Satellite date change has users on guard

For the 24 satellites that make up the Global Positioning System (GPS), the "new year" is arriving next weekend. The internal clocks in those satellites will reset for the first time since the government started launching them in 1978. And that's prompting users to take precautions, ranging from GPS system shutdowns to simply warning employees to be ready for potential problems.

The GPS rollover has been likened to the year 2000 problem. On January 5 to 6, 1980, when the system went live, GPS satellites began counting weeks from zero to 1023. On August 21, the satellite clocks will reset, or "rollover", to zero and start another two-decade count. Federal officials said the government-owned satellite system will keep sending out position and timing data past the rollover date without a hitch. But GPS systems that don't recognise the rollover could fail. GPS systems are well known for providing location information, but they also send out very precise time information used for timing computer networks.

GPS receivers can usually be repaired or replaced quickly, experts said. But users are still being cautious.

JB Hunt Transport, for example, is shutting down the GPS-based systems it uses in about half of its 8500 trucks on August 18 and won't restart them until sometime after the date rollover, said George Brooks, vice president of research and development at the Arkansas-based company.

The GPS systems in the trucks are integrated into the company's back-end systems, and Brooks said he's worried that GPS problems could affect those systems. The satellite data is used to track vehicles, assign orders and optimise the use of the fleet. During the shutdown, the company will rely on a backup satellite-tracking system from Qualcomm in San Diego, which is also installed in Hunt's trucks, Brooks said.

In Delaware, state officials have notified state police and other users of its GPS-based radio transmission system to be aware of the potential for problems, said Richard Reynolds, the state project manager for the radio system.

The state has 10 800MHz transmitters that use timing data from GPS satellites to synchronise the passing of radio transmissions. The vendor, Motorola, had to upgrade the GPS receivers on the three-year-old system to make them compliant. If the GPS system fails, radio transmission range will be limited, Reynolds said.

Some experts aren't worried. "I think everything is going to be fine," said Peter Dana, an independent consultant in Georgetown, Texas. "This is an issue that has been responsibly handled in my view by most of the industry."

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