The International Space Station lost contact with ground controllers because of a computer problem but its commander says the crew is fine, NASA says.
The agency said flight controllers in Houston were updating software on board the station's flight computers on Tuesday when one of the station's data relay systems broke down.
The primary computer that controls critical station functions defaulted to a backup computer, but it was not letting the station communicate with NASA's Tracking and Data Relay Satellites, the US space agency said.
Officials in Houston were later able to communicate briefly with the crew as the space station flew over Russian ground stations. They instructed them to connect a backup computer to begin the process of restoring communications.
The International Space Station marked its 10th anniversary of continuous human occupation on November 2, 2010. Since Expedition 1 in 2000, the space station has been visited by 204 individuals.
The current crew is made up six men: two Americans, three Russians and a Canadian.