Time Timing Phase and monitoring system

Resilient sync, timing & phase from the experts for telecoms, energy/power, banking, financial institutions, broadcast, enterprise IT, & defence

Resilient Positioning Navigation & Timing

GNSS (GPS, GLONASS, Galileo & Beidou) & eLoran products including GPS repeaters, jamming detection, simulators, receivers, antennas & infrastructure from Chronos via GPS-World.biz

Chronos' timing & monitoring solutions enable traceable time for financial institutions to comply with MiFID II.


GPS Satellite Vehicle Number (SVN) 23 launched in 1990 was retired from service in January 2016. It had occupied Pseudo-Random Noise (PRN) sequence 32 since 2008. According to NANU 2016008 it was marked unusable at 15:36 UTC on 25th January and decommissioned at 22:00 UTC later that same day. Unfortunately (for reasons not yet fully known) the UTC signal on some satellites was off by 13 microseconds. This Case Study charts the activity undertaken by the Chronos support team during and after this unprecedented GPS anomaly event. For some with long memories this is not the first time that SVN23 has caused a problem. The last time was 1st January 2004.

Chronos operates a 24x7x365 support (Service Support Plan – SSP) desk for nearly 100 timing equipment users in over 50 countries around the globe. The first call into the Chronos support team came at 02:00 UTC from a panicked engineer from Customer A who had been called out of bed by their Network Operations Centre (NOC) reporting alarms at a handful of Microsemi (Symmetricom) SSU2000s. These were disqualifying GPS inputs due to the Maximum Time Interval Error (MTIE) metric being outside of set limits. The customer’s engineer was concerned as three sites had gone into holdover since (at those sites) no backup inputs had been assigned. At this stage it appeared that the GPS error had cleared and the Chronos SSP Manager was able to force the units out of holdover. However the scale of the problem escalated as these sites went back into holdover along with dozens of other sites suffering GPS based timing issues.