The other day I was sitting at my desk in my home office
I whipped my Herman Miller Aeron chair around to look at the two small commercial units on my lab bench. The 1PPS LED on the Time Machines TM 1000A had stopped blinking. While I was trying to wrap my poor old head around that, the tiny color LCD display on the Leo Bodnar Electronics LeoNTP right next to it lit up with a red warning message about GPS lock being lost.
My first inclination was to go down to the basement to prepare for the coming apocalypse. Instead, I exercised some rare (for me) restraint and sent a query to Time Nuts - a mailing list for folks even more obsessed with precision timing than I am (they do exist).
In short order, Graham in Austin Texas kindly pointed me to the FAA web site where one can look up NOTAMs, notices of issues possibly affecting aviation and pilots, one of the categories of which is outages in the Global Positioning System. Here's the specific NOTAM he pointed me to.
ZDV DENVER (ARTCC),CO. [Back to Top] !GPS 08/260 (KZDV A0287/18) ZDV NAV GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A 359NM RADIUS CENTERED AT 333345N1063840W (TCS054036) FL400-UNL, 311NM RADIUS AT FL250, 215NM RADIUS AT 10000FT, 223NM RADIUS AT 4000FT AGL, 169NM RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230It took some fu on my part to decode it, but it wasn't that hard.
ZDV ARTCC is the Denver Air Route Traffic Control Center.
333345N1063840W is 33°33'45.0"N 106°38'40.0"W, the location at which the source of the GPS interference is centered, which is smack dab in the White Sands Missile Range in New Mexico. (For a good time, click on the Google Maps link I provided, drop into the satellite view, and drill down until you can see the parking lot where they parked their equipment.)
359NM is 359 nautical miles, an area which includes my home near Denver Colorado.
1809031830-1809082230 is 2018-09-03 18:30 UTC to 2018-09-08 22:30 UTC, which is the time window in which I noticed my clocks losing GPS.
GPS disruption has become enough of an problem that there is now a U.S. Coast Guard web site where you can report issues. Most of them appear to be either user error or product failures. But some of them are probably related to testing of deliberate GPS interference - either as a field tactic or to evaluate their ability to deal with it - by our own military. Or others.
Don't say I didn't warn you.
2 comments:
How long did the interruption last?
I liked the Coast Guard website. Crowdsourcing intelligence gathering on other countries GPS interference testing. Brilliant.
Paul:
I can't say because I don't know when it started. But between the time I first noticed it, and clocks started recovering, it was perhaps twenty minutes. The LeoNTP device announced lock lost while I was watching it, and it came back as soon as I rebooted it, so that would have been a couple of minutes. I don't know the exactly nature of the failure, nor do I now the latency in each clock at which it alarms after having lost GPS lock; some hysteresis is typical in such algorithms.
You have probably read about ships in the Black Sea finding that their GPS units reported that they were miles inland. This is the nature of warfare in the 21st Century.
:John
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