NASA makes history with spacewalk, station finale

HOUSTON (Reuters) - NASA astronauts made history twice on Friday, venturing on the final spacewalk of the agency's 30-year shuttle program and completing assembly of the $100 billion International Space Station.

Astronauts Mike Fincke and Greg Chamitoff floated outside the orbiting outpost's Quest airlock for the fourth and final spacewalk planned during shuttle Endeavour's 16-day mission, the next to last in the U.S. space shuttle program.

After Fincke and Chamitoff transferred the shuttle's 50-foot (15-meter) inspection boom to the station, doubling the reach of the station's robotic crane, shuttle commander Mark Kelly called Mission Control in Houston to mark the milestone -- after 12 years of efforts.

"Space station assembly is complete," Kelly said.

It was the last spacewalk that shuttle-bound astronauts will undertake before NASA turns over Endeavour and sister ships Discovery and Atlantis to museums. Space station crew will continue to make spacewalks for maintenance and repair tasks.

Later, Chamitoff used a special camera with a wide-angle "fish eye" lens to photograph the space station and paused to reflect on the event.

"We're floating here on the shoulders of giants," said Chamitoff. "This space station is the pinnacle of human achievement and international cooperation."

The spacewalk was the 159th in support of assembly and maintenance of the station, which began with the robotic attachment of the U.S. Unity node with the Russian Zarya base block in 1998.

Since then, the project of 16 nations has grown to more than 1 million pounds (455,000 kg) of hardware orbiting 220 miles above Earth.

In over 1,000 hours worth of ventures in the dark vacuum of space, dressed in bulky spacesuits and wielding all manner of tools and gadgets, astronauts have steadily bolted the station together.

Its interior has grown to the size of a Boeing 747 jet and the wingspan of its power-generating solar wings would nearly cover the surface of a U.S. football field.

NASA will set yet another orbital milestone later on Friday. Fincke, a veteran of two long-duration stays on the station, will eclipse fellow NASA astronaut Peggy Whitson's record of 377 days in space, more than any other U.S. spacefarer.

BITTER SWEET

Officials have repeatedly used the term "bitter sweet" to describe the current mind-set at NASA.

"I am sad to see the three space shuttles be rolled into a museum here shortly," Kelly said during an in-flight news conference. "I think it's a necessary step so we can go on and do some more exciting things."

NASA plans to save the shuttles' $4 billion annual operating budget and develop new vehicles that can travel beyond the station's orbit where the shuttles cannot go.

In the meantime, NASA astronauts will hitch a ride to the station on board Russian Soyuz capsules, at a cost of about $50 million a seat.

Endeavour and its six-man crew are due to leave the station late on Sunday.

The shuttle delivered the station's premiere science experiment, the $2 billion Alpha Magnetic Spectrometer particle detector, and spare parts.

Landing is scheduled for 2:32 a.m. EDT (0632 GMT) on Wednesday at the Kennedy Space Center in Florida. Shuttle Atlantis is targeted to launch on July 8 for NASA's 135th and final flight.

(Additional reporting by Irene Klotz in Cape Canaveral, Fla.; Editing by Peter Cooney and Philip Barbara)