NASA considers to delay the return of space shuttle Atlantis one more day because of the failure of two Russian computers controlling the positioning of the International Space Station.

According to Mike Suffredini, space station programme manager, from the control centre in Houston, Texas, the issue is not very serious, but the computer glitch must be solved before Atlantis will leave the ISS.

Suffredini said the computers - which were made in Germany by Daimler-Benz - may be especially sensitive to "noise," or variations in an electric signal that can cause static.

He expected the problem to be fixed in the next couple of days. Since the computers failed on Tuesday, thrusters on the Atlantis have been fired periodically to help maintain the space station's positioning.

About an hour and 20 minutes before Thursday morning’s scheduled wakeup call, the crews were awakened by a false alarm on the station. The alarm was triggered by the restart of Russian navigation computers that provide backup attitude control and orbital altitude adjustments.

Flight controllers continue efforts to bring the computers back up to full operation. For now, the station’s control moment gyroscopes are handling attitude control, with the shuttle’s propulsion system providing backup.

This is the second delay that affects Atlantis’s schedule. The return flight was already delayed for two days to allow the crew to repair a portion of a thermal blanket that pulled away from heat-shield tiles during the space shuttle's launch.