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Galileo Satellites Are Experiencing Multiple Clock Failures (bbc.com)
elgatozorbas writes: According to a BBC article, the onboard atomic clocks that drive the satellite-navigation signals on Europe's Galileo network have been failing at an alarming rate. From the report: "Across the 18 satellites now in orbit, nine clocks have stopped operating. Three are traditional rubidium devices; six are the more precise hydrogen maser instruments that were designed to give Galileo superior performance to the American GPS network. Each Galileo satellite carries two rubidium and two hydrogen maser clocks. The multiple installation enables a satellite to keep working after an initial failure. All 18 spacecraft currently in space continue to operate, but one of them is now down to just two clocks. Most of the maser failures (5) have occurred on the satellites that were originally sent into orbit to validate the system, whereas all three rubidium stoppages are on the spacecraft that were subsequently launched to fill out the network. Esa staff at its technical centre, ESTEC, in the Netherlands are trying to isolate the cause the of failures - with the assistance of the clock (Spectratime of Switzerland) and satellite manufacturers (Airbus and Thales Alenia Space; OHB and SSTL). It is understood engineers have managed to restart another hydrogen clock that had stopped. It appears the rubidium failures 'all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground.'"
" It appears the rubidium failures 'all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground."
Dependent upon what the what the test was designed to do, it either passed or failed. It's probably best not to test it again.
09 F9 11 02 9D 74 E3 5B - D8 41 56 C5 63 56 88 C0 45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
To make sure there is no concurrence from another global measuring system. CT ? Possibly. But is that far fetched ?
It's aliens. And if they like Donald Trump I'd say that's an asset, not a liability.
It's true I tell you, feller at work's next door neighbour read it in the paper.
They are using lead solder in these things I hope? If not, they could be shorting out because of tin whiskers. NASA even has a site devoted to this : https://nepp.nasa.gov/whisker/...
Europeans are the big boys in satellites.
The satellites have backup clocks for the very reason that something like this would happen. It just wasn't expected to happen on this scale, but despite that all satellites apparently have at least one rubidium and one hydrogen clock running. They have successfully gotten one hydrogen clock that wasn't running to run again, and there is apparently no reason to expect either way that the other clocks will or will not get restarted. Somebody in earlier comments mentioned a test that was run that may have induced the failure, so it is a bad test. Add it to the things to not do in the future. But the article seemed a bit light on what the things that can be done are, or what got that one clock working.
My local Mom and Pop newspaper told me that a couple of days ago, I guess it also has news for nerds, and faster than /.
4 clocks can only tolerate 1 failure (if you don't understand this, read https://en.wikipedia.org/wiki/Byzantine_fault_tolerance#Early_solutions), so 2 failures means they don't know what time it is, which means they have failed to have accurate time keeping.
Were the capacitors manufactured about ten years ago? ;-)
Where is your vaunted aryan science, naziboys? Hmmm?
At NASA. They were very eager to have it.
... with the assistance of the clock (Spectratime of Switzerland) ... manufacturer
Seems to be a big blow to the Swiss clock makers' reputation for accuracy and reliability. But rejoice. Maybe those Swiss watches will start to sell for more realistic prices...
Disclaimer: This post is intended to produce whooshing.
Free, as in your money being freed from the confines of your account.
4 clocks can only tolerate 1 failure
That's only true if they fail simultaneously. Since they know one is bad, they can eliminate it before the next one fails. Now if one more fails, they are fine (the other two are still in agreement).
If they have a way of externally checking the correctness then they can have three fail and still be operational, because they know which one is correct.
"First they came for the slanderers and i said nothing."
Would seem to indicate that they are solving the Byzantine General problem within the "clock" itself and the other "clocks" really are just spares, as would be expected of such satellites. Do you really think it is a good idea to launch satillites that rely on timekeeping without including clocks that really are just spares?
https://www.bing.com/search?q=... turns up no result indicating that timekeeping is a Byzantine failure problem. That is, it is possible that a clock either always returns a correct result or an easily proven wrong result like returning a value 0. It is a bad search for this topic, but is the one I started with, so anyone reading this, learn from my mistake and do not use it for researching this topic.
Depends on the kind of the failure. If there is a subtle drift, yes, can be hard to detect the two faulty clock. But if they just stop working, it's easy.
Still the case of two clock drifting away can be detected from ground, because you can measure from a static station on earth and find out if the signal sent from the satellite is correct or not. So I don't see problem even with two fault clock.
That's only true if they fail simultaneously. Since they know one is bad, they can eliminate it before the next one fails. Now if one more fails, they are fine (the other two are still in agreement).
We don't know what happens in case of failure - does the clock give inaccurate time, or does it give no time at all. You could have a design where the clock either works or doesn't work, and you don't need to check them for disagreement at all.
As I read it, they put four clocks on every satellite because these clocks break sometimes, and having for maximises the chances of having at least one that is working.
Hope those that depend on these satellites for navigation don't get lost. ;) :)
This is not true for frequency references, which are the function of the on-board clocks. And they are externally disciplined by the two ground stations, which have an array of Cesium and Active Hydrogen Maser clocks.
The Galileo satellites can operate with only a single atomic clock, at reduced performance. They can operate with two clocks of different types at full performance.
. . . .is what sort of shirt were the clock engineers wearing ??
You are wrong. Please refrain from commenting on things you have no clue about.
And don't get "electrical engineering and physics" clocks (jargon for "frequency reference") with layman and computer science clocks (devices that output a time coordinate relative to some frame of reference). Atomic clocks are *always* clocks only in the electrical engineering/physics jargon sense. They are pure frequency references *only*.
Also, "atomic clocks" are always disciplined. Active Hydrogen Masers (in the ground) are primary references, but you always use several of them together to reduce *jitter* (it is not to "majority vote"). Anything else is disciplined by such masers long-term, and often output far more precise short term frequency references (rubidium oscillators, for example) e.g. due to better phase error measurement characteristics, etc.
In the case of a Galileo satellite down to one clock, it will have somewhat reduced performance, and it *will* still be disciplined by the ground telemetry signal.
Is "started" also not a verb? Also a foreigner here. Just asking to be smarter.
The earliest satellite in the constellation was launched only 5 years ago and is less than half way through it's minimum design life.
Yes failures have so far not knocked any satellites off line but only because of redundancy. There is no information as to if these failures are random or systematic. In either case the redundancy comes into play to prevent well controlled random errors most likely to occur as satellites approach end of life.
A 12.5% failure rate in the core components of a system that has been in place for less than half its design life is alarming by any metric. All the rubidium failures have occurred in satellites that are less than a quarter of the way into their design life.
On the upside, given the go live dates under EU law the rubidium clocks are covered under manufacturer warranty. But the shipping costs are going to be a bastard!
It's the past tense, it's perfectly valid and normal English. "I ended; I am ending; I will end".
They should have used unobtanium clocks, FTFY.
Harrison's Postulate - "For every action there is an equal and opposite criticism"
Began - Ended
Moroff
Your post brings to mind a question I was pondering the other day, which may have useful implications.
Other than the battery, would low pressure damage the components typically used in smartphones? I'm thinking around 2 Kpa or so.
Reversing the polarity of the neutron flow always seems to fix the TARDIS, should work here, too.
The proof that these clock failures aren't the result of some CIA meddling is that they haven't had any actual impact. A foreign government would want to take enough of these clocks offline to make the constellation fail, and they would want to make this happen at a time of their choosing. Ho do a few sporadic clock failures, some of which have already been fixed, benefit anyone?
Years ago working on a NASA spacecraft a hitch developed and we couldn't read the system clock. We informed the mission manager. "-- Great, I'll just go tell the Director we can't do this mission because we don't know what time it is". Never lose your sense of humor.
I was just reading some posts from a guy whose job is building electronics which operate in a vacuum. As in, that's what he does all day. His first #1 tip for building electronics to be used in a vacuum is ...
1) Don't use lead-free solder. Vacuum promotes the growth of whiskers, so lead-free solder always ended up with whiskers for us.
I'll take it from the person who does this for a living.
Just not the British though.
Why don't the British build satellites?
Because they haven't figured out how to make them leak oil yet!
Do not look into laser with remaining eye.
Third Option, 2 clocks disagree, both are discarded because you can't be sure which is correct.
Apocalypse Cancelled, Sorry, No Ticket Refunds
Only in the same sense that both are like saying most people eat three meals a day but I only eat one.
PC's and consumer electronics must be especially alarming then. But turning them off and back on again usually fixes any failure.
Merriam Webster disagrees with you.
Browsing at +1 - no ACs, I ignore their posts. So refreshing!
PC's and consumer electronics must be especially alarming then.
You have no idea how much so. Some of us work in situations where PCs need incredibly high uptime. Not only is it alarming having to go through a powercycle, it can also be incredibly dangerous. This is why we do things like add ECC memory for that 1 in a million random case, multiple PSUs, RAID, etc. Then when we actually have an issue we go through a complete root cause of failure analysis with vendor engineers.
You see when things start costing money, failures (even ones that don't knock the device offline) ARE alarming.
Then by that standard the world should be in a perpetual state of alarm.
Yeah? Well I was in the SAS before I was an astronaut, and he's talking crap.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
So you are implying that the Prince of Darkness Lucas Electric was involved in making these satellites?
Time to offend someone
Both are verbs.
start
Ladies and gentlemen, start your engines!
I often start my car before I put on my seat belt.
I had trouble starting my car this morning, but it started fine yesterday. It usually starts fine.
end:
The exam ends at 3.
Classes ended early today.
I bet she will end the relationship after the trip.
We must end the war on drugs.
Then by that standard the world should be in a perpetual state of alarm.
Not at all. Could your computer kill someone if it needed to be reboot? I know my desktop will be just fine, and there's nothing alarming about it. Hell I can put a bullet through my drive right now and I'll be fine. If on the other hand I have 2 drives fail at once in my NAS I would be very alarmed.
You seem to think that being alarmed has to do with the event. It doesn't. It has to do with the risk which is function of the event and the consequence.
I have had a rubidium clock fail here at home. Nothing to be alarmed about, but then I fixed the problem for $125. Try doing that with a satellite.
That's not the standard you set in your first message. "A 12.5% failure rate in the core components of a system that has been in place for less than half its design life is alarming by any metric." I believe it was.
Just what I was going to say. Trump will take care of the problem. Wait for the Tweet.
In a time of universal deceit, telling the truth is a revolutionary act. George Orwell
Freeze - Froze - Frozen
Squeeze - Squoze - Squozen
When the only tool you have is a claw hammer every problem starts to look like the back of someone's skull.
Sure it is. I specified an exact number of failures in an article about a satellite, I specified the design life of a satellite. The consequence is naturally the damage of a satellite.
Taking a statement out of its context is either showing incredibly poor reading comprehension or that you're bored and just feel like talking shit on the internet. I don't think you're stupid, but I do think you have nothing better to do than waste people's time.
Anyway I've made my point. If you want to continue believing that the failure rate they experienced is not alarming then maybe you should call them up and tell them they are wasting all their money on the investigations and analysis. I'm sure they'll take your comments on board.
There's a big difference between something that is alarming vs. probematic. Just because it isn't alarming doesn't mean they are wasting their time figuring out how to get things back in working order. In fact, one of the reasons it is not alarming is because the can do something to get things back in working order. You're like that guy who said Ray Kurzweil was afraid of death because he is interested in finding ways to avoid the unpleasant thing. I don't like lots of things; doesn't mean I am afraid of them. I do things to fix situations; doesn't mean they are alarming. Or are you alarmed every time something fails and you have to turn it off and back on again?
"Alarm" equates to panic. It is not a waste of time to attempt to set people straight when they use a term inappropriately. I may disagree with C. S. Lewis that the proper term for a waterfall is sublime as opposed to beautiful, but he does have a point. https://www.bing.com/search?q=...
Whether or not alarming equates exactly to the emotion of panic or some slightly different emotion, the term alarming as used in the article is usually used to refer to emotion. When it refers to an actual alarm, it is get an alarm as you yourself have indicated.
So you were infiltrating and destroying IRA cells while building electrical circuits on the side and preparing to get blasted off into space?
It was difficult to fit it in alongside being a forex trader and a best-selling novelist, but when you're a twenty-something you don't need much sleep.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."