Software Glitch Cited in Station’s Communications Failure

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NEW YORK — A main computer failure aboard the international space station knocked out communications between the orbiting laboratory and Earth for a short time Feb. 21, but the station has since recovered, NASA officials said.

One of three command and control computers on the space station failed just before 9 a.m. EST, but a backup kicked in as designed to restore communications with Earth after about an hour.

Since then, each of the three computers has suffered a so-called transition event, in which the primary computer shifts to a backup, but the space station’s main control computers are all operating, NASA officials said. The glitch has occurred four times.

Engineers initially suspected the computer problem was due to commands sent from Mission Control on Earth. Mission Control said it was being “ultra-cautious” with the commands it is sending. Engineers also studied odd signals from computers in the station’s new Tranquility module, delivered by the Shuttle Endeavour in February.

But a software glitch associated with how data are sent home from the space station’s European-built Columbus laboratory is now the lead suspect in the space station’s computer woes, Mission Control said.

“Sounds like some good detective work going on down there,” station commander Jeffrey Williams told Mission Control after hearing the news.

Only the command computers were affected, and the space station’s life-support systems continued to work fine, NASA spokesman Pat Ryan said on NASA TV.

“There’s been no impact to life-support systems on board the space station, so no threat to crew safety,” Ryan said.

The space station’s three main command and control computers work in a tiered setup, with one serving as the prime machine, a second as backup and the third in a standby mode for extra protection. Each of those computers has malfunctioned at one point, and then recovered, Ryan said.

The space station currently has a five-person crew: two American, two Russian and one Japanese. The crew was enjoying a day off when the glitch occurred. Mission Control gave the crew Feb. 24 off to make up for the lost rest period.