13 microsecond GPS error causes 12 hours of problems

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Time monitoring company Chronos reports that several companies were affected by a small glitch in Global Positioning System (GPS), when 15 satellites broadcast the wrong time, affecting them for many hour stretches.

Chronos noticed that several GPS signals were 13 microseconds out of sync. While 13 microseconds may seem small – there are 1,000,000 microseconds in each second – such a discrepancy is considered severe. Several Chronos telecoms clients were plagued by system errors for “12 hours.”

The origin of the issues comes from the decommissioning of a satellite named SVN 23, according to the US Air Force (USAF), which managed the GPS system. A spokeswoman with the USAF confirmed the error was caused by a software push to the satellites from “ground system software.”

Telecommunications firms rely on the high accuracy of GPS time measurements to control data flow in their networks. The data of every phone call, for example, is synchronised according to GPS data.

To ascertain the accuracy of the signal it is monitored constantly by redundant systems. When the 13 microsecond error happened, thousands of system warnings went off across a spate of companies.

“The alarms were escalating,” said Prof Charles Curry, Chronos chief executive. “One particular network we have, which is a global network, was seeing alarms from all over the place, all over the world.”

There have been no consequences of this error that were evident to the general public, as all these companies have back-up time tracking systems.

“Last week was an example of something going wrong in a fairly major way,” he said. “I don’t think it’s gone quite that badly wrong since 1 January 2004, when the same satellite vehicle number [SVN], 23, decided to become unhappy.”