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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.'"
To make sure there is no concurrence from another global measuring system. CT ? Possibly. But is that far fetched ?
Quality Test #87: Can you bend the circuit card more than 10 degrees? If so, to what degree?
If you think I voted for Trump because of this post, you're wrong. I voted for Dr. Jill Stein of the Green Party. Again.
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.
Long ago when my company looked into this, the problem was finding manufacturing facilities that had procedures for it.
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.
Sometimes it's good to get the news later to let the facts reveal themselves. Not everything needs to be tied to the '24 hour immediate news' cycle.
"First they came for the slanderers and i said nothing."
Since the Indians are not experiencing the same failure rate on identical hardware, it seems likely that it's something about the environment in the EU's satellites that is causing the problem. Maybe power supply issues, temperature control issues, or vibration issues.
As you say, lots of things (like test equipment and of course aerospace) are exempt from RoHS so it's unlikely to be that. They will have used the most suitable materials.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
Answer: Each time, I can bend it a little more. I ended the test when I reached 180 degrees. I was unable to go past 180 degrees due to a physical limitation.
Sleep your way to a whiter smile...date a dentist!
"The only property we really wanted from the lead was the lower melting point"
and better wetting
and higher ductility so thermal cycling doesn't crack your joints
and suppression of tin scavenging so your solder bath doesn't strip the gold off your boards
and suppression of whisker growth
and the inhibition of tin pest
along with of course the lower process temperature
it's almost as if a eutectic lead-tin alloy was the ideal material for making solder joints.....
These failures would never have happened with an H5 chronometer. Maybe they should launch with one of those as an additional backup.
No, no they don't
Nothing improves ductility and wetting like lead and to knock tin scavenging on the head you need to do more than dope it with .5% copper or bismuth or whatever. Considering our current propensity for shoving high-pin count BGA packages on top of each other and then sticking them into hot little boxes and then shoving them in our pockets we couldn't have chosen a worse time to drop lead, the rate at which devices are failing due to thermal stress induced cracking is embarrassing.
and it just so happens that lead doesn't leech out of landfill, so it's almost as if the whole exercise was pointless.
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.
NASA had a similar problem years ago. They were testing the component by exposing it to voltage spikes. Passing the test also damaged the component.
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?
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.