ISS crew bypass faulty switch to power-up computers



June 16, 2007

NASA said yesterday that four lanes (processing channels) out of six on the two navigational and support computers that had crashed earlier in the week on the International Space Station (ISS) were now operational and may be put back online today.

The two computers, the Russian Central Computer and Terminal Computer, each have three lanes of processing capability, although only one lane is required for operation. All three lanes on each computer had failed, but the ISS crew were able to restore two lanes on each computer.

Two processors, one from each of the computers, could not be restored and will be replaced.

"I think we’re in good shape. We feel like the computers are stable and back to normal. We still have a lot of options to go through to recover these machines. We’ve got a talented group of people to look at attitude control," said ISS Program Manager Mike Suffredini during a press conference on Friday.

Suffredini also said that the power levels to the computers were "just fine. We are in a very good position from a life-support perspective."

A power switch was bypassed by Russian cosmonauts Oleg Kotov and Fyodor Yurchikhin using a cable, which allowed at least four of the computers to re-boot. The computers are expected to be tested in the morning, after they have run overnight.

The navigation computers provide backup attitude control and orbital altitude adjustments. For now, the station’s control moment gyroscopes are handling attitude control, with the shuttle’s propulsion system providing backup.

It is not known what initially caused the computers to fail, but Russian engineers say that it could have been a problem with power supply.

"We have plenty of resources, so we have plenty of time to sort this out," said Suffredini on Thursday.