WASHINGTON (AFP) – Astronauts from the US shuttle Atlantis Monday concluded the third and final spacewalk of their mission to maintain and install more high-tech equipment on the International Space Station.

The walk, delayed by an hour so that the seal of the water bag inside astronaut Robert Satcher's space suit could be fixed, wrapped up at 1906 GMT for a total of five hours 42 minutes.

NASA downplayed what it called a "drink valve malfunction" with the water bag -- located inside the suits to allow astronauts to drink during their walks -- with space station flight director Brian Smith describing it as "no big deal."

"We had another great day today," Smith told reporters. "We managed to complete all the objectives we had planned for this mission."

Mission specialists Randy Bresnik and Satcher spent the night in the station's Quest airlock as part of the overnight "campout" procedure that helps purge nitrogen from their bloodstreams, preventing decompression sickness once they move out to the vacuum of space.

Spacewalk veteran Mike Foreman assisted the pair in their activities and coordinated communications between them and Mission Control in Houston, Texas, according to the US space agency.

Among the astronauts' tasks Monday was the installation of a high-pressure oxygen tank for the Quest airlock, installed on the orbiter in 2001.

The astronauts also installed a unit to conduct experiments to better understand the effects of space, extreme temperature and solar radiation on composite materials and advanced electronics.

The second spacewalk on Saturday, executed by Bresnik and Foreman, was shortened by about 30 minutes due to false depressurization and smoke alarms, but the duo completed all their scheduled tasks in six hours and eight minutes, according to NASA.

They installed a cargo attachment system on the space-facing side of the station's Starboard 3 truss and set up a wireless video system to transmit images to the station and relay them to Earth.

During a separate mission next year, the Alpha Magnetic Spectrometer will be installed at the attachment point.

Prior to the second spacewalk, two other astronauts used the station's robotic arm to transfer a cargo pallet containing 10,000 pounds (4,545 kilograms) of spare parts.

Bresnik undertook Monday's spacewalk buoyed by a happy event in his personal life. On Sunday night, his wife back on Earth gave birth to a baby daughter, Abigail, NASA announced.

The National Aeronautics and Space Administration said it was the second time a baby had been born to a US astronaut during a space flight. In June 2004, astronaut Mike Fincke's daughter was born while he was aboard the ISS.

After Atlantis, just six space missions will remain in the shuttle program before the fleet's three orbiters are retired.

NASA's shuttle program is due to be mothballed next year, but the White House could still decide to extend it through 2011 to reduce America's future reliance on Russia for transporting astronauts to the space station.

The shuttle remains the only spacecraft that can carry heavy, bulky equipment that is key to maintaining the ISS, set to remain operational until 2020.

Sixteen countries participate in the ISS program, at a cost of 100 billion dollars with most financing coming from the United States.

The US human space flight program, which swallows up 10 billion dollars of NASA's 18-billion-dollar annual budget, is at great risk of being grounded.

A panel set up by President Barack Obama and tasked with assessing its future has said an additional three billion dollars per year is needed for NASA to meet its goal