In case you missed it, there was a significant GPS signal interruption on January 25, 2016, that extended into January 26th. Many of our customers understand the potential impact of GPS signal loss.
As soon as we found about it, Empowered by Optm’ Customer Support proactively reached out to many of our customers to check whether they were impacted by the outage, and provide support in correcting the issue. Our friends at Microchip, based on satellite tracking data from their facilities in San Jose, Boulder, Beverly and Munich, flagged the issue to us early on January 26th.
The likely cause?
For inquiring minds, we’ve since pieced together the likely cause of the outage. A NANU message flagged us that SVN 23 was decommissioned at approximately the time that the outage commenced. On further digging, we found a press release that explained more of the situation.
“Further investigation revealed an issue in the Global Positioning System ground software which only affected the time on legacy L-band signals. This change occurred when the oldest vehicle, SVN 23, was removed from the constellation.”
Since most timing & synchronization applications use L-band GPS signals, we believe this combination of events explains why some of our customers experienced issues.
Back to Normal
Microchip quickly confirmed that the GPS signal anomaly is cleared, and all Microchip systems designed to receive GPS should auto-correct, and lock to GPS without further intervention.
Most reported incidents involved the Microchip SSU-2000 system (because it is the most broadly deployed timing system worldwide) and in all cases, the SSU-2000 either intelligently rejected the faulty GPS signal and switched to an alternate input source, or went into holdover mode.
GPS anomalies like this are very rare, but serve as a good reminder of the needs for a solid backup strategy for GPS outages. That might include having a Cesium Primary Reference Source (PRS) as an alternate input, and/or one or more Rubidium (Rb) oscillators in the SSU-2000.
Empowered customers, if your Microchip system is not locked to GPS, please contact Customer Support at 1.877.325.1855 or firstname.lastname@example.org
Here’s some general actions we recommend for all users:
- Check in on your timing & synchronization systems regularly, to confirm normal operations. If functioning normally, systems should be locked to GPS, with no alarms.
- When (not if) a system goes into holdover mode, your system should raise some form of alarm, or alert, for system administrators, to determine whether action is needed. Empowered Customer Support can provide help to all customers of Microchip / Symmetricom products.
- Engineer and deploy an appropriate backup strategy for GPS. Depending on your application, you may want to consider rubidium (Rb) oscillator upgrades, a Primary Reference Source (PRS), and/or alternate synchronization sources, like Precision Time Protocol (PTP).
While this recent event was corrected in a reasonable timeframe, you need to protect yourself against more serious or lengthy GPS outages. Contact us if you’d like to know more.
Ken Bourne is Director, Timing & Synchronization at Empowered by Optm. Ken has extensive expertise in Synchronization design and implementation, working with Service Providers, Government, Power Utilities, and large Enterprise networks. Empowered has been helping industry synchronize their networks for 20+ years.