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Discrepancy Detected In GPS Time
jones_supa writes that on Tuesday, 26th January, Aalto University's Metsähovi observatory located in Kirkkonummi, Finland, detected a rare anomaly in time reported by the GPS system (Google translation). The automatic monitoring system of a hydrogen maser atomic clock triggered an alarm which reported a deviation of 13.7 microseconds. While this is tiny, it is a sign of a problem somewhere, and does not exclude the possibility of larger timekeeping problems happening. The specific source of the problem is not known, but candidates are a faulty GPS satellite or an atomic clock placed in one. Particle flare-up from sun is unlikely, as the observatory has currently not detected unusually high activity from sun.
...disregard it if it continues to exhibit faulty timing.
'course, there really should be a way to correct time in a GPS satellite, if only to avoid making them completely disposable (then again, maybe there is a mechanism to correct/self-diagnose timing issues on-board? One would think/hope so...)
Quo usque tandem abutere, Nimbus, patientia nostra?
It's a hacker or NK trying to start a war.
I think the clock went through a pocket of dark matter and the time dilation caused the time discrepancy.
They where checking if they could skew the accuracy of GPS and if anybody would notice when they did. Oops, somebody noticed.
Well, that's my theory.. Don't ask me who "they" are because I left my tinfoil hat at home today.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Y'heard it here first! Don't tell me I didn't tole ya!
Going back in time by a mere 13.7uS doesn't seem very exciting though.
It's about to get exciting, folks!
Was systemd installed on any of the satellites recently? Maybe it was installed unintentionally, while upgrading the satellite from Debian 7 to Debian 8?
Damn, my $80 dash cam uses GPS time. I'm screwed.
13.7us means about 4km of position error, so yeah, a big deal.
http://www.navcen.uscg.gov/?Do...
Surely if you have more than a couple of satellites in view it will discard the 13.7mS one as a multipath. The chance of it actually giving you a reading thats off by 4km would be quite low I'd say
Mr. President, they are using our own satellites against us and the clock is ticking.
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
This is the second time a bug in the firmware of Motorola Oncore GPS receivers have manifested itself. There is a bug relating to a 32 bit wide bitmap, and DoD just took the GPS satellite numbered 32 out of the constellation and that seems to be the cause. I have data for two such receivers showing the anomaly and for one different receiver seeing no trouble at all.
Poul-Henning Kamp -- FreeBSD since before it was called that...
What the hell are you driving, the Millenium Falcon?
This is why there's redundancy built into the system, more satellites than are strictly needed for operation. If one's clock goes out-of-spec, you notice that it's not agreeing with the rest of the constellation and drop it from your sources. If it's a transient glitch it'll come back in-spec and come back into use, if it's a permanent problem they decommission it and schedule a replacement. Redundancy makes the difference between a major crisis and a minor annoyance.
"(...) reported a deviation of 13.7 microseconds. While this is tiny (...)"
Tiny ? It's huge.
If such an error occurs every hour, the total accumulated error would be more than 7 seconds. It's tiny if you look at it individually (well, not so tiny - your 2GHz CPU clock has a period of 500ps (picosseconds) - that's 0.0000005 microseconds).
The atomic clock period (based on Cs-133) is 108.78278 picosseconds. So this is very very large.
Alvie
Lots of folks on the time-nuts mailing list have GPS-based systems to maintain not only precision time, but also precision frequency standards, and many of them saw and recorded this one.
But it's aliens
Have you ever fallen asleep at the keybhanusdiog?
Reading this, I really feel like I'm living in the future:
"The automatic monitoring system of a hydrogen maser atomic clock triggered an alarm which reported a deviation of 13.7 microseconds."
-Styopa
Agreed, 13.7 microseconds is a substantial error. Large enough that this isn't some obscure esoteric unexplained phenomena; one of the two devices being compared is essentially broken.
It's like reporting that somebody has a car that's supposed to get 30mpg but mysteriously they only get 22mpg. Is it aliens, sunspots, quantum thingamajiggery or just poor maintenance.
Surely if you have more than a couple of satellites in view it will discard the 13.7mS one as a multipath. The chance of it actually giving you a reading thats off by 4km would be quite low I'd say
What if you're coming out of a tunnel or out of a parking garage?
Do not look into laser with remaining eye.
I'm more worried about the USS Eldridge...
Do not look into laser with remaining eye.
My son borrowed the MF. I'm going to have to have a talk with him. He hasn't been his old self lately, its like he's joined some kind of cult. Well, I'm sure it will go ok.
When the atomic clocks in GPS satellites have a discrepancy, you don't report a discrepancy. You report you have done some experiments that suggest faster than light travel across some 30 km apart in the Swiss Alps. By the time they track it down and attributed to some discrepancy in some atomic clock, you got your headlines, the 15 minutes of fame.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
A GPS clock comes with the time already set. Your private rubidium clock needs someone to tell it what time it is, which is probably going to be GPS-based anyway.
God is messing with space time getting ready for the rapture!
Chuck Norris did some push ups so aggressivly that in contrast to his normal work out he liftet his body upwards and did not push the earth down,
thus generated a gravitational wave hitting the gps satellite.
The other explanation is:
It is a black hole and we all are doomed.
Clock speeds are sensitive to the structure of the gravitational field. Maybe other aspects of the Universe.
GPS times have all sort of noise. Some geophysicists use this "noise" to figure things like the atmospheric temperature and density. The GPS signal wavefront bend slightly then. You can tomographically invert for spatial location of the travel time anomalies to locate temperature and density changes. There are papers on this every year at the American Geophysical Union meeting.
Microsecond size anonalies are huge and may have more mudane causes like software.
It's not a problem unless all four corner days are off and thus the four corners of the cube.
Its 2016. We have a widely available set of external reference signals from multiple governments running multiple satellites providing redundant sources of a stable reference. It is far more sensible to use something highly accurate and easily available than spend many thousands of dollars rolling your own.
Except he is using GPS as a very precise 10MHz signal, not a clock. The private rubidium clock (about 1500USD from memory) will provide that very nicely.
Personally if I was running an experiment that required that sort of precision then the private highly accurate frequency source is going to be fairly small beer in the total cost of the experiment and freezes you from the trouble of getting the GPS signal into your lab, which for most labs I know is going to be a right pain in the backside because GPS signals don't extend indoors. Further more is there is not chance that some random event won't knock it out for a few seconds and potentially ruin your experiment.
I guess the point is that until recently using GPS was a valid way to get a very high precision reference frequency, though here in the UK I would suggest that using the BBC Radio 4 LW signal might have been a better idea. The carrier frequency is controlled by a rubidium atomic frequency standard for the express purpose of enabling it to be used as an used as an off-air frequency standard. However time and tide move on and now it is not such a valid choice as it was previously.
The activation of the Large Hadron Collider with full power this past year has ripped a hole in the space time continuum and has been jumping the planet forwards in time by nanoseconds, now milliseconds. If the rift is not contained it will eventually grow exponentially from seconds, minutes, hours, days, months, years, centuries, millenniums to eventually eons, and may forward us in time past the moment of when Sol had collapsed killing us all!!!
GPS is not a particularly stable frequency reference over the short term due to atmospheric distortions and various other noise sources. However, over the long-term it is outstanding.
The normal process is to use a very high quality short-term stable oscillator, e.g. a temperature controlled quartz crystal oscillator - but discipline it to the long-term stable GPS signal. Over periods of hours to days, the quartz oscillator can drift in frequency due to aging, shifts in environmental factors which affect the regulated temperature, etc. By averaging the deviation of the local oscillator from the GPS reference over a suitable period, and gradually tuning the local oscillator to null that error, you can get a frequency with the short-term stability of top-quality quartz, with the long-term stability of GPS.
A similar principle is used with atomic clocks - the atomic reference is used to discipline a good quality quartz oscillator. However, the long term stability of rubidium clocks is several orders of magnitude worse than GPS, hence it is common to find many capable of being disciplined by GPS, or an alternative very high stability atomic source (such as a caesium clock, or hydrogen maser).
Except he is using GPS as a very precise 10MHz signal, not a clock. The private rubidium clock (about 1500USD from memory) will provide that very nicely.
$1500 clock vs. $100 clock. Hmmm. And how do you know the shift was 13.7ms as TFA reports unless you know which clock is right?
and freezes you from the trouble of getting the GPS signal into your lab, which for most labs I know is going to be a right pain in the backside because GPS signals don't extend indoors.
I understand they're developing a solution to that problem, and it will be distributed once the patent has been issued. They're taking a wire, surrounding it with some insulation, then around that goes a mesh of copper to make a second conductor, and then around that all more insulation. I hear they're calling it cropaxial cable or something like that. They claim, but I don't believe it, that you can actually put the GPS antenna outside the building while having the receiver inside! What will they think of next?
I guess the point is that until recently using GPS was a valid way to get a very high precision reference frequency,
Still is.
I've been running a GPS in the lab for almost two decades. Maybe I need to file with the patent office showing "prior art"?
Aliens. Wait, Bigfoot. WAIT, ALIEN BIGFOOTS!!!!11!1!!!1
Fascism: An authoritarian and nationalistic right-wing system of government and social organization. See also: NAZI's
The troublesome bird was SVN-23, one of the oldest GPS birds, launched in 1990!
It was the last of the Block IIA birds, and had an expected 8 year lifetime, which it beat by quite a few years!
It featured a combination of cesium and rubidium clocks -- two of each. Now decommissioned -- http://www.navcen.uscg.gov/?Do...
Read more of this bird's interesting history -- http://www.schriever.af.mil/ne...
It looks like the actual problem was a bad data upload; Specifically, some satellites were transmitting incorrect parameters for UTC offset correction. https://www.febo.com/pipermail... is the posting from a gentlemen at Meinberg that has the details. http://www.usno.navy.mil/USNO/... has more information about the time offset parameters (A0 and A1) and how they interact with GPS and UTC time.
According to another message (https://www.febo.com/pipermail/time-nuts/2016-January/095686.html), PRNs 2, 6, 7, 9, and 23 got hit. It is interesting to note that the satellite that was taken out of service this morning (PRN 32) is not in this list. It looks like the decommissioning of PRN32 was quite possibly scheduled (see http://gpsworld.com/last-block...), and even if not, a failure of that specific satellite could not have caused multiple satellites to start broadcasting incorrect offset data.
I'm really looking forward to the postmortem on this.
Time has traditionally been thought of as being a wave like function,
No it is not, as wave like equations are a rather specific category and have nothing to do with how time is currently or traditionally thought of...
The concept had been simplistic: Sometimes time flowed faster and sometimes it flowed slower.
Einstein’s relativity helped predict that flow.
You're over simplifying here, as relativity doesn't describe it like the flow of a river, as the passage of time is not a specific rate for a given location.
For a photon, it’s the constant and highly predictable duration it takes a single photon to cover roughly 186,000 miles.
And yet that is precisely what relatively is based upon, the time it takes photons to travel a distance to different observers.
GPS Programmers actually INTRODUCED error through their calculations based on a very simple misinterpretation of Einstein’s Theory of Relativity by regarding time as an analog function of nature rather than a discrete function of events.
They didn't misinterpret relativity... which would be a different issue from saying relativity is wrong.
And if you're measuring the distance that radio signals travelled, that's a whopping 4 km.
Is this one of those "that's funny" events that lead to world shattering discoveries?
Or just a bug...?
Just patted a passing bird(in orbit)
13 us in GPS is a pretty big or small misalignment, depending on how you look at it - some 4.1 Km. Definitely enough to upset systems like GPS guidance. - Of course most of the time there is plenty of satellite redundancy..
Below the speed of light Special Relativity is one of the most accurate theories in physics - above the speed of light..