06.04.2019 – Week Numbers for the Precise GPS Time System Reset

26 March 2019

Signals transmitted by GPS satellites are a part of the GPS Time system (GPST). The time transmission format from GPS satellites to a receiver includes the transmission of week numbers and the variable responsible for this is limited in size, causing an overflow to occur every 19.5 years (1,024 weeks).

The first cycle of 1,024 GPS weeks began at midnight of January 5 and 6, 1980. The first zero transition happened at midnight GPST time (but not UTC) of August 21 and 22, 1999. This event is known as WNRO (from Week Number Roll Over, meaning the week number counter had run out) and caused some of the older receivers to start working improperly.

Another WNRO is expected to occur on April 6, 2019.

In preparation, we tested our production equipment at the Center of Electromagnetic Measurements in the Engineering School of Information Technologies, Telecommunications and Control Systems at Ural Federal University.

No equipment failures attributed to the reset were detected during testing.

The current software for the ECOM and ARIS controllers allows them to properly process this particular feature found in GPS receivers, preventing imprecise date and time corrections.

The current software version is 12.169 for ECOM platforms (suitable versions are 11.184 and 12.85 or higher) and 1.9.133 for ARIS platforms (suitable versions are 1.8.131 and 1.9.80 or higher).

Week Numbers for the Precise GPS Time System Reset

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