After five successful spacewalks that have left the Hubble Space Telescope more capable than ever, astronauts on the space shuttle Atlantis held a space-based press conference today.

(See “Shuttle Crew’s Repairs Will Leave ‘Best Hubble Ever.’”)

The crew recounted the mission’s unexpected obstacles, advocated for human exploration of space, and turned their eyes to new frontiers—before they’d even returned to Earth.

“In human space flight, as much as we love lower-Earth orbit, it’s time to leave lower-Earth orbit and go out and explore the cosmos,” veteran spacewalker John Grunsfeld said.

Hugs for Hubble

Grunsfeld and fellow crew member Andrew Feustel, who was on his first space mission, were the last humans to work directly on the orbiting observatory. No more manned servicing missions are scheduled or likely.

“We both gave Hubble one last hug before coming inside,” Grunsfeld said. “We knew that [crew member Megan McArthur] was going to be the one to hold Hubble the last time and send it on its way.”

Operating a robotic arm from inside the shuttle, McArthur had let go of the satellite on Monday morning, and Atlantis slowly pulled away (see video below).

The mission successfully installed two new science tools, fixed two ailing ones, and replaced batteries and gyrators. But there were definitely hiccups along the way.

For instance, veteran astronaut Michael Massimino struggled to remove the last of 117 screws on one of the science instruments’ handrails during a repair—the screw that had always been the easiest during his practice sessions on Earth, he said.

“What was really most challenging for me was not to give up hope that we could do it,” Massimino said.

Humans vs. Robots

Grunsfeld said such incidents demonstrated “the extreme utility of having people working in space and accomplishing things that are different than what was expected.”

His comments are an indirect response to calls to replace expensive and dangerous manned missions and spacewalks with robotic missions.

“As we push further out, from lower orbit to the moon, Mars, and beyond, we’re going to have to do this kind of work every single day,” he said.

Not before some hard-earned rest, however.

“We’ve been training for this flight for a couple years now,” McArthur said. “We all feel pretty good about what’s been accomplished, but we’re also looking forward to taking a break.”

The seven-member crew is also looking forward to a call this afternoon from U.S. President Barack Obama—and to returning to Earth on Friday, when the predicted weather conditions should provide for a smooth landing.

The fifth and final trip by shuttle astronauts to the Hubble Space Telescope will leave the historic satellite more capable than it has ever been, senior NASA officials said this week.

A shuttle mission scheduled for mid-October is set to deliver new components and undertake extensive in-space repairs—a first—on broken instruments attached to the orbiting observatory.

With the phase out of NASA’s shuttle program, the trip is almost certainly the last chance for astronauts to tweak and improve the telescope that helped scientists determine the age of the universe—13.7 billion years old—and popularized images of deep space.

“If we actually repair the two broken instruments [a camera and spectrograph] , we’ll be in a position of having five fully functional instruments for the first time since launch” 18 years ago, said Edward Weiler, who leads NASA’s science division.

“We’ll have the best Hubble ever, there’s no question,” Weiler told reporters during a Monday briefing at the Goddard Space Flight Center, in Greenbelt, Maryland.

(Related story: Hubble Telescope Turns 15 [2005])

The mission is designed to extend the telescope’s life by five years. But Weiler said the repairs could keep Hubble working for as many as ten.

Hubble Repairs

Launched in 1990, Hubble was built with handles, foot restraints, and other features to allow astronauts to work on the observatory from space.

Even so, previous servicing missions have involved only installations and removals. The plan to repair a broken camera and a spectrograph tool during next month’s space walk is unprecedented, NASA managers said.

The instruments “were not meant to be repaired … the way we’re doing it,” said NASA shuttle astronaut John Grunsfeld, who has visited Hubble twice during five space missions.

At a press conference Tuesday, Grunsfeld joked: “They’re sending me back, because I left a critical tool inside the telescope, and I’m the only one who knows where it is.”

111 Screws

After the shuttle, named Atlantis, meets up with the telescope next month, astronaut Mike Massimino will replace an electronics-board cover on a Hubble spectrograph that broke in 2004.

Spectrographs measure the light and color wavelengths that come from objects, revealing key information, such as the chemical makeup of celestial bodies and their surrounding gases.

The elaborate repair requires Massimino to remove 111 screws with a tool made specifically for the job.

Additional instruments to be installed by NASA astronauts:

— a new spectrograph more sensitive to ultraviolet color bands, which will allow Hubble to more deeply probe the large-scale structure of the universe;

— new gyroscopes and batteries that will keep the satellite powered and correctly aimed.

— a mechanism for a rocket to attach itself to Hubble and safely guide it back to Earth when the telescope is finally decommissioned.

Safety First

Hubble, which now orbits about 350 miles (550 kilometers) above Earth, has not been serviced since 2002.

Safety concerns following the destruction of the shuttle Columbia in 2003 delayed this final servicing mission, which was originally scheduled for 2004, then 2006.

During the upcoming mission, a second space shuttle—Endeavor—will sit on the launch pad, ready to blast into space and aid the seven Atlantis astronauts in the event of an emergency.

After the Columbia disaster, manned missions were required to have mid-space rescue plans. All previous post-Columbia shuttle missions have gone to the International Space Station, which is considered an adequate mid-space safe haven.

But the space station is too far from Hubble to be part of a rescue, making the second standby shuttle mission necessary.