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The International Earth Rotation and Reference Systems Service (IERS), the organisation which monitors and manages the difference between the atomic Universal Coordinated Time (UTC) and Earth-rotation-based time, UT1, has decided that a further leap-second will be inserted on 30th June 2012 at 23 hours, 59 minutes and 59 seconds. This insertion, the first since 2008, is intended to compensate for the accumulated difference between UTC and UT1, and the fact that the Earth’s rotation is currently running slower than UTC. GNSS systems use time references based on atomic clocks linked to UTC, so it is beneficial to keep these time systems aligned with Earth-rotation-based time.

Testing GNSS systems to see how they manage leap second insertions is crucial, particularly as some of the most critical systems around the world rely on precise time, rather than navigation accuracy. The world’s global financial organisations and major energy and communications systems are just three examples.

Users of Spirent GNSS test equipment have been able to test their systems for leap second events for many years. The test is very straightforward, and can be performed easily and repeatedly. An application note Simulating UTC leap second insertion events
provides the background on leap seconds, how they are documented in the relevant ICD and describes how you can perform the test with ease on a Spirent simulator.