble senior scientist Dave Leckrone.
Working in teams of two, Atlantis' four spacewalkers tackled a long list of repairs and upgrades to keep Hubble at the cutting edge of research for the next five to 10 years.
"It's a brand new Hubble once again," said Mr Weiler.
Overcoming a wide array of obstacles, including stripped bolts, stuck screws and tiny fasteners that were never intended to be removed in space, the astronauts installed a new camera and light-splitting spectrograph, repaired two other instruments, replaced positioning gyroscopes and batteries, and attached new protective panels over three of the telescope's instrument bays.
The first images from the refurbished observatory are due in September.
The Atlantiscrew returned with two Hubble instruments earmarked for the Smithsonian Air and Space Museum - the telescope's wide-field camera, which took the first deep field image of a tiny sliver of sky to reveal a cornucopia of ancient objects and a package of corrective lenses that refocused light warped by Hubble's flawed prime mirror.
Nasa has eight shuttle missions remaining before it retires the fleet at the end of next year. Its next flight is slated for launch in less than three weeks.
Reuters