Each crew aboard the International Space Station discovers more and more about what it takes to live and work in space for long periods of time. This year, the fourth for humans continuously staffing the Station since the arrival of Expedition 1 on November 2, 2000, has proven to be an exceptional example.

"Every challenge for the International Space Station crews, flight control teams and management adds to the knowledge base we need to develop longer spaceflight missions to places like the moon and Mars," said Bill Gerstenmaier, International Space Station program manager. "The work we're doing on Station is directly connected to future exploration missions."

International cooperation grew even closer during Station operations this year, particularly in the planning and execution of spacewalks. In February, the Expedition 8 crew, Commander Michael Foale and Flight Engineer Alexander Kaleri, conducted the first spacewalk from the Station by a two- person crew, without a crewmember left inside. The spacewalk demonstrated these types of spacewalks, using the procedures developed by American and Russian flight controllers working together, could be safe and successful.

Two spacewalks were planned for the next crew, Expedition 9 Commander Gennady Padalka and Flight Engineer Michael Fincke. Within days of their arrival, a breakdown of an external Station component added a third spacewalk to their mission. Then, problems were found in the U.S. spacesuits, and international cooperation came through again. Teams worked out procedures for the crew to wear Russian spacesuits to work on the U.S. side of the complex. They worked closely to combine tools and procedures, even switching between control centers and languages, to complete the successful repair.

Astronauts living aboard the Station have been invaluable in maintaining the facility. With no Space Shuttles to deliver supplies since the Columbia accident in February 2003, repair parts have been shipped via the smaller Russian Progress resupply vehicle. Fincke demonstrated U.S. spacesuits could be taken apart and repaired in space. Normally, a Shuttle would have delivered whole new suits as replacements. Fincke's work, continued by Expedition 10 Commander Leroy Chiao, will restore two U.S. spacesuits to operation.

Foale and Kaleri used a small set of tools to perform the unprecedented repair of a stabilizing gyroscope in their exercise treadmill. A new gyroscope would have been too large to deliver aboard a Progress. "The crews have shown repairing hardware in space with few supplies and equipment is possible," Gerstenmaier said. "Missions far from Earth will benefit from their work," he added.

Research on the Station this year was refocused to directly support the Vision for Space Exploration, with human life science experiments taking on highest priority. One such experiment was the Advanced Diagnostic Ultrasound in Microgravity (ADUM). It was used to develop the remote medical diagnostic and telemedicine capabilities needed by crews on distant exploration missions. Another experiment, called FOOT, evaluates the exercise forces necessary to maintain muscle and bone health on long-duration missions. A related experiment, called Biopsy, continues to study some of the basic fundamental principles involved in muscle atrophy that occurs during spaceflight.

Along with tackling technical tasks, ground support teams did their best to make the astronauts feel at home in space. Mission Control, Houston, kept Fincke in touch with his family as his wife gave birth. Fincke was able to talk from space to his wife using an Internet protocol telephone and private family conferences via satellite.

Chiao cast the first vote in a presidential election from 230 miles above Earth. Through a special law passed in Texas in 1997, astronauts are able to vote electronically from space. Chiao submitted his electronic ballet to his county clerk's office via email.

Another milestone in spaceflight was reached this year when Foale accumulated more time in space than any other U.S. astronaut. He logged 374 days, 11 hours and 19 minutes during his Station and previous missions. The astronauts and cosmonauts serve as test subjects, blazing a trail in understanding what happens to the human body while living without gravity for long periods.

Chiao and Expedition 10 Flight Engineer Salizhan Sharipov will continue to maintain hardware and conduct scientific research for the next six months. The Station has been under construction for six years, since the arrival of the first element, the Russian Zarya module, in 1998. Major assembly is set to resume with the return of the Space Shuttle to flight next year.