GPS Receiver Testing

Spectracom’s GPS constellation simulators, models GSG 54, 55, and 56 can easily simulate the leap second event of June 30, 2012. A typical test takes less than 35 minutes to set up and run. A sample leap second scenario is available for download. This application note provides background on the leap second event and describes leap second testing with the Spectracom simulator.

Since the official definition of time is based on atomic standards, a leap second is inserted in the UTC time scale to keep it in step with the solar day much like a leap day is used to keep the calendar in step with the seasons. A leap second can be added or removed. It can occur at the end of the day on December 31 or June 30 and must be announced approximately 6 months in advance.

The GPS (and other GNSS) system operates on the principal of synchronized precise time. Every satellite broadcasts “GPS Time” which was in sync with official UTC time at one point. GPS does not reconcile the discontinuity of a leap second in its time scale. It transmits GPS Time along with the number of leap seconds according to GPS Interface Specification IS-GPS-200E (latest June 2010). The responsibility to convert GPS time to UTC falls to the GPS receiver and supporting software.